# controls

## specifications for starting model

NOTE: if you are loading a saved model,
then the following initial values are NOT USED to modify the model.
in particular, you cannot use these to change Y or Z of an existing model.
if you want to do that, see `star_job.defaults`

controls such as `change_Y`

.
however, these are reported in output as the initial values for the star.

### initial_mass

initial mass in Msun units. can be any value you’d like when you are creating a pre-main sequence model.

NOTE: this is not used when loading a saved model. however is reported in output as the initial mass of the star. don’t let that confuse you.

if you are loading a ZAMS model and the requested mass is in the range of
prebuilt models, the code will interpolate in mass using the closest prebuilt models.
if the requested mass is beyond the range of the prebuilt models, the code will
load the closest one and then call “relax mass” to create a model to match the request.
the prebuilt range is 0.08 Msun to 100 Msun, so the `relax_mass`

method is only used for extreme cases. there are enough prebuilt models that the
interpolation in mass seems to work fine for many applications.

```
initial_mass = 1
```

### initial_z

initial metallicity for create pre-ms and create initial model
`initial_z`

can be any value from 0 to 0.04

not used when loading a saved model. however is reported in output as the initial Z of the star.

however, if you are loading a zams model,
then `initial_z`

must match one of the prebuilt values.
look in the `'data/star_data/zams_models'`

directory
to see what prebuilt zams Z’s are available.
at time of writing, only 0.02 was included in the standard version of star.

```
initial_z = 0.02d0
```

### initial_y

initial helium mass fraction for create pre-ms and create initial (< 0 means use default which is 0.24 + 2*initial_z)

not used when loading a saved model or a zams model. however is reported in output as the initial Y of the star.

NOTE: this is only used for create pre-main-sequence model and create initial model, and not when loading a zams model.

```
initial_y = -1
```

### initial_he3

initial mass fraction of he3. Must be smaller than initial_y. (< 0 means use default which is taken as solar scaled such that he4/he3 has the same value as the Sun)

not used when loading a saved model or a zams model.

```
initial_he3 = -1
```

## controls for output

### terminal_interval

write info to terminal when `mod(model_number, terminal_interval) = 0`

.
note: this replaces the obsolete control `terminal_cnt`

.

```
terminal_interval = 1
```

### write_header_frequency

output the log header info to the terminal
when `mod(model_number, write_header_frequency*terminal_interval) = 0`

.

```
write_header_frequency = 10
```

### extra_terminal_output_file

if not empty, output terminal info to this file in addition to terminal.
this does not capture all of the terminal output – just the common items.
it is intended for use in situations where you cannot directly see the terminal output
such as when running on a cluster. if you want to be able to monitor
the progress for such cases, you can set `extra_terminal_output_file = 'log'`

and then do `tail -f log`

to view the terminal output as it is recorded in the file.

```
extra_terminal_output_file = ''
```

### terminal_show_age_units

### terminal_show_timestep_units

### terminal_show_log_dt

### terminal_show_log_age

options are ‘years’, ‘yrs’, ‘days’, ‘secs’, or ‘seconds’ this replaces the old controls terminal_show_age_in_years & terminal_show_age_in_days

```
terminal_show_age_units = 'years'
terminal_show_timestep_units = 'years'
terminal_show_log_dt = .true.
terminal_show_log_age = .false.
```

### num_trace_history_values

any valid name for a history data column, such as `surf_v_rot`

for example if you have rapid rotation at the surface,
you might want to try something like this:

```
num_trace_history_values = 7
trace_history_value_name(1) = 'surf_v_rot'
trace_history_value_name(2) = 'surf_omega_div_omega_crit'
trace_history_value_name(3) = 'log_rotational_mdot_boost'
trace_history_value_name(4) = 'log_total_angular_momentum'
trace_history_value_name(5) = 'center n14'
trace_history_value_name(6) = 'surface n14'
trace_history_value_name(7) = 'average n14'
```

value must be less than or equal to 10

```
num_trace_history_values = 0
```

### trace_history_value_name(:)

write values to terminal

```
trace_history_value_name(:) = ''
```

### photo_directory

directory for binary snapshots used in restarts

```
photo_directory = 'photos'
```

### photo_interval

save a photo file for possible restarting when `mod(model_number, photo_interval) = 0`

.
note: this replaces the obsolete control `photostep`

.

```
photo_interval = 50
```

### photo_digits

use this many digits from the end of the `model_number`

for the photo name

```
photo_digits = 3
```

### log_directory

for data files about the run

```
log_directory = 'LOGS'
```

### do_history_file

history file is created if this is true

```
do_history_file = .true.
```

### history_interval

append an entry to the history.data file when `mod(model_number, history_interval) = 0`

.

```
history_interval = 5
```

### star_history_name

name of history file

```
star_history_name = 'history.data'
```

### star_history_header_name

If not empty, then put star history header info in `star_history_name`

file.
In this case the history file has only data, making it easier
to use with some plotting packages.

```
star_history_header_name = ''
```

### star_history_dbl_format

format for writing reals to `star_history_name`

file

```
star_history_dbl_format = '(1pes40.16e3, 1x)'
```

### star_history_int_format

format for writing integer to `star_history_name`

file

```
star_history_int_format = '(i40, 1x)'
```

### star_history_txt_format

format for writing characters to `star_history_name`

file

```
star_history_txt_format = '(a40, 1x)'
```

### write_profiles_flag

profiles are written only if this is true

```
write_profiles_flag = .true.
```

### profile_interval

save a model profile info when `mod(model_number, profile_interval) = 0`

.

```
profile_interval = 50
```

### priority_profile_interval

give saved profile a higher priority for retention when
`mod(model_number, priority_profile_interval) = 0`

.

```
priority_profile_interval = 1000
```

### profiles_index_name

name of the profile index file

```
profiles_index_name = 'profiles.index'
```

### profiles_data_prefix

prefix of the profile data

```
profile_data_prefix = 'profile'
```

### profiles_data_suffix

suffix of the profile data

```
profile_data_suffix = '.data'
```

### profile_data_header_suffix

If not empty, then put profile data header info here. In this case the profile data file has only data, making it easier to use with some plotting packages.

```
profile_data_header_suffix = ''
```

### profile_dbl_format

format for writing reals to profile file

```
profile_dbl_format = '(1pes40.16e3, 1x)'
```

### profile_int_format

format for writing integers to profile file

```
profile_int_format = '(i40, 1x)'
```

### profile_txt_format

format for writing characters to profile file

```
profile_txt_format = '(a40, 1x)'
```

### max_num_profile_zones

if `nz > this`

, then only write a subsample of the zones.
only used if > 1

```
max_num_profile_zones = -1
```

### max_num_profile_models

Maximum number of saved profiles. If there’s no limit on the number of profiles saved, you can fill up your disk – I’ve done it. So it’s a good idea to set this limit to a reasonable number such as 20 or 30. Once that many have been saved during a run, old ones will be discarded to make room for new ones. Profiles that were saved for key events are given priority and aren’t removed as long as there is a lower priority profile that can be discarded instead. Less than zero means no limit.

```
max_num_profile_models = 100
```

### profile_model

save profile when `model_number`

equals this

```
profile_model = -1
```

### profile_header_include_sys_details

if this is true, profile header includes strings for compiler, build, etc.

```
profile_header_include_sys_details = .true.
```

### write_model_with_profile

if this is true, models are written at same time as profiles

```
write_model_with_profile = .false.
```

### model_data_prefix

prefix of the model data files

```
model_data_prefix = 'profile'
```

### model_data_suffix

suffix of the model data files

```
model_data_suffix = '.mod'
```

### write_controls_info_with_profile

if this is true, the values of the options in the controls inlist are written at same time as profiles

```
write_controls_info_with_profile = .false.
```

### controls_data_prefix

prefix of the control data files

```
controls_data_prefix = 'controls'
```

### controls_data_suffix

suffix of the control data files

```
controls_data_suffix = '.data'
```

### mixing_D_limit_for_log

if max `D_mix`

in mixing region is less than this, don’t include the region in the log
doesn’t apply to thermohaline or semiconvective regions

```
mixing_D_limit_for_log = 1d4
```

### write_pulse_data_with_profile

If `.true.`

, also save model data in a format compatible with pulsation codes.

```
write_pulse_data_with_profile = .false.
```

### pulse_data_format

Format of pulsation data. Current options (case insensitive) are:

`'CAFEIN'`

Format defined for CAFein (Valsecchi et al. 2013).

`'FGONG'`

Format originally defined for the GONG solar model project. A definition was given in 2005 for the CoRoT/ESTA project and GONG itself. MESA’s implementation largely follows this subsequent 2015 definition.

`'OSC'`

Format similar to FGONG originally produced for models from CESAM. Also defined for the CoRoT/ESTA project.

`'GYRE'`

The plain-text format defined for GYRE, which GYRE itself refers to as

`'MESA'`

format.`'GSM'`

The HDF5-based format defined for GYRE.

`'SAIO'`

Format for Saio’s pulsation code.

`'GR1D'`

Format for GR1D, defined in Sec. 3 of the GR1D documentation.

```
pulse_data_format = 'FGONG'
```

### add_atmosphere_to_pulse_data

if true, write atmosphere to pulse files
This is not valid when `atm_option = 'table'`

```
add_atmosphere_to_pulse_data = .false.
```

### add_center_point_to_pulse_data

if true, add point for r=0 to pulse files

```
add_center_point_to_pulse_data = .true.
```

### keep_surface_point_for_pulse_data

if true, add k=1 cell to pulse files

```
keep_surface_point_for_pulse_data = .false.
```

### add_double_points_to_pulse_data

add double points at discontinuities

```
add_double_points_to_pulse_data = .false.
```

### interpolate_rho_for_pulse_data

If true, then get `rho_face`

by interpolating rho at cell center.
If false, then calculate rho_face by `dm/(4*pi*r^2*dr)`

.

```
interpolate_rho_for_pulse_data = .true.
```

### threshold_grad_mu_for_double_point

threshold in grad_mu = dln(mu)/dln(P) for a double point to be written

```
threshold_grad_mu_for_double_point = 10d0
```

### max_number_of_double_points

maximum number of double points to be written (0 = no limit); when this limit is set, double points are chosen in order of decreasing \(|\nabla_\mu|\)

```
max_number_of_double_points = 0
```

### fgong_header

These are the four lines of arbitrary text that appear at the beginning of an FGONG file to describe its contents.

```
fgong_header(1) = 'FGONG file'
fgong_header(2) = 'Created by MESAstar'
fgong_header(3) = ''
fgong_header(4) = ''
```

### fgong_ivers

The version number for the FGONG file, which can only be 300 or 1300.
300 gives the old narrow format `'(1P5E16.9,x)'`

, which
can produce numbers with no space separating them.
1300 gives the ‘wide’ FGONG format `'(1P,5(X,E26.18E3))'`

, as agreed on at the
5th Aarhus RGB workshop (University of Birmingham, UK, October 2015).

```
fgong_ivers = 1300 ! 300 or 1300 only
```

### format_for_OSC_data

float format for `'OSC'`

data format

```
format_for_OSC_data = '(1P5E19.12,x)'
```

### max_num_gyre_points

limit gyre output files to at most this number of points only used when > 1

```
max_num_gyre_points = -1
```

### fgong_zero_A_inside_r

when writing FGONG, if r < this and cell has mixing of some kind, force A = 0 Rsun units

```
fgong_zero_A_inside_r = 0d0
```

### trace_mass_location

location for `trace_mass_radius`

, `trace_mass_logT`

, etc. (Msun units)

```
trace_mass_location = 0
```

### min_tau_for_max_abs_v_location

controls choice of location in model for `max_abs_v`

history info.
can use this to exclude locations too close to surface.
ignore if <= 0

```
min_tau_for_max_abs_v_location = 0
```

### min_q_for_inner_mach1_location

controls choice of location in model for innermost mach 1 history info. can use this to exclude locations too close to center.

```
min_q_for_inner_mach1_location = 0
```

### max_q_for_outer_mach1_location

controls choice of location in model for outermost mach 1 history info. can use this to exclude locations too close to surface.

```
max_q_for_outer_mach1_location = 1
```

### burn_min1

used for reporting where burning zone occur, for example in the pgstar TRho profiles.
see `star/public/star_data.inc`

for details.
must be < `burn_min2`

.
In ergs/g/sec.

```
burn_min1 = 50
```

### burn_min2

used for reporting where burning zone occur, for example in the pgstar TRho profiles.
see `star/public/star_data.inc`

for details.
In ergs/g/sec.

```
burn_min2 = 1000
```

### max_conv_vel_div_csound_maxq

only consider from center out to this location

```
max_conv_vel_div_csound_maxq = 1
```

### width_for_limit_conv_vel

look this number of cells on either side of boundary to see if any boundary k in that range has s% csound(k) < s% v(k) <= s% csound(k-1) i.e. transition from subsonic to supersonic as go inward if find any such transition then don’t allow increase in convection velocity. this implies no change from radiative to convective. the purpose of this is to prevent convective energy transport from moving energy from behind a shock to in front of the shock.

```
width_for_limit_conv_vel = 3
```

### max_q_for_limit_conv_vel

for q(k) <= this, don’t allow conv_vel to grow

```
max_q_for_limit_conv_vel = -1
```

### max_r_in_cm_for_limit_conv_vel

for r(k) <= this, don’t allow conv_vel to grow

```
max_r_in_cm_for_limit_conv_vel = -1
```

### max_mass_in_gm_for_limit_conv_vel

for m(k) <= this, don’t allow conv_vel to grow

```
max_mass_in_gm_for_limit_conv_vel = -1
```

### center_avg_value_dq

reported center values are averages over this fraction of star mass

```
center_avg_value_dq = 1d-8
```

### surface_avg_abundance_dq

reported surface abundances are averages over this fraction of star mass

```
surface_avg_abundance_dq = 1d-8
```

### mass_depth_for_L_surf

only if `use_flux_limiting_with_dPrad_dm_form`

```
mass_depth_for_L_surf = 0d0
```

### conv_core_gap_dq_limit

skip non-convective gaps of less than this limit when reporting convective core size

```
conv_core_gap_dq_limit = 0d0
```

## definition of core boundaries

### he_core_boundary_h1_fraction

If fraction >= 0, boundary is outermost location where h1 mass fraction is <= this value,
and he4 mass fraction >= `min_boundary_fraction`

(see below).
If fraction < 0, boundary is outermost location where he4 is the most abundant species.

```
he_core_boundary_h1_fraction = 0.1d0
```

### co_core_boundary_he4_fraction

If fraction >= 0, boundary is outermost location where he4 mass fraction is <= this value,
and c12+o16 mass fraction >= `min_boundary_fraction`

(see below).
If fraction < 0, boundary is outermost location where c12+o16 is more abundant than any other species.

```
co_core_boundary_he4_fraction = 0.1d0
```

### one_core_boundary_he4_c12_fraction

If fraction >= 0, boundary is outermost location where combine he4+c12 mass fraction is <= this value,
and o16+ne20 mass fraction >= `min_boundary_fraction`

(see below).
If fraction < 0, boundary is outermost location where o16+ne20 is more abundant than any other species.

```
one_core_boundary_he4_c12_fraction = 0.1d0
```

### fe_core_boundary_si28_fraction

For this case, “iron” includes any species with A > 46.
If fraction >= 0, boundary is outermost location where si28 mass fraction is <= this value,
and “iron” mass fraction >= `min_boundary_fraction`

(see below).
If fraction < 0, boundary is outermost location where “iron” is the most abundant species.

```
fe_core_boundary_si28_fraction = 0.1d0
```

### neutron_rich_core_boundary_Ye_max

Boundary is outermost location where Ye is <= this value.

```
neutron_rich_core_boundary_Ye_max = 0.48d0
```

### min_boundary_fraction

Value for deciding boundary regions.

```
min_boundary_fraction = 0.1d0
```

## when to stop

### max_model_number

The code will stop when it reaches this model number. Negative means no maximum.

```
max_model_number = -1
```

### when_to_stop_rtol

### when_to_stop_atol

Relative (`rtol`

) and absolute (`atol`

) error criteria for
target stopping values. To compare how accurately the last
step satisfied a stopping condition, MESA evaluates

```
error = abs(value - target_value)/ &
(when_to_stop_atol + when_to_stop_rtol*max(abs(value), abs(target_value)))
```

and will redo with a smaller timestep if `error`

is greater
than 1. The default values `1d99`

for both guarantee that
`error`

is tiny, so the run terminates as soon as a stopping
condition is reached.

If you wish to use either `rtol`

or `atol`

, you should
change the other to 0 (or your desired value). To see why,
suppose we only set `when_to_stop_rtol = 1d-3`

. Because
`when_to_stop_atol`

is still `1d99`

, `error`

will still
be very small and MESA won’t redo the last step.

```
when_to_stop_rtol = 1d99
when_to_stop_atol = 1d99
```

### max_age

### max_age_in_days

### max_age_in_seconds

Stop when the age of the star exceeds this value in years, days, or seconds. Only applies when > 0.

```
max_age = 1d36
max_age_in_days = -1
max_age_in_seconds = -1
```

### num_adjusted_dt_steps_before_max_age

This adjusts `max_years_for_timestep`

so that hit `max_age`

exactly,
without needing possibly large change in timestep at end of run.
only used if > 0

number of time steps to adjust to prior to hitting max age only used if > 0

```
num_adjusted_dt_steps_before_max_age = 0
```

### dt_years_for_steps_before_max_age

timestep in years

```
dt_years_for_steps_before_max_age = 1d6
```

### reduction_factor_for_max_timestep

per time step reduction limited to this

```
reduction_factor_for_max_timestep = 0.98d0
```

### gamma_center_limit

gamma is the plasma interaction parameter. Stop when the center value of gamma exceeds this limit.

```
gamma_center_limit = 1d99
```

### eta_center_limit

eta is the electron chemical potential in units of k*T. Stop when the center value of eta exceeds this limit.

```
eta_center_limit = 1d99
```

### log_center_density_upper_limit

### log_center_density_lower_limit

Stop when log10 of the center density is above/below the upper/lower limit.

```
log_center_density_upper_limit = 12d0
log_center_density_lower_limit = -1d99
```

### log_center_temp_upper_limit

### log_center_temp_lower_limit

Stop when log10 of the center temperature is above/below the upper/lower limit.

```
log_center_temp_upper_limit = 11d0
log_center_temp_lower_limit = -1d99
```

### surface_accel_div_grav_limit = -1

This is used when do not have a velocity variable.
The acceleration ratio is `abs(accel)/grav`

at surface,
where accel is `(rdot-rdot_old)/dt`

and grav is `G*m/r^2`

.
Stop if the ratio becomes larger than this limit.
Ignored if <= 0.

```
surface_accel_div_grav_limit = -1
```

### log_max_temp_upper_limit

### log_max_temp_lower_limit

stop when log10 of the maximum temperature is above/below the upper/lower limit.

```
log_max_temp_upper_limit = 99
log_max_temp_lower_limit = -99
```

### center_entropy_upper_limit

### center_entropy_lower_limit

stop when the center entropy is above/below the upper/lower limit. in kerg per baryon

```
center_entropy_upper_limit = 1d99
center_entropy_lower_limit = -1d99
```

### max_entropy_upper_limit

### max_entropy_lower_limit

stop when the max entropy is above/below the upper/lower limit. in kerg per baryon

```
max_entropy_upper_limit = 1d99
max_entropy_lower_limit = -1d99
```

### xa_central_lower_limit_species

### xa_central_lower_limit

Lower limits on central mass fractions.
Stop when central abundance drops below this limit.
Can have up to `num_xa_central_limits`

of these (see `star_def.inc`

for value).
`xa_central_lower_limit_species`

contains an isotope name as defined in `chem_def.f90`

.
`xa_central_lower_limit`

contains the lower limit value.

```
xa_central_lower_limit_species(1) = ''
xa_central_lower_limit(1) = 0
```

### xa_central_upper_limit_species

### xa_central_upper_limit

Upper limits on central mass fractions.
Stop when central abundance rises above this limit.
Can have up to `num_xa_central_limits`

of these (see `star_def.inc`

for value).
E.g., to stop when center c12 abundance reaches 0.5, set

```
xa_central_upper_limit_species(1) = 'c12'
xa_central_upper_limit(1) = 0.5
```

```
xa_central_upper_limit_species(1) = ''
xa_central_upper_limit(1) = 0
```

### xa_surface_lower_limit_species

### xa_surface_lower_limit

Lower limits on surface mass fractions.
Stop when surface abundance drops below this limit.
Can have up to `num_xa_surface_limits`

of these (see `star_def`

for value)
`xa_surface_lower_limit_species`

contains an isotope name as defined in `chem_def.f`

`xa_surface_lower_limit`

contains the lower limit value

```
xa_surface_lower_limit_species(1) = ''
xa_surface_lower_limit(1) = 0
```

### xa_surface_upper_limit_species

### xa_surface_upper_limit

upper limits on surface mass fractions
stop when surface abundance rises above this limit
can have up to `num_xa_surface_limits`

of these (see `star_def`

for value)
e.g., to stop when surface c12 abundance reaches 0.5, set

```
xa_surface_upper_limit_species(1) = 'c12'
xa_surface_upper_limit(1) = 0.5
```

```
xa_surface_upper_limit_species(1) = ''
xa_surface_upper_limit(1) = 0
```

### xa_average_lower_limit_species

### xa_average_lower_limit

lower limits on average mass fractions
stop when average abundance drops below this limit
can have up to `num_xa_average_limits`

of these (see `star_def`

for value)

```
xa_average_lower_limit_species(1) = ''
xa_average_lower_limit(1) = 0
```

### xa_average_upper_limit_species

### xa_average_upper_limit

upper limits on average mass fractions
stop when average abundance rises above this limit
can have up to `num_xa_average_limits`

of these (see `star_def`

for value)

```
xa_average_upper_limit_species(1) = ''
xa_average_upper_limit(1) = 0
```

### HB_limit

For detecting horizontal branch. Only applies when center abundance by mass of h1 is < 1d-4. Stop when the center abundance by mass of he4 drops below this limit.

```
HB_limit = 0
```

### star_mass_min_limit

Stop when star mass in Msun units is < this. <= 0 means no limit.

```
star_mass_min_limit = 0
```

### star_mass_max_limit

Stop when star mass in Msun units is > this. <= 0 means no limit.

```
star_mass_max_limit = 0
```

### remnant_mass_min_limit

### ejecta_mass_max_limit

Stop when remnant mass in Msun units is < this. <= 0 means no limit. remnant_mass = star_mass - ejecta_mass ejecta_mass is outermost mass that all has v(k) >= v_escape(k)

```
remnant_mass_min_limit = 0
ejecta_mass_max_limit = 1d99
```

### star_species_mass_min_limit

### star_species_mass_min_limit_iso

### star_species_mass_max_limit

### star_species_mass_max_limit_iso

```
star_species_mass_min_limit = 0
star_species_mass_min_limit_iso = ''
```

```
star_species_mass_max_limit = 0
star_species_mass_max_limit_iso = ''
```

### star_H_mass_max_limit

Stop when star hydrogen mass in Msun units is > this. <= 0 means no limit.

star_H_mass_min_limit replaced by star_species_mass_min_limit star_He_mass_min_limit replaced by star_species_mass_min_limit star_C_mass_min_limit replaced by star_species_mass_min_limit star_H_mass_max_limit replaced by star_species_mass_max_limit star_He_mass_max_limit replaced by star_species_mass_max_limit star_C_mass_max_limit replaced by star_species_mass_max_limit

### envelope_mass_limit

envelope_mass = star_mass - he_core_mass

Stop when `envelope_mass`

drops below this limit, in Msun units.

```
envelope_mass_limit = 0
```

### envelope_fraction_left_limit

envelope_fraction_left = (star_mass - he_core_mass)/(initial_mass - he_core_mass)

Stop when `envelope_fraction_left`

< this limit.

```
envelope_fraction_left_limit = 0
```

### xmstar_min_limit

xmstar = mstar - M_center

stop when xmstar in grams is < this. <= 0 means no limit.

```
xmstar_min_limit = 0
```

### xmstar_max_limit

xmstar = mstar - M_center

stop when xmstar in grams is > this. <= 0 means no limit.

```
xmstar_max_limit = 0
```

### he_core_mass_limit

stop when helium core reaches this mass, in Msun units

```
he_core_mass_limit = 1d99
```

### co_core_mass_limit

stop when CO core reaches this mass, in Msun units

```
co_core_mass_limit = 1d99
```

### one_core_mass_limit

stop when ONe core reaches this mass, in Msun units

```
one_core_mass_limit = 1d99
```

### fe_core_mass_limit

stop when iron core reaches this mass, in Msun units

```
fe_core_mass_limit = 1d99
```

### neutron_rich_core_mass_limit

stop when neutron rich core reaches this mass, in Msun units

```
neutron_rich_core_mass_limit = 1d99
```

### he_layer_mass_lower_limit

he layer mass is defined as `he_core_mass`

- `c_core_mass`

stop when `c_core_mass`

> 0 and he layer mass < this limit (Msun units).

```
he_layer_mass_lower_limit = 0
```

### abs_diff_lg_LH_lg_Ls_limit

stop when `abs(lg_LH - lg_Ls) <= abs_diff_LH_Lsurf_limit`

can be useful for deciding when pre-main sequence star has reached ZAMS
set to negative value to disable

```
abs_diff_lg_LH_lg_Ls_limit = -1
```

### Teff_upper_limit

stop when Teff is greater than this limit.

```
Teff_upper_limit = 1d99
```

### Teff_lower_limit

stop when Teff is less than this limit.

```
Teff_lower_limit = -1d99
```

### photosphere_r_upper_limit

stop when `photosphere_r`

is greater than this limit, in Rsun units

```
photosphere_r_upper_limit = 1d99
```

### photosphere_r_lower_limit

stop when `photosphere_r`

is less than this limit, in Rsun units

```
photosphere_r_lower_limit = -1d99
```

### photosphere_m_upper_limit

stop when `photosphere_m`

is greater than this limit, in Msun units

```
photosphere_m_upper_limit = 1d99
```

### photosphere_m_lower_limit

stop when `photosphere_m`

is less than this limit, in Msun units

```
photosphere_m_lower_limit = -1d99
```

### photosphere_m_sub_M_center_limit

stop when `photosphere_m`

is less than this limit above `M_center`

, in Msun units

```
photosphere_m_sub_M_center_limit = -1d99
```

### log_Teff_upper_limit

stop when log10 of Teff is greater than this limit.

```
log_Teff_upper_limit = 1d99
```

### log_Teff_lower_limit

stop when log10 of Teff is less than this limit.

```
log_Teff_lower_limit = -1d99
```

### log_Tsurf_upper_limit

stop when log10 of T in outermost cell is greater than this limit.

```
log_Tsurf_upper_limit = 1d99
```

### log_Tsurf_lower_limit

stop when log10 of T in outermost cell is less than this limit.

```
log_Tsurf_lower_limit = -1d99
```

### log_Rsurf_upper_limit

stop when log10 of R/Rsun in outermost cell is greater than this limit.

```
log_Rsurf_upper_limit = 1d99
```

### log_Rsurf_lower_limit

stop when log10 of R/Rsun in outermost cell is less than this limit.

```
log_Rsurf_lower_limit = -1d99
```

### log_L_upper_limit

stop when log10(total luminosity in Lsun units) is greater than this limit.
in order to skip pre-ms, this limit only applies when `L_nuc`

> 0.01*L

```
log_L_upper_limit = 1d99
```

### log_L_lower_limit

stop when log10(total luminosity in Lsun units) is less than this limit.

```
log_L_lower_limit = -1d99
```

### log_g_upper_limit

stop when log10(gravity at surface) is greater than this limit.

```
log_g_upper_limit = 1d99
```

### log_g_lower_limit

stop when log10(gravity at surface) is less than this limit.

```
log_g_lower_limit = -1d99
```

### log_Psurf_upper_limit

stop when log10 of surface pressure is greater than this limit.

```
log_Psurf_upper_limit = 1d99
```

### log_Psurf_lower_limit

stop when log10 of surface pressure is less than this limit.

```
log_Psurf_lower_limit = -1d99
```

### log_Dsurf_upper_limit

stop when log10 of surface density is greater than this limit.

```
log_Dsurf_upper_limit = 1d99
```

### log_Dsurf_lower_limit

stop when log10 of surface density is less than this limit.

```
log_Dsurf_lower_limit = -1d99
```

### power_nuc_burn_upper_limit

stop when total power from all nuclear reactions (in Lsun units) is > this.

```
power_nuc_burn_upper_limit = 1d99
```

### power_h_burn_upper_limit

stop when total power from hydrogen-consuming reactions (in Lsun units) is > this.

```
power_h_burn_upper_limit = 1d99
```

### power_he_burn_upper_limit

stop when total power from reactions burning helium (in Lsun units) is > this.

```
power_he_burn_upper_limit = 1d99
```

### power_z_burn_upper_limit

stop when total power from reactions burning metals (in Lsun units) is > this

```
power_z_burn_upper_limit = 1d99
```

### power_nuc_burn_lower_limit

stop when total power from all nuclear reactions (in Lsun units) is < this.

```
power_nuc_burn_lower_limit = -1d99
```

### power_h_burn_lower_limit

stop when total power from hydrogen consuming reactions (in Lsun units) is < this.

```
power_h_burn_lower_limit = -1d99
```

### power_he_burn_lower_limit

stop when total power from reactions burning helium (in Lsun units) is < this.

```
power_he_burn_lower_limit = -1d99
```

### power_z_burn_lower_limit

stop when total power from reactions burning metals (in Lsun units) is < this.

```
power_z_burn_lower_limit = -1d99
```

### max_abs_rel_run_E_err

Stop if the abs value of cumulative_energy_error/total_energy exceeds this value. Ignore if < 0. Also ignore during relax operations.

```
max_abs_rel_run_E_err = -1
```

### max_number_retries

Stop if the number of retries exceeds this value. Ignore if < 0.

```
max_number_retries = -1
```

```
relax_max_number_retries = 300
```

### min_timestep_limit

stop if need timestep smaller than this limit, in seconds

```
min_timestep_limit = 1d-6
```

### center_Ye_lower_limit

stop if `center_ye`

drops below this limit

```
center_Ye_lower_limit = -1
```

### center_R_lower_limit

stop if `R_center`

drops below this limit (in cm)

```
center_R_lower_limit = -1
```

### fe_core_infall_limit

stop if atleast `fe_core_infall_mass`

of material has speed greater than this, at a location interior to `fe_core_mass`

, in cm/s

```
fe_core_infall_limit = 3d7
```

### fe_core_infall_mass

Amount of mass to check if collapsing, the smaller this is the closer the velocity minima will be to `fe_core_infall`

but there will be a greater chance of a
transistent velocity spike causing the model to prematurely exit. In solar masses

fe_core_infall_mass = 0.1d0

### non_fe_core_infall_limit

stop if atleast `non_fe_core_infall_mass`

of material has speed greater than this, at a location interior to `he_core_mass`

and exterior to `fe_core_mass`

. in cm/s

```
non_fe_core_infall_limit = 1d99
```

### non_fe_core_infall_mass

Amount of mass to check if collapsing, the smaller this is the closer the velocity minima will be to `non_fe_core_infall`

but there will be a greater chance of a
transistent velocity spike causing the model to prematurely exit. In solar masses

non_fe_core_infall_mass = 0.1d0

### non_fe_core_rebound_limit

stop if max rebound speed (outward) at any location interior to `he_core_mass`

. in cm/s

```
non_fe_core_rebound_limit = 1d99
```

### v_div_csound_max_limit

stop if any `v/csound`

> this limit

```
v_div_csound_max_limit = 1d99
```

### v_div_csound_surf_limit

stop if `v_surf/csound_surf`

> this limit

```
v_div_csound_surf_limit = 1d99
```

### v_surf_div_v_kh_upper_limit

stop if `abs(v_surf/v_kh)`

> this limit, where `v_kh = photosphere_r/kh_timescale`

```
v_surf_div_v_kh_upper_limit = 1d99
```

### v_surf_div_v_kh_lower_limit

stop if `abs(v_surf/v_kh)`

< this limit, where `v_kh = photosphere_r/kh_timescale`

```
v_surf_div_v_kh_lower_limit = -1d99
```

### v_surf_div_v_esc_limit

stop if `v_surf/v_esc`

> this limit

```
v_surf_div_v_esc_limit = 1d99
```

### v_surf_kms_limit

stop if `v_surf`

in km/s > this limit

```
v_surf_kms_limit = 1d99
```

### Lnuc_div_L_zams_limit

defines “near zams” – note: must also set `stop_near_zams`

```
Lnuc_div_L_zams_limit = 0.9d0
```

### stop_near_zams

if true, stop if Lnuc/L > `Lnuc_div_L_zams_limit`

```
stop_near_zams = .false.
```

### stop_at_phase_PreMS

### stop_at_phase_ZAMS

### stop_at_phase_IAMS

### stop_at_phase_TAMS

### stop_at_phase_He_Burn

### stop_at_phase_ZACHeB

### stop_at_phase_TACHeB

### stop_at_phase_TP_AGB

### stop_at_phase_C_Burn

### stop_at_phase_Ne_Burn

### stop_at_phase_O_Burn

### stop_at_phase_Si_Burn

### stop_at_phase_WDCS

if true, when phase of evolution reaches this point.

```
stop_at_phase_PreMS = .false.
stop_at_phase_ZAMS = .false.
stop_at_phase_IAMS = .false.
stop_at_phase_TAMS = .false.
stop_at_phase_He_Burn = .false.
stop_at_phase_ZACHeB = .false.
stop_at_phase_TACHeB = .false.
stop_at_phase_TP_AGB = .false.
stop_at_phase_C_Burn = .false.
stop_at_phase_Ne_Burn = .false.
stop_at_phase_O_Burn = .false.
stop_at_phase_Si_Burn = .false.
stop_at_phase_WDCS = .false.
```

### Lnuc_div_L_upper_limit

stop when Lnuc/L is greater than this limit.

```
Lnuc_div_L_upper_limit = 1d99
```

### Lnuc_div_L_lower_limit

stop when Lnuc/L is less than this limit.

```
Lnuc_div_L_lower_limit = -1d99
```

### gamma1_limit

stop if min gamma1 < this limit in a cell with `q <= gamma1_limit_max_q`

```
gamma1_limit = -1
```

### gamma1_limit_max_q

stop if gamma1 < this limit at any location with `q <= gamma1_limit_max_q`

values near unity skip the outer envelope

```
gamma1_limit_max_q = 0.95d0
```

### gamma1_limit_max_v_div_vesc

stop if gamma1 < this limit at any location with `v_div_vesc <= gamma1_limit_max_v_div_vesc`

```
gamma1_limit_max_v_div_vesc = 0.95d0
```

### Pgas_div_P_limit

criteria for stopping on Pgas/P

```
Pgas_div_P_limit = 0
```

### Pgas_div_P_limit_max_q

stop if Pgas/P < this limit at any location with `q <= Pgas_div_P_limit_max_q`

values near unity skip the outer envelope

```
Pgas_div_P_limit_max_q = 0.95d0
```

### peak_burn_vconv_div_cs_limit

limits ratio of convection velocity to sound speed at location of peak `eps_nuc`

```
peak_burn_vconv_div_cs_limit = 1d99
```

### omega_div_omega_crit_limit

stop if omega/omega_crit is > this anywhere in star ignore if < 0

```
omega_div_omega_crit_limit = -1
```

### delta_nu_lower_limit

stop when asteroseismology `delta_nu`

in micro Hz is < this. <= 0 means no limit.

```
delta_nu_lower_limit = 0
```

### delta_nu_upper_limit

stop when asteroseismology `delta_nu`

in micro Hz is > this. <= 0 means no limit.

```
delta_nu_upper_limit = 0
```

### shock_mass_upper_limit

stop when shock_mass is > this. <= 0 means no limit.

```
shock_mass_upper_limit = -1
```

### mach1_mass_upper_limit

stop when outer location of mach 1 is > this. <= 0 means no limit.

```
mach1_mass_upper_limit = -1
```

### delta_Pg_lower_limit

stop when `delta_Pg`

in micro Hz is < this. <= 0 means no limit.

```
delta_Pg_lower_limit = 0
```

### delta_Pg_upper_limit

stop when `delta_Pg`

in micro Hz is > this. <= 0 means no limit.

```
delta_Pg_upper_limit = 0
```

### stop_when_reach_this_cumulative_extra_heating

(ignore if <= 0)

```
stop_when_reach_this_cumulative_extra_heating = 0d0
```

## mixing parameters

### mixing_length_alpha

The mixing length is this parameter times a local pressure scale height.
To increase R vs. L, decrease `mixing_length_alpha`

.

```
mixing_length_alpha = 2
```

### remove_small_D_limit

If MLT diffusion coeff D (cm^2/sec) is less than this limit,
then set D to zero and change the point to `mixing_type == no_mixing`

.

```
remove_small_D_limit = 1d-6
```

### use_Ledoux_criterion

a location in the model is Schwarzschild stable when `gradr < grada`

it is Ledoux stable when `gradr < gradL`

, where `gradL = grada + composition_gradient`

note that these are the same when `composition_gradient = 0`

so you can force the use of the Schwarzschild criterion by passing 0 for
the `composition_gradient`

argument to the mlt routine.
that’s what happens if you set the control “`use_Ledoux_criterion`

” to false.

- overshooting and rotational mixing are dealt with separately
and are added after the MLT classifications are made.

```
use_Ledoux_criterion = .false.
```

### num_cells_for_smooth_gradL_composition_term

Number of cells on either side to use in weighted smoothing of `gradL_composition_term`

.
`gradL_composition_term`

is set to the “raw” unsmoothed `brunt_B`

and then optionally smoothed according `num_cells_for_smooth_gradL_composition_term`

.
In cases where the Ledoux criterion is used to evaluate the boundary for burning
convective cores, you may need to set `num_cells_for_smooth_gradL_composition_term = 0`

to avoid smoothing the stabilizing composition jump into the convection zone and
unphysically causing it to shrink. See section 3.2 in Moore, K., & Garaud, P. 2016, APJ, 817, 54

```
num_cells_for_smooth_gradL_composition_term = 3
```

### threshold_for_smooth_gradL_composition_term

Threshold for weighted smoothing of `gradL_composition_term`

. Only apply smoothing (controlled
by `num_cells_for_smooth_gradL_composition_term`

) for contiguous regions where \(|\nabla_L|\) exceeds
this threshold. Might be useful for preventing narrow composition jumps from being excessively
broadened by smoothing

```
threshold_for_smooth_gradL_composition_term = 0
```

### alpha_semiconvection

Determines efficiency of semiconvective mixing.
Semiconvection only applies if `use_Ledoux_criterion`

is true.

```
alpha_semiconvection = 0
```

### semiconvection_option

`'Langer_85 mixing; gradT = gradr'`

: uses Langer scheme for mixing but sets gradT = gradr`'Langer_85'`

: this calculates special gradT as well as doing mixing.

```
semiconvection_option = 'Langer_85 mixing; gradT = gradr'
```

### thermohaline_coeff

Determines efficiency of thermohaline mixing.
was previously named `thermo_haline_coeff`

.
thermohaline mixing only applies if `use_Ledoux_criterion`

is true.

```
thermohaline_coeff = 0
```

### thermohaline_option

determines which method to use for calculating thermohaline diffusion coef:

`'Kippenhahn'`

: use method of Kippenhahn, R., Ruschenplatt, G., & Thomas, H.-C. 1980, A&A, 91, 175.`'Traxler_Garaud_Stellmach_11'`

: use method of Traxler, Garaud, & Stellmach, ApJ Letters, 728:L29 (2011).`'Brown_Garaud_Stellmach_13'`

: use method of Brown, Garaud, & Stellmach, ApJ 768:34 (2013) Recommends`thermohaline_coeff = 1`

, but it can nevertheless be changed.

```
thermohaline_option = 'Kippenhahn'
```

### alt_scale_height_flag

If false, then stick to the usual definition – P/(g*rho).
If true, use min of the usual and sound speed * hydro time scale, sqrt(P/G)/rho.
Note that the ‘TDC’ `MLT_option`

does not respect the `alt_scale_height`

option, and continues to use `h = P / rho g`

even if that flag is set.

```
alt_scale_height_flag = .true.
```

### mlt_use_rotation_correction

When doing rotation, multiply `grad_rad`

by `ft_rot/ft_rot`

if this flag is true.

```
mlt_use_rotation_correction = .true.
```

### mlt_Pturb_factor

include MLT turbulent pressure at face k = mlt_Pturb_factor*0.5*(rho(k) + rho(k-1))*mlt_vc(k)**2/3 MLT turbulent pressure for cell k = avg of values at faces.

this replaces conv_dP_term_factor. also see extra_pressure vector and other_pressure routine

```
mlt_Pturb_factor = 0d0
```

### MLT_option

Options are:

‘none’ : just give radiative values with no mixing.

‘TDC’ : Time-dependent convection based on the Khufuss 1986 model. Reduces to Cox at long times.

‘Cox’ : MLT as developed in Cox & Giuli 1968, Chapter 14.

‘ML1’ : Bohm-Vitense 1958

‘ML2’ : Bohm and Cassinelli 1971

‘Mihalas’ : Mihalas 1978, Kurucz 1979

‘Henyey’ : Henyey, Vardya, and Bodenheimer 1965

The ‘Cox’ and ‘TDC’ options assumes optically thick material.
The other options are various ways of extending to include optically thin material.
Note that TDC does not respect the `alt_scale_height`

option, and continues to use `h = P / rho g`

even if that flag is set.

```
MLT_option = 'TDC'
```

### TDC options

`alpha_TDC_DAMP`

: The turbulent viscous damping parameter which determines the saturation of TDC. Increasing this decreases convection speeds.`alpha_TDC_DAMPR`

: The radiative damping parameter which determines the saturation of TDC. Increasing this decreases convection speeds.`alpha_TDC_PtdVdt`

: The prefactor on the term accounting for work done against turbulent pressure (P_turb * dV/dt). Physically this should be unity.`steps_before_use_TDC`

: TDC often struggles with models on the pre-main-sequence. Set this option to pick MLT_option=’Cox’ for the first several steps to get past the pre-MS. Note that if this option is positive then only either TDC or Cox will be used (depending on model number). THIS OVERRIDES MLT_option!

```
alpha_TDC_DAMP = 1d0
alpha_TDC_DAMPR = 0d0
alpha_TDC_PtdVdt = 0d0
steps_before_use_TDC = 0
```

### Henyey_MLT_y_param

### Henyey_MLT_nu_param

Values of the f1..f4 coefficients are taken from Table 1 of Ludwig et al. 1999, A&A, 346, 111
with the following exception: their value of f3 for Henyey convection is `f4/8`

when it should be
`8*f4`

, i.e., `f3=32*pi**2/3`

and `f4=4*pi**2/3`

. f3 and f4 are related to the henyey y parameter, so
for the ‘Henyey’ case they are set based on the value of `Henyey_y_param`

.

```
Henyey_MLT_y_param = 0.33333333d0
Henyey_MLT_nu_param = 8
```

### make_gradr_sticky_in_solver_iters

### min_logT_for_make_gradr_sticky_in_solver_iters

if true, then location that becomes radiative during solver iterations, stays radiative for rest of the solver iterations. to avoid flip-flopping between radiative and convective. also do this if max logT >= min_logT_for_make_gradr_sticky_in_solver_iters

```
make_gradr_sticky_in_solver_iters = .false.
min_logT_for_make_gradr_sticky_in_solver_iters = 1d99
```

### no_MLT_below_shock

if true, then no MLT below an outward going shock (just radiative).

```
no_MLT_below_shock = .false.
```

### mlt_make_surface_no_mixing

```
mlt_make_surface_no_mixing = .false.
```

### T_mix_limit

If there is any convection in surface zones with `T < T_mix_limit`

,
then extend the innermost such convective region outward all the way to the surface.
For example,

`T_mix_limit <= 0`

means omit this operation.`T_mix_limit = 1d5`

will effectively make the star convective down to the He++ region.

units in Kelvin

```
T_mix_limit = 0
```

### mlt_gradT_fraction

let f := `mlt_gradT_fraction`

if f is >= 0 and <= 1, then
gradT from mlt is replaced by `f*grada_at_face(k) + (1-f)*gradr(k)`

see also the vector control `adjust_mlt_gradT_fraction`

for fine grain control

```
mlt_gradT_fraction = -1
```

### okay_to_reduce_gradT_excess

`gradT_excess`

= `gradT_sub_grada`

= superadiabaticity.

Inefficient convection => large gradT excess and steep T gradient to enhance radiative transport.
Reduce gradT excess by making gradT closer to adiabatic gradient.
If true, code is allowed to adjust gradT to boost efficiency of energy transport
See `gradT_excess_f1`

, `gradT_excess_f2`

, and `gradT_excess_age_fraction`

below.

This is the treatment of convection, referred to as MLT++ in Section 7.2 of Paxton et al. (2013), that reduces the superadiabaticity in some radiation-dominated convective regions.

```
okay_to_reduce_gradT_excess = .false.
```

### gradT_excess_f1

### gradT_excess_f2

These are for calculation of efficiency boosted gradT.

```
gradT_excess_f1 = 1d-4
gradT_excess_f2 = 1d-3
```

### gradT_excess_age_fraction

These are for calculation of efficiency boosted gradT. Fraction of old to mix with new to get next.

```
gradT_excess_age_fraction = 0.9d0
```

### gradT_excess_max_change

These are for calculation of efficiency boosted gradT.
Maximum change allowed in one timestep for `gradT_excess_alpha`

.
Ignored if negative.

```
gradT_excess_max_change = -1d0
```

### gradT_excess_lambda1

### gradT_excess_beta1

In some situations you might want to force alfa = 1.
You can do that by setting `gradT_excess_lambda1 < 0`

.
The following are for the normal calculation of `gradT_excess_alfa`

```
gradT_excess_lambda1 = 1.0d0
gradT_excess_beta1 = 0.35d0
```

### gradT_excess_lambda2

### gradT_excess_beta2

The following are for the normal calculation of `gradT_excess_alfa`

.

```
gradT_excess_lambda2 = 0.5d0
gradT_excess_beta2 = 0.25d0
```

### gradT_excess_dlambda

### gradT_excess_dbeta

The following are for the normal calculation of `gradT_excess_alfa`

.

```
gradT_excess_dlambda = 0.1d0
gradT_excess_dbeta = 0.1d0
```

### gradT_excess_max_center_h1

No boost if center H1 > this limit.

```
gradT_excess_max_center_h1 = 1d0
```

### gradT_excess_min_center_he4

No boost if center He4 < this limit.

```
gradT_excess_min_center_he4 = 0d0
```

### gradT_excess_max_logT

No local boost if local logT > this limit.

```
gradT_excess_max_logT = 8
```

### gradT_excess_min_log_tau_full_on

### gradT_excess_max_log_tau_full_off

No local boost if local `log_tau < gradT_excess_max_log_tau_full_off`

.
Reduced local boost if local `log_tau < gradT_excess_min_log_tau_full_on`

.

```
gradT_excess_min_log_tau_full_on = -99
gradT_excess_max_log_tau_full_off = -99
```

### max_logT_for_mlt

No mlt at cell if local logT > this limit.

max_logT_for_mlt = 99

### use_superad_reduction

### superad_reduction_Gamma_limit

### superad_reduction_Gamma_limit_scale

### superad_reduction_Gamma_inv_scale

### superad_reduction_diff_grads_limit

### superad_reduction_limit

Implicit alternative to okay_to_reduce_gradT_excess

```
use_superad_reduction = .false.
superad_reduction_Gamma_limit = 0.5d0
superad_reduction_Gamma_limit_scale = 5d0
superad_reduction_Gamma_inv_scale = 5d0
superad_reduction_diff_grads_limit = 1d-3
superad_reduction_limit = -1d0
```

#### overshooting

There are two schemes implemented in MESA to treat overshooting: a step overshoot scheme and an exponential scheme.

Parameters for exponential diffusive overshoot are described in the paper by Falk Herwig, “The evolution of AGB stars with convective overshoot”, A&A, 360, 952-968 (2000).

Overshooting depends on the classification of the convective zone and can be different at the top and the bottom of the zone.

The overshooting controls are based on convection-zone and convection-boundary matching criteria.
These criteria are `overshoot_zone_type`

, `overshoot_zone_loc`

and `overshoot_bdy_loc`

.
The overshooting parameter values corresponding to the first set of matching criteria will be used.
Therefore, narrower criteria should precede more general ones (i.e have lower array indices).

These are arrays of size `NUM_OVERSHOOT_PARAM_SETS`

which is defined in
`star_data/public/star_data_def.inc`

(currently 16)

```
overshoot_scheme(:) = '' ! ``exponential``, ``step``, ``other``
overshoot_zone_type(:) = '' ! ``burn_H``, ``burn_He``, ``burn_Z``, ``nonburn``, ``any``
overshoot_zone_loc(:) = '' ! ``core``, ``shell``, ``any``
overshoot_bdy_loc(:) = '' ! ``bottom``, ``top``, ``any``
```

Amount of overshooting from edge of convective zone
These are arrays of size `NUM_OVERSHOOT_PARAM_SETS`

which is defined in
`star_data/public/star_data_def.inc`

(currently 16)

```
overshoot_f(:) = 0d0
overshoot_f0(:) = 0d0
```

The switch from convective mixing to overshooting happens at a distance f0*Hp into the convection zone
from the estimated location where `grad_ad = grad_rad`

, where Hp is the pressure scale height at that location.
A value <= 0 for f0 is a mistake – you are required to set f0 as well as f.
take a look at the following from an email concerning this:
Overshooting works by taking the diffusion mixing coefficient at the edge
of the convection zone and extending it beyond the zone. But – and here’s the issue –
at the exact edge of the zone the mixing coefficient goes to 0. So we don’t want that.
Instead we want the value of the mixing coeff NEAR the edge, but not AT the edge.
The “f0” parameter determines the exact meaning of “near” for this. It tells the code
how far back into the zone to go in terms of scale height. The overshooting actually
begins at the location determined by f0 back into the convection zone rather than at
the edge where the diffusion coeff is ill-defined. So, for example, if you want
overshooting of 0.2 scale heights beyond the normal edge, you might want to back up
0.05 scale heights to get the diffusion coeff from near the edge and then go out
by 0.25 scale heights from there to reach 0.2 Hp beyond the old boundary. In the
inlist this would mean setting the “f0” to 0.05 and the “f” to 0.25.

For step overshoot: overshooting extends a distance overshoot_f*Hp0 from r0 with constant diffusion coefficient
D = overshoot_D0 + overshoot_Delta0*D_ob
where D_ob is the convective diffusivity at the bottom (top) of the step overshoot region for outward (inward) overshooting.
These are arrays of size `NUM_OVERSHOOT_PARAM_SETS`

which is defined in
`star_data/public/star_data_def.inc`

(currently 16)

```
overshoot_D0(:) = 0d0
overshoot_Delta0(:) = 1d0
```

You can specify a range of star masses over which overshooting
above H burning zones is gradually enabled.
Do specified overshooting above H burning zone if `star_mass`

>= this (Msun).
These are arrays of size `NUM_OVERSHOOT_PARAM_SETS`

which is defined in
`star_data/public/star_data_def.inc`

(currently 16)

```
overshoot_mass_full_on(:) = 0d0
```

You can specify a range of star masses over which overshooting
above H burning zones is gradually enabled.
No overshooting above H burning zone if `star_mass`

<= this (Msun).
These are arrays of size `NUM_OVERSHOOT_PARAM_SETS`

which is defined in
`star_data/public/star_data_def.inc`

(currently 16)

```
overshoot_mass_full_off(:) = 0d0
```

### overshoot_D_min

Overshooting shuts off when the exponential decay has dropped the diffusion coefficient to this level.

```
overshoot_D_min = 1d2
```

### overshoot_brunt_B_max

Terminate overshoot region when encounter stabilizing composition gradient
where (unsmoothed) `brunt_B`

is greater than this limit. (<= 0 means ignore this limit)
note: both `brunt_B`

and `gradL_composition_term`

come from `unsmoothed_brunt_B`

and differ only in optional smoothing.
(see `num_cells_for_smooth_brunt_B`

and `num_cells_for_smooth_gradL_composition_term`

).

```
overshoot_brunt_B_max = 0d0
```

### min_overshoot_q

Overshooting is only allowed at locations with mass `m >= min_overshoot_q * mstar`

.
E.g., if `min_overshoot_q = 0.1`

, then only the outer 90% by mass can have overshooting.
This provides a simple way of suppressing bogus center overshooting in which a small
convective region at the core can produce excessively large overshooting because of
a large pressure scale height at the center.

```
min_overshoot_q = 0d0
```

NOTE: In addition to giving these ‘f’ parameters non-zero values, you should also
check the settings for `mass_for_overshoot_full_on`

and `mass_for_overshoot_full_off`

.

### overshoot_alpha

The value of Hp for overshooting is limited to the radial thickness
of the convection zone divided by `overshoot_alpha`

.
only used when > 0. if <= 0, then use `mixing_length_alpha`

instead.

```
overshoot_alpha = -1
```

### limit_overshoot_Hp_using_size_of_convection_zone

if false, allow large distance of overshoot for small convective zones.

```
limit_overshoot_Hp_using_size_of_convection_zone = .true.
```

### burn_z_mix_region_logT

### burn_he_mix_region_logT

### burn_h_mix_region_logT

max logT in convective region determines burn type for overshooting

```
burn_z_mix_region_logT = 8.7d0
burn_he_mix_region_logT = 7.7d0
burn_h_mix_region_logT = 6.7d0
```

### max_Y_for_burn_z_mix_region

### max_X_for_burn_he_mix_region

Even if a region reaches the above temperature to be considered as a z_burn region, only set it as such if the helium mass fraction in all points of the region is below max_Y_for_burn_z_mix_region. Similarly, max_X_for_burn_he_mix_region controls if a region is considered as a he_burn region in terms of the hydrogen mass fraction.

```
max_Y_for_burn_z_mix_region = 1d-4
max_X_for_burn_he_mix_region = 1d-4
```

#### Predictive mixing

Predictive mixing is an approach for expanding convective boundaries until gradr = grada on the convective side of the boundary (as required by the criterion that the convective velocity and luminosity vanish at the boundary). It is discussed in detail in Paxton et al. 2018, ApJ, in press: “Modules for Experiments in Stellar Astrophysics (MESA): Convective boundaries, element diffusion, and massive star explosions”

Predictive mixing is controlled by specifying a set of parameters, which combines matching
criteria (determining which boundaries to apply the predictive mixing to) together with
values (determining how the predictive mixing should operate at those boundaries). Up to
`NUM_PREDICTIVE_PARAM_SETS`

of these parameter sets can be defined (see `star_def.inc`

for value).

### predictive_mix

Set to .true. to enable this set of parameters

```
predictive_mix(1) = .false.
```

### predictive_zone_type

Matching criterion for the type of the convection zone. Possible values are `burn_H`

(hydrogen burning), `burn_He`

(helium burning), `burn_Z`

(metal burning), `nonburn`

(no burning) or `any`

(which matches any type of zone).

```
predictive_zone_type(1) = ''
```

### predictive_zone_loc

Matching criterion for the location of the convection zone. Possible values are `core`

(the core convection zone), `shell`

(a convective shell), `surf`

(the surface convection
zone) or `any`

(which matches any location).

```
predictive_zone_loc(1) = ''
```

### predictive_bdy_loc

Matching criterion for the location of the convective boundary. Possible values are
`top`

(the top of the convection zone), `bottom`

(the bottom of the convection zone)
or `any`

(which matches any location).

```
predictive_bdy_loc(1) = ''
```

### predictive_bdy_q_min

Matching criterion for the minimum fractional mass coordinate of the convective boundary

```
predictive_bdy_q_min(1) = 0d0
```

### predictive_bdy_q_max

Matching criterion for the maximum fractional mass coordinate of the convective boundary

```
predictive_bdy_q_max(1) = 1d0
```

### predictive_superad_thresh

Threshold for minimum superadiabaticity in the predictive mixing scheme; boundary expansion stops when gradr/grada-1 drops below this threshold. Default value is usually good for main-sequence evolution; for core He-burning, set to 0.005, 0.01 or larger to prevent splitting of the core convection zone and/or core breathing pulses.

```
predictive_superad_thresh(1) = 0d0
```

### predictive_avoid_reversal

Species to monitor for reversals in abundance evolution. If this is set to the name of a species, then the predictive mixing scheme will try to avoid causing reversals in the abundance of that species (e.g., changing the abundance evolution from decreasing to increasing). Set to ‘he4’ during core He-burning to prevent splitting of the core convection zone and/or core breathing pulses.

```
predictive_avoid_reversal(1) = ''
```

### predictive_limit_ingestion

### predictive_ingestion_factor

Limit the rate of ingestion of a species, following the prescription given in
equation (2) of Constantino, Campbell & Lattanzio (2017, MNRAS, 472, 4900). The control
`predictive_limit_ingestion`

specifies which species to limit, and the control
`predictive_ingestion_factor`

gives the multiplying factor. Setting this factor to 5/12
is the same as choosing alpha_i = 1 in their equation (2).

```
predictive_limit_ingestion(1) = ''
predictive_ingestion_factor(1) = 0d0
```

#### Convective premixing

Convective premixing is a approach to handling mixing in convection zones that improves upon the predictive mixing scheme described above. Like predictive mixing, it expands convective boundaries until gradr = grada on the convective side of the boundary. Unlike predictive mixing, it directly modifies abundances in the stellar model, via a iterative series of mixings-to-homogeneity over a shifting window of cells. This iterative approach allows convective premixing to build ‘classical’ semiconvection regions, where the abundance gradient is tuned to yield convective neutrality.

NOTE: the history columns that give info on the convective and semi convective boundaries
(i.e., `mass_conv_core`

and `mass_semiconv_core`

) do not work with CPM.
Instead, one should look at the profiles to see where the boundaries are.

### do_conv_premix

Set to .true. to perform convective premixing. Note that this cannot be enabled at the
same time as the `predictive_mix`

control

```
do_conv_premix = .false.
```

### do_premix_heating

if true, calculate heating term associated with changes in internal energy due to any abundance changes from convective premixing, and include this term in the energy equation.

```
do_premix_heating = .true.
```

### conv_premix_avoid_increase

Attempt to avoid increases in the abundance of species being burned. Sometimes, the
convective premixing scheme can cause the abundance of a species being burned (e.g.,
helium during core helium burning) to increase across a timestep. This typically arises
when the scheme mixes a fresh supply of the species into the convection zone where the
burning is occurring. Setting the `conv_premix_avoid_increase`

control to .true. will
tell the scheme to avoid such outcomes, if possible. In the case of core helium burning,
this helps to reduces the incidences of core breathing pulses (although in some situations
it doesn’t completely eliminate them).

```
conv_premix_avoid_increase = .false.
```

### conv_premix_time_factor

Scaling factor for deciding whether a convective boundary has enough time to advance during a timestep. Simple physical arguments suggest that a convective boundary requires a time delta_t ~ delta_r/v_conv to advance a distance delta_r. The convective premixing algorithm keeps a tally of how much time a boundary has spent advancing, and it prevents further advancing if this time would exceed conv_premix_time_factor*dt, where dt is the current timestep. Setting conv_premix_time_factor to a value <= 0 disables this check. STILL UNDER DEVELOPMENT, AND DISABLED BY DEFAULT

```
conv_premix_time_factor = 0.0
```

### conv_premix_fix_pgas

Flag to decide whether gas pressure is kept constant during premixing (.true.), or instead density is kept constant (.false.). In both cases, temperature is kept constant.

```
conv_premix_fix_pgas = .true.
```

### conv_premix_dump_snapshots

Flag to write out snapshots of the intermediate stages during the convective premixing iterations.
Refer to the `dump_snapshot_`

routine in star/private/conv_premix.f90 to see what’s written out. Note
that this can quickly fill up your disk!

```
conv_premix_dump_snapshots = .false.
```

#### Rayleigh Taylor Instability

derived from Paul Duffell’s code RT1D.

### RTI_smooth_mass

### RTI_smooth_iterations

### RTI_smooth_fraction

smoothing for `dPdr_dRhodr_info`

done at start of step

```
RTI_smooth_mass = 0d0
RTI_smooth_iterations = 0
RTI_smooth_fraction = 1d0
```

### alpha_RTI_diffusion_factor

### dudt_RTI_diffusion_factor

### dedt_RTI_diffusion_factor

### dlnddt_RTI_diffusion_factor

### composition_RTI_diffusion_factor

### max_M_RTI_factors_full_on

### min_M_RTI_factors_full_off

```
alpha_RTI_diffusion_factor = 1d0
dudt_RTI_diffusion_factor = 1d0
dedt_RTI_diffusion_factor = 1d0
dlnddt_RTI_diffusion_factor = 1d0
composition_RTI_diffusion_factor = 1d0
max_M_RTI_factors_full_on = 1d99
min_M_RTI_factors_full_off = 1d99
```

### alpha_RTI_src_max_q

### alpha_RTI_src_min_q

option to set `alpha_RTI`

source term to zero when cell q out of bounds.
to turn off RTI near surface or center

```
alpha_RTI_src_max_q = 1d0
alpha_RTI_src_min_q = 0d0
```

### alpha_RTI_src_min_v_div_cs

option to set alpha_RTI source term to zero when v/cs < this min. e.g. to filter out false sources ahead of shock

```
alpha_RTI_src_min_v_div_cs = 1d0
```

### Radial Stellar Pulsations (RSP)

inspired by Radec Smolec’s Program

must set mass, Teff, L, X, and Z.

```
RSP_mass = -1
RSP_Teff = -1
RSP_L = -1
RSP_X = -1
RSP_Z = -1
```

Parameters of the convection model.
Note that `RSP_alfap`

, `RSP_alfas`

, `RSP_alfac`

, `RSP_alfad`

and `RSP_gammar`

are expressed in the units of standard values.
Standard values are the ones for which static version of the Kuhfuss
model reduces to standard MLT. See Table 1 in Smolec & Moskalik (2008)
for standard values and the description of the parameters.

```
RSP_alfa = 1.5d0 ! mixing length; alfa = 0 gives a purely radiative model.
RSP_alfac = 1.0d0 ! convective flux; Lc ~ RSP_alfac
RSP_alfas = 1.0d0 ! turbulent source; Lc ~ 1/ALFAS; PII ~ RSP_alfas
RSP_alfad = 1.0d0 ! turbulent dissipation; damp ~ RSP_alfad
RSP_alfap = 0.0d0 ! turbulent pressure; Pt ~ alfap
RSP_alfat = 0.0d0 ! turbulent flux; Lt ~ RSP_alfat; overshooting.
RSP_alfam = 0.25d0 ! eddy viscosity; Chi & Eq ~ RSP_alfam
RSP_gammar = 0.0d0 ! radiative losses; dampR ~ RSP_gammar
```

time weighting for end-of-step vs start-of-step values in equations. 1 corresponds to fully implicit scheme - stable, but can have large numerical damping. 0.5 corresponds to trapezoidal rule integration - gives least numerical damping. do not use values less than 0.5. strongly recommend 0.5 for theta and thetat. don’t mess with any of these unless you know what you are doing or like to watch the code crash.

```
RSP_theta = 0.5d0 ! Pgas and Prad
RSP_thetat = 0.5d0 ! Pturb
RSP_thetae = 0.5d0 ! erad in terms using f_Edd
RSP_thetaq = 1.0d0 ! Pvsc
RSP_thetau = 1.0d0 ! Eq and Uq
RSP_wtr = 0.6667d0 ! Lr
RSP_wtc = 0.6667d0 ! Lc
RSP_wtt = 0.6667d0 ! Lt
RSP_gam = 1.0d0 ! Et src_snk
```

controls for building the initial model

```
RSP_nz = 150
RSP_nz_outer = 40
RSP_T_anchor = 11d3
RSP_T_inner = 2d6
RSP_testing = .false.
```

```
RSP_dq_1_factor = 2d0
RSP_max_outer_dm_tries = 100
RSP_max_inner_scale_tries = 100
RSP_T_anchor_tolerance = 1d-8
```

allowed relative difference between T at base of outer region and T_anchor if fail trying to create initial model, try increasing this to 1d-6 or more

```
RSP_T_inner_tolerance = 1d-8
```

allowed relative difference between T at inner boundary and T_inner if fail trying to create initial model, try increasing this to 1d-6 or more

```
RSP_relax_initial_model = .true.
RSP_relax_alfap_before_alfat = .true.
RSP_relax_max_tries = 1000
RSP_relax_dm_tolerance = 1d-6
```

Initial kick makes use of the scaled linear velocity eigenvector of a given mode or of the linear combination of the eigenvectors for the fundamental mode and first two radial overtones. The surface velocity is set to RSP_kick_vsurf_km_per_sec and the mode content is set by RSP_fraction_1st_overtone and RSP_fraction_2nd_overtone

```
RSP_kick_vsurf_km_per_sec = 0.1d0
RSP_fraction_1st_overtone = 0d0
RSP_fraction_2nd_overtone = 0d0
```

fraction from fundamental = 1d0 - (1st + 2nd) Note: This is important for models in which two or more modes are linearly unstable. Appropriate setting may help to arrive at the desired mode, since the final pulsation state may depend on initial conditions set by the three parameters above. Integration of the same model with different initial kicks is a way to study the nonlinear mode selection - for an example see Fig. 1 in Smolec & Moskalik (2010).

random initial velocity profile. added to any kick from eigenvector.

```
RSP_Avel = 0d0
RSP_Arnd = 0d0
```

period controls

```
RSP_target_steps_per_cycle = 600
RSP_min_max_R_for_periods = -1
RSP_min_deltaR_for_periods = -1
RSP_min_PERIOD_div_PERIODLIN = 0.5d0
RSP_mode_for_setting_PERIODLIN = 1
RSP_default_PERIODLIN = 34560
```

when to stop

```
RSP_max_num_periods = -1
RSP_GREKM_avg_abs_frac_new = 0.1d0
RSP_GREKM_avg_abs_limit = -1
```

timestep limiting

```
RSP_initial_dt_factor = 1d-2
```

start with smaller timestep to give time for initial model to adjust

```
RSP_v_div_cs_threshold_for_dt_limit = 0.8d0
RSP_max_dt_times_min_dr_div_cs = 2d0
```

i.e., make dt <= this times min sound crossing time dr/cs only considering cells with abs(v)/cs > threshold

```
RSP_max_dt_times_min_rad_diff_time = -1d0
```

make dt <= min time for radiative diffusion for RHD

```
RSP_max_dt = -1
RSP_report_limit_dt = .false.
```

artificial viscosity controls for the equations see: Appendix C in Stellingwerf (1975). In principle, for not too-non-adiabatic convective models artificial viscosity is not needed or should be very small. Hence a large cut-off parameter below (in purely radiative models the default value for cut-off was 0.01)

```
RSP_cq = 4.0d0
RSP_zsh = 0.1d0
```

zsh > 0 delays onset of artificial viscosity can eliminate most/all interior dissipation while still providing for extreme cases. using this parameter the dependence of limiting amplitude on cq is very weak. for Tscharnuter & Winkler form of artificial viscosity

```
RSP_Qvisc_linear = 0d0
RSP_Qvisc_quadratic = 0d0
```

as described in section 4.2 of mesa3, 2015. RSP_Qvisc_linear is analogous to shock_spread_linear RSP_Qvisc_quadratic is analogous to shock_spread_quadratic if switch to this form, set RSP_cq = 0 to shut off the Neumann & Richtmyer form. note that this form also uses RSP_zsh to delay onset of artificial viscosity

surface pressure. provides outer boundary condition for momentum equation.

```
RSP_use_Prad_for_Psurf = .false.
RSP_use_atm_grey_with_kap_for_Psurf = .false.
RSP_tau_surf_for_atm_grey_with_kap = 3d-3
RSP_fixed_Psurf = .true.
RSP_Psurf = 0d0
set_RSP_Psurf_to_multiple_of_initial_P1 = -1
```

set RSP_Psurf to this times initial surface cell pressure

```
RSP_surface_tau = 0.001d0
```

solver controls

```
RSP_tol_max_corr = 1d-8
RSP_tol_max_resid = 1d-6
RSP_max_iters_per_try = 100
RSP_max_retries_per_step = 50
RSP_report_undercorrections = .false.
RSP_nz_div_IBOTOM = 30d0
RSP_min_tau_for_turbulent_flux = 2d2
```

output data for work integrals during a particular period

```
RSP_work_period = -1
RSP_work_filename = 'work.data'
```

output data for 3d map. format same as for gnuplot pm3d

```
RSP_write_map = .false.
RSP_map_columns_filename = 'map_columns.list'
```

items listed in your map columns must also appear in your profile columns

```
RSP_map_filename = 'map.data'
RSP_map_first_period = -1
RSP_map_last_period = -1
RSP_map_zone_interval = 2
RSP_map_history_filename = 'map_history.data'
```

rsp hooks

```
use_other_RSP_linear_analysis = .false.
use_other_RSP_build_model = .false.
```

for special tests can set ALFA = 0 for pure radiative with no turbulence or convection. can set zero_gravity = .true. can set opacity to be constant times density.

```
RSP_kap_density_factor = -1
```

else set opacity to this times density

rsp misc

```
RSP_efl0 = 1.0d2
RSP_nmodes = 3
RSP_trace_RSP_build_model = .false.
```

```
use_RSP_new_start_scheme = .false.
```

```
RSP_Qvisc_linear_static = 0d0
```

```
RSP_relax_adjust_inner_mass_distribution = .true.
```

```
RSP_do_check_omega = .true.
```

```
RSP_report_check_omega_changes = .false.
```

```
RSP_hydro_only = .false.
```

this does not work with the standard build model, so requires use_other_RSP_build_model

#### mixing misc

such as smoothing and editing of diffusion coefficients

### mix_factor

Mixing coefficients are multiplied by this factor.
The `mix_factor`

is applied in subroutine `get_convection_sigmas`

in `star/private/mix_info.f90`

–
the lagrangian diffusion coefficient sigma(k) at cell boundary k is set to
`mix_factor*D*(4*pi*r(k)^2*rho_face(k))^2`

.
Note that the value of D is not changed – it is just used as a term in calculating sigma.

```
mix_factor = 1
```

### max_conv_vel_div_csound

convective velocities are limited to local sound speed times this factor

```
max_conv_vel_div_csound = 1d99
```

### max_v_for_convection

disable convection for locations with v > than this limit. In km/s.

```
max_v_for_convection = 1d99
```

### max_q_for_convection_with_hydro_on

disable convection for locations with q > than this limit when either v_flag or u_flag are true.

```
max_q_for_convection_with_hydro_on = 1d99
```

### max_v_div_cs_for_convection

disable convection for locations with abs(v)/cs > this limit

```
max_v_div_cs_for_convection = 1d99
```

### max_abs_du_div_cs_for_convection

main purpose is to force radiative in shock face

```
max_abs_du_div_cs_for_convection = 0.03d0
```

### prune_bad_cz_min_Hp_height

Lower limit on radial extent of cz (<= 0 to disable).
In units of average pressure scale height at top and bottom of region.
Remove tiny convection zones unless have strong nuclear burning
This allows emergence of very small cz at site of he core flash, for example.
i.e., remove if `size < prune_bad_cz_min_Hp_height`

.and.
`max_log_eps < prune_bad_cz_min_log_eps_nuc`

.

```
prune_bad_cz_min_Hp_height = 0
```

### prune_bad_cz_min_log_eps_nuc

Lower limit on max log eps nuc in cz.
remove if `size < prune_bad_cz_min_Hp_height`

.and.
`max_log_eps < prune_bad_cz_min_log_eps_nuc`

.

```
prune_bad_cz_min_log_eps_nuc = -99
```

### redo_conv_for_dr_lt_mixing_length

Check for small convection zones with total height less than mixing length
and redo with reduced `mixing_length_alpha`

to make `mixing_length <= dr`

.

```
redo_conv_for_dr_lt_mixing_length = .false.
```

### smooth_convective_bdy has been deleted.

### remove_mixing_glitches

If true, then okay to remove gaps and singletons.

```
remove_mixing_glitches = .true.
```

#### glitches

The following controls are for different kinds of “glitches” that can be removed.

### okay_to_remove_mixing_singleton

If true, remove singletons.

```
okay_to_remove_mixing_singleton = .true.
```

### clip_D_limit

Zero mixing diffusion coeffs that are smaller than this.

```
clip_D_limit = 0
```

### min_convective_gap

Close gap between convective regions if smaller than this (< 0 means skip this). Gap measured radially in units of pressure scale height.

```
min_convective_gap = -1
```

### min_thermohaline_gap

Close gap between thermohaline mixing regions if smaller than this (< 0 means skip this). Gap measured radially in units of pressure scale height.

```
min_thermohaline_gap = -1
```

### min_thermohaline_dropout

### max_dropout_gradL_sub_grada

If find radiative region embedded in thermohaline,
and `max(gradL - grada)`

in region is everywhere `< max_dropout_gradL_sub_grada`

and region height is `< min_thermohaline_dropout`

then convert the region to thermohaline.
`min_thermohaline_dropout <= 0`

disables.

```
min_thermohaline_dropout = -1
max_dropout_gradL_sub_grada = 1d-3
```

### min_semiconvection_gap

Close gap between semiconvective mixing regions if smaller than this (< 0 means skip this). Gap measured radially in units of pressure scale height.

```
min_semiconvection_gap = -1
```

### remove_embedded_semiconvection

If have a semiconvection region bounded on each side by convection, convert it to be convective too.

```
remove_embedded_semiconvection = .false.
```

### recalc_mix_info_after_evolve

Re-evaluate mixing info after each evolve step. This is helpful if you want the profiles to reflect the mixing params after the step; otherwise, they give the mixing info from the start of the step (i.e., one step out-of-date)

```
recalc_mix_info_after_evolve = .false.
```

### set_min_D_mix

### mass_lower_limit_for_min_D_mix

### mass_upper_limit_for_min_D_mix

### min_D_mix

`D_mix`

will be at least this large if `set_min_D_mix`

is true.
doesn’t apply for mass < lower limit or mass > upper limit.

```
set_min_D_mix = .false.
mass_lower_limit_for_min_D_mix = 0d0
mass_upper_limit_for_min_D_mix = 1d99
min_D_mix = 1d3
```

### set_min_D_mix_in_H_He

### min_D_mix_in_H_He

`D_mix`

will be at least this large in regions
where max mass fractions of H and He add to more that 0.5
if `set_min_D_mix_in_H_He`

is true.

```
set_min_D_mix_in_H_He = .false.
min_D_mix_in_H_He = 1d3
```

### set_min_D_mix_below_Tmax

### min_D_mix_below_Tmax

`D_mix`

will be at least this large for cells below location of max temperature
if `set_min_D_mix_below_Tmax`

is true.

```
set_min_D_mix_below_Tmax = .false.
min_D_mix_below_Tmax = 1d3
```

### min_center_Ye_for_min_D_mix

`min_D_mix`

is only used when `center_ye >= this`

i.e., when `center_ye`

drops below this, `min_D_mix = 0`

.

```
min_center_Ye_for_min_D_mix = 0.47d0
```

### smooth_outer_xa_big

### smooth_outer_xa_small

Soften composition jumps in outer layers.
If `smooth_outer_xa_big`

and `smooth_outer_xa_small`

are bigger than 0, then
starting from the outermost grid point, homogeneously mix a region of size
`smooth_outer_xa_small`

(in solar masses), and proceed inwards, linearly reducing
the size of the homogeneously mixed region in such a way that it becomes zero.
After going `smooth_outer_xa_big`

solar masses in. In this way, the outer `smooth_outer_xa_big`

solar masses are “cleaned” of composition jumps.

```
smooth_outer_xa_big = -1d0
smooth_outer_xa_small = -1d0
```

## rotation controls

In the following “am” stands for “angular momentum”.

the mesa implementation of rotation closely follows these papers:

Heger, Langer, & Woosley, ApJ, 528, 368. 2000

Heger, Woosley, & Spruit, ApJ, 626, 350. 2005

`D_DSI`

= dynamical shear instability`D_SH`

= Solberg-Hoiland`D_SSI`

= secular shear instability`D_ES`

= Eddington-Sweet circulation`D_GSF`

= Goldreich-Schubert-Fricke`D_ST`

= Spruit-Tayler dynamo

### skip_rotation_in_convection_zones

if true, then set rotational diffusion coefficients to 0 in convective regions. This applies both for material mixing and diffusion of angular momentum.

```
skip_rotation_in_convection_zones = .false.
```

### am_D_mix_factor

Rotation and mixing of material.
`D_mix`

= diffusion coefficient for mixing of material.
It is sum of non-rotational and rotational components.
The rotational part is multiplied by this factor.

```
D_mix = D_mix_non_rotation + f*am_D_mix_factor*(
D_DSI_factor * D_DSI +
D_SH_factor * D_SH +
D_SSI_factor * D_SSI +
D_ES_factor * D_ES +
D_GSF_factor * D_GSF +
D_ST_factor * D_ST)
```

```
f = 1 when logT <= D_mix_rotation_max_logT_full_on = full_on
= 0 when logT >= D_mix_rotation_min_logT_full_on = full_off
= (log(T)-full_on)/(full_off-full_on) else
```

note that for regions with brunt N^2 < 0, we set Richardson number to 1 which is > Ri_critical and therefore turns off DSI and SSI

according to Heger et al 2000 : 1/30d0 by default : 0

```
am_D_mix_factor = 0
```

### am_nu_factor

### am_nu_non_rotation_factor

diffusion of angular momentum

`am_nu`

= diffusion coefficient for angular momentum

```
am_nu_non_rot = am_nu_factor*am_nu_non_rotation_factor*D_mix_non_rotation
am_nu_rot = am_nu_factor*(
am_nu_visc_factor* D_visc +
am_nu_DSI_factor * D_DSI +
am_nu_SH_factor * D_SH +
am_nu_SSI_factor * D_SSI +
am_nu_ES_factor * D_ES +
am_nu_GSF_factor * D_GSF +
am_nu_ST_factor * nu_ST)
am_nu = am_nu_non_rot + am_nu_rot
```

Note that for regions with brunt N^2 < 0, we set Richardson number to 1 which is > Ri_critical and therefore turns off DSI and SSI.

see also `star_job`

controls for `am_nu_rot_flag`

```
am_nu_factor = 1
am_nu_non_rotation_factor = 1
```

### am_nu_DSI_factor

< 0 means use `D_DSI_factor`

```
am_nu_DSI_factor = -1
```

### am_nu_SSI_factor

< 0 means use `D_SSI_factor`

```
am_nu_SSI_factor = -1
```

### am_nu_SH_factor

< 0 means use `D_SH_factor`

```
am_nu_SH_factor = -1
```

### am_nu_ES_factor

< 0 means use `D_ES_factor`

```
am_nu_ES_factor = -1
```

### am_nu_GSF_factor

< 0 means use `D_GSF_factor`

```
am_nu_GSF_factor = -1
```

### am_nu_ST_factor

< 0 means use `D_ST_factor`

```
am_nu_ST_factor = -1
```

### am_nu_visc_factor

< 0 means use `D_visc_factor`

.
By default = 1 to mix angular momentum.

```
am_nu_visc_factor = 1
```

### am_nu_omega_rot_factor

### am_nu_omega_non_rot_factor

dj/dt = d/dm((4 pi r^2 rho)^2*(am_nu_omega*i_rot*domega/dm + am_nu_j*dj/dm)) am_nu_omega = am_nu_omega_non_rot_factor*am_nu_non_rot + am_nu_omega_rot_factor*am_nu_rot

```
am_nu_omega_rot_factor = 1
am_nu_omega_non_rot_factor = 1
```

### am_nu_j_rot_factor

### am_nu_j_non_rot_factor

dj/dt = d/dm((4 pi r^2 rho)^2*(am_nu_omega*i_rot*domega/dm + am_nu_j*dj/dm)) am_nu_j = am_nu_j_non_rot_factor*am_nu_non_rot + am_nu_j_rot_factor*am_nu_rot

```
am_nu_j_rot_factor = 0
am_nu_j_non_rot_factor = 0
```

### set_uniform_am_nu_non_rot

### uniform_am_nu_non_rot

You can specify a uniform value for `am_nu_non_rot`

by setting this flag true.
A large uniform `am_nu`

will produce a uniform omega.

```
set_uniform_am_nu_non_rot = .false.
uniform_am_nu_non_rot = 1d20
```

### set_min_am_nu_non_rot

### min_am_nu_non_rot

You can also specify a minimum `am_nu_non_rot`

.
`am_nu`

will be at least this large.

```
set_min_am_nu_non_rot = .false.
min_am_nu_non_rot = 1d8
```

### min_center_Ye_for_min_am_nu_non_rot

`min_am_nu_non_rot`

is only used when center Ye >= this.

```
min_center_Ye_for_min_am_nu_non_rot = 0.47d0
```

Each rotationally induced diffusion coefficient has a factor that lets you control it. Value of 1 gives normal strength; value of 0 turns it off.

Note that for regions with brunt N^2 < 0, we set Richardson number to 1, which is > Ri_critical and therefore turns off DSI and SSI.

```
D_DSI_factor = 0
D_SH_factor = 0
D_SSI_factor = 0
D_ES_factor = 0
D_GSF_factor = 0
D_ST_factor = 0
```

### D_visc_factor

Kinematic shear viscosity. Should be = 0 because viscosity doesn’t mix chemical elements.

```
D_visc_factor = 0
```

### am_gradmu_factor

Sensitivity to composition gradients.
In calculation of rotational induced mixing, `grad_mu`

is multiplied by `am_gradmu_factor`

.
Value from from Heger et al 2000.

```
am_gradmu_factor = 0.05d0
```

Spatial smoothing is used in calculations of diffusion coefficients. These control the smoothing window widths (number of cells on each side).

```
smooth_D_DSI = 0
smooth_D_SH = 0
smooth_D_SSI = 0
smooth_D_ES = 0
smooth_D_GSF = 0
smooth_D_ST = 0
smooth_nu_ST = 0
smooth_D_omega = 0
smooth_am_nu_rot = 0
```

### ST_angsmt

### ST_angsml

Temporal smoothing of ST coefficients. See rotation_mix_info.f90 for details

```
ST_angsmt = 0.2d0
ST_angsml = 1d-3
```

### simple_i_rot_flag

If true, `i_rot = (2/3)*r^2`

.
If false, use slightly more complex expression
that takes into account finite shell thickness.
In practice, there doesn’t seem to be a significant difference.

```
simple_i_rot_flag = .false.
```

### do_adjust_J_lost

### adjust_J_fraction

adjust angular momentum With do_adjust_J_lost = .false., the angular momentum removed via winds from the star corresponds to that contained in the removed layers. However, since j_rot can increase steeply in the very outer layers, very small steps are required to obtain a convergent solution. To avoid this, the do_adjust_J_lost option adjusts the angular momentum content of layers below those removed, such that

```
actual_J_lost = &
adjust_J_fraction*mass_lost*s% j_rot_surf + &
(1d0 - adjust_J_fraction)*s% angular_momentum_removed
```

where s% angular_momentum_removed is the angular momentum contained in the removed layers of the star in that step. Note that s% angular_momentum_removed is set to actual_J_lost after this.

The region from which angular momentum is removed is chosen such that at its bottom q<min_q_for_adjust_J_lost, it contains at least min_J_div_delta_J times the angular momentum that needs to be accounted for. Angular momentum in these regions is adjusted in such a way that no artificial shear is produced at the inner boundary.

This can also be used to model mass loss mechanisms that remove more angular momentum than mass_lost*s% j_rot_surf, for instance magnetic braking or wind mass loss. In that case, you can use the use_other_j_for_adjust_J_lost option to specify a specific angular momentum of removed material different from j_rot_surf

In order to prevent the algorithm from digging to deep to adjust J, there is a timestep limit adjust_J_q_limit

```
do_adjust_J_lost = .true.
adjust_J_fraction = 1d0
min_q_for_adjust_J_lost = 0.995d0
min_J_div_delta_J = 3d0
```

### premix_omega

if premix_omega is true, then do 1/2 of the transport of angular momentum before updating the structure and 1/2 after. otherwise, do all of the transport after updating the structure. RECOMMENDED to turn it on when modelling an accreting star or when using do_adjust_J_lost.

```
premix_omega = .true.
```

### angular_momentum_error_warn

### angular_momentum_error_stop

if the relative change in total angular momentum exceeds these values, then a warning is given on the terminal output, or the simulation is stopped altogether. Not applied when using other_torque routines or for binaries.

```
angular_momentum_error_warn = 5d-6
angular_momentum_error_retry = 1d-6
```

### recalc_mixing_info_each_substep

if `recalc_mixing_info_each_substep`

is true, then recalculate the omega mixing coefficients after each substep of the solve omega mix process.

```
recalc_mixing_info_each_substep = .false.
```

### w_div_wcrit_max

When fitted_fp_ft_i_rot = .true., limit fp and ft to their values at this w_div_wcrit

```
w_div_wcrit_max = 0.90d0
```

### w_div_wcrit_max2

When w_div_wc_flag is true, rather than a hard limit on w_div_wcrit we use w_div_wcrit_max2<w_div_wcrit_max to provide a smooth transition. In the limit of j_rot->infinity, the resulting w_div_wc will match w_div_wcrit_max, while nothing is done when w_div_wcrit_max<w_div_wcrit_max2

```
w_div_wcrit_max2 = 0.89d0
```

### FP_min

### FT_min

Lower limits for rotational distortion corrections factors FP and FT. Used for the calculation when fitted_fp_ft_i_rot = .false., otherwise the limits are set using w_div_wcrit_max

```
FP_min = 0.75d0
FT_min = 0.95d0
```

### FP_error_limit

If calculate an fp < this, treat it as an error. Used for the calculation when fitted_fp_ft_i_rot = .false.

```
FP_error_limit = 0d0
```

### FT_error_limit

If calculate an ft < this, treat it as an error. Used for the calculation when fitted_fp_ft_i_rot = .false.

```
FT_error_limit = 0d0
```

### D_mix_rotation_max_logT_full_on

Use rotational components of `D_mix`

for locations where logT <= this.
For numerical stability, turn off rotational part of `D_mix`

at very high T.

```
D_mix_rotation_max_logT_full_on = 9.4d0
```

### D_mix_rotation_min_logT_full_off

Drop rotational components of `D_mix`

for locations where logT >= this.
For numerical stability, turn off rotational part of `D_mix`

at very high T.

```
D_mix_rotation_min_logT_full_off = 9.5d0
```

### D_omega_max_replacement_fraction

### D_omega_growth_rate

### D_omega_mixing_rate

### D_omega_mixing_across_convection_boundary (previously called D_omega_mixing_in_convection_regions)

```
D_omega_mixing_rate = 1d0
D_omega_mixing_across_convection_boundary = .false.
max_q_for_D_omega_zero_in_convection_region = 0.8d0
```

### nu_omega_max_replacement_fraction

### nu_omega_growth_rate

### nu_omega_mixing_rate

### nu_omega_mixing_across_convection_boundary

```
nu_omega_mixing_rate = 1d0
nu_omega_mixing_across_convection_boundary = .false.
max_q_for_nu_omega_zero_in_convection_region = 0.8d0
```

## atmosphere boundary conditions

### atm_option

Controls how the surface temperature Tsurf and pressure Psurf are evaluated when setting up outer boundary conditions

`'T_tau'`

: set Tsurf and Psurf by solving for the atmosphere structure given a T(tau) relation. The choice of relation is set by the`atm_T_tau_relation`

control. See also the`atm_T_tau_opacity`

,`atm_T_tau_errtol`

,`atm_T_tau_max_tries`

and`atm_T_tau_max_steps`

controls.`'table'`

: set Tsurf and Psurf by interpolating in pre-calculated tables based on model atmospheres. The choice of table is set by the`atm_table`

control. Requires tau_factor = 1, as surface of the model must always attach at the base of the tables, so there is no flexibility to move model surface inward or outward. Note that tau_base = tau_surf is the location at which the model attaches to the table BCs, and there is no particular location identified as the photosphere, so we fall back to the surface values of L, R, and m to calculate quantities such as Teff and log_g. This is consistent with the assumptions used for table construction: geometrically thin atmospheres with constant flux.`'irradiated_grey'`

: set Tsurf by solving for the atmosphere structure given the irradiated-grey T(tau) relation of Guillot, T, and Havel, M., A&A 527, A20 (2011). See also the`atm_irradiated_opacity`

,`atm_irradiated_errtol`

,`atm_irradiated_T_eq`

,`atm_irradiated_T_eq`

,`atm_irradiated_kap_v`

,`atm_irradiated_kap_v_div_kap_th`

,`atm_irradiated_P_surf`

and`atm_irradiated_max_tries`

controls.

```
atm_option = 'T_tau'
```

### atm_off_table_option

If have selected `'table'`

for `atm_option`

, fallback to using
this if the args are off the table. Possible choices are `'T_tau'`

or blank (in which case the code will halt when it encounters an off-table
arg)

```
atm_off_table_option = 'T_tau'
```

### atm_fixed_Teff

Set this when using `atm_option = 'fixed_Teff'`

```
atm_fixed_Teff = 0
```

### atm_fixed_Tsurf

Set this when using `atm_option = 'fixed_Tsurf'`

```
atm_fixed_Tsurf = 0
```

### atm_fixed_Psurf

Set this when using `atm_option = 'fixed_Psurf'`

```
atm_fixed_Psurf = -1
```

### Pextra_factor

Parameter for extra pressure in surface boundary conditions.
Pressure at optical depth tau is calculated as `P = tau*g/kap*(1 + Pextra)`

Pextra takes into account nonzero radiation pressure at tau=0.
The equation for Pextra includes `Pextra_factor`

```
Pextra = Pextra_factor*(kap/tau)*(L/M)/(6d0*pi*clight*cgrav)
```

For certain situations such super eddington L,
you may need to increase Pextra to help convergence.
e.g. try `Pextra_factor = 2`

Note that `Pextra_factor`

is only applied when `atm_option`

= `'T_tau'`

and `atm_T_tau_opacity`

= `'fixed'`

or ‘`iterated'`

.

```
Pextra_factor = 1
```

### atm_T_tau_relation

The T(tau) relation to use when `atm_option`

= `'T_tau'`

`'Eddington'`

: use the grey Eddington T(tau) relation.`'solar_Hopf'`

: use a grey T(tau) relation with an approximate Hopf function tuned to solar data. See Paper II, Sec. A.5. Equivalent to the fit given by Sonoi et al. (2019, A&A, 621, 84) to the Vernazza et al. (1981) VAL-C model.`'Krishna_Swamy'`

: use the grey T(tau) relation described by K.S. Krishna-Swamy, ApJ 145, 174–194 (1966).`'Trampedach_solar'`

: use the analytic fit by Ball (2021, RNAAS 5, 7) to the Hopf function for the solar simulation by Trampedach et al. (2014, MNRAS 442, 805–820)

```
atm_T_tau_relation = 'Eddington'
```

### atm_T_tau_opacity

Controls how opacities are calculated throughout the atmosphere when
`atm_option`

= `'T_tau'`

`'fixed'`

: use a uniform opacity, fixed to the opacity of the outermost cell of the interior model`'iterated'`

: use a uniform opacity, iterated to be consistent with the final Tsurf and Psurf at the base of the atmosphere.`'varying'`

: use a varying opacity consistent with the local T and P throughout the atmosphere. Involves numerical integration of the hydrostatic equilibrium equation.

```
atm_T_tau_opacity = 'fixed'
```

### atm_T_tau_errtol

Error tolerance for iterations and integrations when
`atm_option`

= `'T_tau' and ``atm_T_tau_opacity`

= `'iterated'`

or
`'varying'`

.

```
atm_T_tau_errtol = 1d-7
```

### atm_T_tau_max_iters

Maximum number of iterations for the opacity when
`atm_option`

= `'T_tau' and ``atm_T_tau_opacity`

= `'iterated'`

.

```
atm_T_tau_max_iters = 50
```

### atm_T_tau_max_steps

Maximum number of steps for integrating the hydrostatic equilibrium
equation when `atm_option`

= `'T_tau' and ``atm_T_tau_opacity`

= `'varying'`

.

```
atm_T_tau_max_steps = 500
```

### atm_table

Determines which table Tsurf and Psurf are interpolated in

`'tau_100'`

,`'tau_10'`

,`'tau_1'`

,`'tau_1m1'`

: use model atmosphere tables for Pgas and T at tau=100, 10, 1 or 0.1, respectively; solar Z only, as described in MESA Paper I (Paxton et al. 2011), Sec. 5.3. these tables are primarily for the evolution of low-mass stars, brown dwarfs, and giant planets. They are constructed from Castelli & Kurucz (2003) for Teff > 3000 K and the COND model atmospheres (Allard et al. 2001) for Teff < 3000 K. where no published results are available, the table has been filled in using integration of the Eddington T(tau) relation`'photosphere'`

: use model atmosphere tables for photosphere; range of Z’s, as described in MESA Paper I (Paxton et al. 2011), Sec. 5.3. the tables cover log(Z/Zsun) from -4 to 0.5 for a GN93 solar mixture, and span logg = -0.5 to 5.5 in steps of 0.5 dex and Teff = 2000 to 50 000 K in steps of 250 K. they are constructed, in order of precedence, using the PHOENIX model atmospheres (Hauschildt et al. 1999a,b) and the models by Castelli & Kurucz (2003). where neither is available, an entry is generated by integrating the Eddington T(tau) relation`'WD_tau_25'`

: hydrogen atmosphere tables for cool white dwarfs giving Pgas and T at log10(tau) = 1.4 (tau = 25.11886) Teff goes from 40,000 K down to 2,000K with step of 100 K Log10(g) goes from 9.5 down to 5.5 with step of 0.1. R.D. Rohrmann, L.G. Althaus, and S.O. Kepler, Lyman α wing absorption in cool white dwarf stars, Mon. Not. R. Astron. Soc. 411, 781–791 (2011)`'DB_WD_tau_25'`

: EXPERIMENTAL helium dominated (log(H/He)=-5.0) atmosphere tables for DB white dwarfs, provided by Odette Toloza and Detlev Koester. 5000K < Teff < 40000K

```
atm_table = 'tau_100'
```

### atm_irradiated_opacity

Controls how thermal opacities are calculated throughout the atmosphere when
`atm_option`

= `'irradiated_grey'`

`'fixed'`

: use a uniform opacity, fixed to the opacity of the outermost cell of the interior model.`'iterated'`

: use a uniform opacity, iterated to be consistent with the final Tsurf and Psurf at the base of the atmosphere.

```
atm_irradiated_opacity = 'fixed'
```

### atm_irradiated_errtol

Error tolerance for iterations when `atm_option`

= ```
'irradiated_grey'
and ``atm_irradiated_opacity
```

= `'iterated'`

.

```
atm_irradiated_errtol = 1d-7
```

### atm_irradiated_max_iters

Maximum number of iterations for the opacity when `atm_option`

=
`'irradiated_grey' and ``atm_irradiated_opacity`

= `'iterated'`

.

```
atm_irradiated_max_iters = 50
```

### atm_irradiated_T_eq

Equilibrium temperature based on irradiation.

```
irrad_flux = Lstar/(4*pi*orbit**2)
```

Area of planet in plane perpendicular to

`irrad_flux = pi*Rplanet**2`

.Stellar luminosity received by

`planet = irrad_flux*area`

.This luminosity determines

`T_eq`

:`T_eq**4 = irrad_flux/(4*sigma)`

.

```
atm_irradiated_T_eq = 100
```

### atm_irradiated_kap_v_div_kap_th

### atm_irradiated_kap_v

The T(tau) relation when `atm_option`

= `'irradiated_grey'`

depends on the
ratio `kap_v/kap_th`

where `kap_v`

is the planet atmosphere opacity for stellar
irradiation, and `kap_th`

is the thermal opacity for the internally produced
radiation. There are two ways to calculate the ratio:

if

`atm_irradiated_kap_v_div_kap_th`

> 0, then use it for`kap_v/kap_th`

if

`atm_irradiated_kap_v_div_kap_th`

== 0, then use`atm_irradiated_kap_v`

to set`kap_v`

, and then evaluate the ratio using`kap_th`

```
atm_irradiated_kap_v_div_kap_th = 0
atm_irradiated_kap_v = 4d-3
```

### atm_irradiated_P_surf

Surface pressure when `atm_option`

= `'irradiated_grey'`

;
default is 1 bar in cgs units.

```
atm_irradiated_P_surf = 1d6
```

### use_compression_outer_BC

gradient of compression vanishes at surface

see Grott, Chernigovski, Glatzel, 2005. d_dm(d_dm(r^2*v)) = 0 at surface by continuity, this is d_dm(d_dt(1/rho)) = 0 at surface finite volume form is (1/rho(1) - 1/rho_start(1)) = (1/rho(2) - 1/rho_start(2)) this BC determines the density for surface cell.

```
use_compression_outer_BC = .false.
```

### use_momentum_outer_BC

use `P_surf`

from atm to set pressure gradient at surface in momentum equation
calculate v(1) based on pressure difference `P_surf - P(1)`

```
use_momentum_outer_BC = .false.
```

### use_zero_Pgas_outer_BC

use `Psurf = Radiation_Pressure(T_start(1))`

```
use_zero_Pgas_outer_BC = .false.
```

### use_fixed_vsurf_outer_BC

### fixed_vsurf

v at outer boundary of model is set to be fixed_vsurf

```
use_fixed_vsurf_outer_BC = .false.
fixed_vsurf = 0
```

### use_fixed_Psurf_outer_BC

### fixed_Psurf

P at outer boundary of model is set to be fixed_Psurf

```
use_fixed_Psurf_outer_BC = .false.
fixed_Psurf = 0
```

### Tsurf_factor

used when `use_momentum_outer_BC`

`T_surf`

is set to `Tsurf_factor*T_black_body(L_surf,R_surf)`

```
Tsurf_factor = 1
```

### irradiation_flux

### column_depth_for_irradiation

```
irradiation_flux = 0
column_depth_for_irradiation = -1
```

### atm_build_tau_outer

### atm_build_dlogtau

### atm_build_errtol

Parameters controlling atmosphere structure building. MESA can
evaluate the spatial structure of the atmosphere for the
following `atm_option`

choice:

`'T_tau'`

The atmosphere structure data are appended to the interior model
when `add_atmosphere_to_pulsation = .true.`

. They do not affect
the surface boundary conditions applied to the interior model.

`atm_build_tau_outer`

specifies the outermost optical depth to
include in the atmosphere; `atm_build_dlntau`

specifies the
spacing of atmosphere points in (base-10) logarithmic optical depth;
and `atm_build_errtol`

specifies the error tolerance for evaluating
the structure.

```
atm_build_tau_outer = 1d-3
atm_build_dlogtau = 0.01
atm_build_errtol = 1d-8
```

### use_T_tau_gradr_factor

If `.true.`

, modify the radiative gradient so that the
temperature profile of the optically thin layers follow the
T(τ) relation chosen by `atm_T_tau_relation`

.

```
use_T_tau_gradr_factor = .false.
```

## mass gain or loss

### mass_change

Rate of accretion (Msun/year). Negative for mass loss.
This only applies when the `wind_scheme = ''`

.

```
mass_change = 0d0
```

### mdot_omega_power

Enhanced mass loss due to rotation as in Heger, Langer, and Woosley, 2000, ApJ, 528:368-396.

Mdot = Mdot_no_rotation/(1 - Osurf/Osurf_crit)^mdot_omega_power

where

Osurf = angular velocity at surface Osurf_crit^2 = (1 - Gamma_edd)*G*M/R^3 Gamma_edd = kappa*L/(4 pi c G M), Eddington factor

Typical value for `mdot_omega_power = 0.43`

.

Set to 0 to disable this feature.

```
mdot_omega_power = 0.43d0
```

### max_rotational_mdot_boost

This limits the rotational boost.

```
max_rotational_mdot_boost = 1d4
```

### max_mdot_jump_for_rotation

Don’t increase prev mdot by more that this.
NOTE: use `vcrit_max_years_for_timestep`

with this.

```
max_mdot_jump_for_rotation = 2
```

### lim_trace_rotational_mdot_boost

Output to terminal if boost > this.

```
lim_trace_rotational_mdot_boost = 1d99
```

### rotational_mdot_boost_fac

Increase mdot.

```
rotational_mdot_boost_fac = 1d5
```

### rotational_mdot_kh_fac

Kelvin-helmholtz boost.

```
rotational_mdot_kh_fac = 0.3d0
```

### surf_avg_tau_min

Use mass avg starting from this optical depth.

```
surf_avg_tau_min = 1
```

### surf_avg_tau

Use mass avg down to this optical depth.

```
surf_avg_tau = 100
```

### hot_wind_scheme

### hot_wind_Wolf_Rayet_scheme

### cool_wind_RGB_scheme

### cool_wind_AGB_scheme

This section replaces the old “`RGB_wind_scheme`

” and “`AGB_wind_scheme`

”
with temperature-dependent hot_wind and cool_wind. You can still
use the RGB and AGB wind scheme as before, the functionality remains.

Now you can also select a hot wind scheme that takes effect *above*
some temperature, set by `hot_wind_full_on_T`

.
Similarly, the cool wind scheme has temperature controls that
set the temperature *below* which they are relevant (`cool_wind_full_on_T`

).

As before, an empty string ‘’ means no wind.

The wind “eta” values, which are constant scaling factors, have all renamed *_wind_eta -> *_scaling_factor.

Here is an example of how to translate an existing inlist from the old style to the new:

Before

After

RGB_wind_scheme = ‘Reimers’ Reimers_wind_eta = 0.1 AGB_wind_scheme = ‘Blocker’ Blocker_wind_eta = 0.5 RGB_to_AGB_wind_switch = 1d-4

cool_wind_RGB_scheme = ‘Reimers’ Reimers_scaling_factor = 0.1 cool_wind_AGB_scheme = ‘Blocker’ Blocker_scaling_factor = 0.5 RGB_to_AGB_wind_switch = 1d-4

! only use the cool_wind_scheme cool_wind_full_on_T = 1d10 !K hot_wind_full_on_T = 1.1d10 !K hot_wind_scheme = ‘’

suggested hot and cool wind schemes follow but any valid wind option will work for either hot or cool.

Empty string means no wind

Suggested hot wind option:

‘Vink’

Suggested cool wind options:

‘Reimers’

‘Blöcker’

‘de Jager’

‘van Loon’

‘Nieuwenhuijzen’

For now the ‘Dutch’ scheme can be used in either capacity.

NOTE: for schemes that scale with metallicitity, we use Zbase rather than Z (as long as Zbase > 0). This is because wind mass loss rate is primarily determined by iron opacity, which is unlikely to change during the evolution.

```
hot_wind_scheme = ''
cool_wind_RGB_scheme = ''
cool_wind_AGB_scheme = ''
```

### cool_wind_full_on_T

### hot_wind_full_on_T

NOTE: hot_wind_full_on_T was previously called ‘cool_wind_full_off_T’

use only cool wind schemes for T_phot < `cool_wind_full_on_T`

use only hot wind schemes for T_phot > `hot_wind_full_on_T`

if `cool_wind_full_on_T`

/= `hot_wind_full_on_T`

then ramp between these limits
requires `hot_wind_full_on_T`

> `cool_wind_full_on_T`

```
cool_wind_full_on_T = 0.8d4
hot_wind_full_on_T = 1.2d4
```

### RGB_to_AGB_wind_switch

If center hydrogen abundance is < 0.01
and center helium abundance by mass is less than `RGB_to_AGB_wind_switch`

,
then system will use `AGB_wind_scheme`

rather than `RGB_wind_scheme`

.

```
RGB_to_AGB_wind_switch = 1d-4
```

The code will automatically choose between an RGB wind and an AGB wind. The following names for the different schemes are recognized:

‘Reimers’

‘Blocker’

‘de Jager’

‘van Loon’

‘Nieuwenhuijzen’

‘Vink’

‘Dutch’

‘other’ — for wind options implemented using other_wind hook

### Reimers_scaling_factor

Reimers mass loss for red giants.

D. Reimers “Problems in Stellar Atmospheres and Envelopes” Baschek, Kegel, Traving (eds), Springer, Berlin, 1975, p. 229.

Parameter for mass loss by Reimers wind prescription.
Reimers mdot is `eta*4d-13*L*R/M`

(Msun/year), with L, R, and M in solar units.
Typical value is 0.5.

```
Reimers_scaling_factor = 0
```

### Blocker_scaling_factor = 0

Blocker’s mass loss for AGB stars.

T. Blocker “Stellar evolution of low and intermediate-mass stars” A&A 297, 727-738 (1995).

Parameter for mass loss by Blocker’s wind prescription.
Blocker mdot is `eta*4.83d-9*M**-2.1*L**2.7*4d-13*L*R/M`

(Msun/year),
with L, R, and M in solar units.
Typical value is 0.1d0.

```
Blocker_scaling_factor = 0
```

### de_Jager_scaling_factor

de Jager mass loss for various applications. de Jager, C., Nieuwenhuijzen, H., & van der Hucht, K. A. 1988, A&AS, 72, 259. Parameter for mass loss by de Jager wind prescription.

```
de_Jager_scaling_factor = 0d0
```

### van_Loon_scaling_factor

see van Loon et al. 2005, A&A, 438, 273 “An empirical formula for the mass-loss rates of dust-enshrouded red supergiants and oxygen-rich Asymptotic Giant Branch stars”

```
van_Loon_scaling_factor = 0d0
```

### Nieuwenhuijzen_scaling_factor

See Nieuwenhuijzen, H.; de Jager, C. 1990, A&A, 231, 134.

```
Nieuwenhuijzen_scaling_factor = 0d0
```

### Vink_scaling_factor

Vink, J.S., de Koter, A., & Lamers, H.J.G.L.M., 2001, A&A, 369, 574. “Mass-loss predictions for O and B stars as a function of metallicity”

```
Vink_scaling_factor = 0d0
```

### Dutch_scaling_factor

The “Dutch” wind scheme for massive stars combines results from several papers, all with authors mostly from the Netherlands.

The particular combination we use is based on Glebbeek, E., et al, A&A 497, 255-264 (2009) [more Dutch authors!]

For Teff > 1e4 and surface H > 0.4 by mass, use Vink et al 2001 Vink, J.S., de Koter, A., & Lamers, H.J.G.L.M., 2001, A&A, 369, 574.

For Teff > 1e4 and surface H < 0.4 by mass, use Nugis & Lamers 2000 Nugis, T.,& Lamers, H.J.G.L.M., 2000, A&A, 360, 227 Some folks use 0.8 for non-rotating mdoels (Maeder & Meynet, 2001).

```
Dutch_scaling_factor = 0d0
```

### Dutch_wind_lowT_scheme

For Teff < 1e4

Use de Jager if `Dutch_wind_lowT_scheme = 'de Jager'`

de Jager, C., Nieuwenhuijzen, H., & van der Hucht, K. A. 1988, A&AS, 72, 259.

Use van Loon if `Dutch_wind_lowT_scheme = 'van Loon'`

van Loon et al. 2005, A&A, 438, 273.

Use Nieuwenhuijzen if `Dutch_wind_lowT_scheme = 'Nieuwenhuijzen'`

Nieuwenhuijzen, H.; de Jager, C. 1990, A&A, 231, 134

```
Dutch_wind_lowT_scheme = 'de Jager'
```

### Kudritzki_scaling_factor

Radiation driven winds of hot stars. See Kudritzki et al, Astron. Astrophys. 219, 205-218 (1989). this is now implemented using the other_wind hook. see other_physics_hooks test case.

### Grafener_scaling_factor

Grafener, G. & Hamann, W.-R. 2008, A&A 482, 945 contributed to mesa by Nilou Afsari this is now implemented using the other_wind hook. see other_physics_hooks test case.

### Stern51_scaling_factor

this is now implemented using the other_wind hook. see other_physics_hooks test case.

### use_accreted_material_j

Angular momentum of accreted material.

```
use_accreted_material_j = .false.
```

If false, then accreted material is given j so that it
is rotating at the same angular velocity as the surface.
If true, then accreted material is given j = `accreted_material_j`

.

```
accreted_material_j = 0
```

### no_wind_if_no_rotation

Use this to delay start of wind until after have started rotation.

```
no_wind_if_no_rotation = .false.
```

### min_wind

Min wind in Msun/year > 0; ignore this limit if it is <= 0. e.g., might have low level wind even when normal scheme doesn’t call for any.

```
min_wind = 0d0
```

### max_wind

Max wind in Msun/year > 0; ignore this limit if it is <= 0.

```
max_wind = 0d0
```

For critical rotation mass loss
Redo step as needed to find mdot that brings model to just below critical.
if `max_mdot_redo_cnt`

> 0, and `surf_omega_div_omega_crit`

> `surf_omega_div_omega_crit_limit`

,
then recompute the step while increasing mdot, until
`surf_omega_div_omega_crit`

< `surf_omega_div_omega_crit_limit`

. Once an upper limit for mdot is found,
the solution for mdot is further refined by bisection until it is computed to a tolerance of
`surf_omega_div_omega_crit_tol`

. During iterations, mdot is adjusted alternately by multiplication
by `mdot_revise_factor`

, and by adjusting it by `implicit_mdot_boost*mdot_initial`

, where
`mdot_initial`

is the value of mdot at the first iteration. This is done to deal with mass
accreting stars, where mdot might need to change sign for the star to remain below critical.
This is a direct replacement for `surf_w_div_w_crit_limit`

and `surf_w_div_w_crit_tol`

```
max_mdot_redo_cnt = 0
min_years_dt_for_redo_mdot = 0
surf_omega_div_omega_crit_limit = 0.99d0
surf_omega_div_omega_crit_tol = 0.05d0
mdot_revise_factor = 1.1d0
implicit_mdot_boost = 0.1d0
```

#### implicit wind computation.

### max_tries_for_implicit_wind

The implicit method will modify the mass transfer rate and redo the step until
it either finds a solution, or the number of tries hits `max_tries_for_implicit_wind`

.
If `max_tries_for_implicit_wind = 0`

, the wind computation is explicit,
meaning that the value of mdot is set using values at the start of the step.
This only applies when mdot < 0.

```
max_tries_for_implicit_wind = 0
```

### iwind_tolerance

Tolerance for which a solution is considered valid. A solution is valid if

```
abs(explicit_mdot - implicit_mdot) <
abs(implicit_mdot)*iwind_tolerance
```

where

```
explicit_mdot = mstar_dot at start of step
implicit_mdot = mstar_dot at end of step
```

```
iwind_tolerance = 1d-3
```

### iwind_lambda

If do not satisfy tolerance, redo with a different mdot as follows:

- mstar_dot = explicit_mdot + &
iwind_lambda*(implicit_mdot - explicit_mdot)

```
iwind_lambda = 1d0
```

### super_eddington_scaling_factor

For super eddington wind we use Ledd averaged by mass to optical depth tau = `surf_avg_tau`

.

```
super_eddington_scaling_factor = 0
```

### super_eddington_wind_Ledd_factor

Parameter for mass loss driven by super Eddington luminosity. Divide L by this factor when computing super Eddington wind, e.g., if this is 2, then only get wind when L/2 > Ledd.

```
super_eddington_wind_Ledd_factor = 1
```

### wind_boost_full_off_L_div_Ledd

Boost off for L/Ledd <= this (set large to disable this).
This alternative form is used when `super_eddington_scaling_factor`

== 0.

```
wind_boost_full_off_L_div_Ledd = 1.5d0
```

### wind_boost_full_on_L_div_Ledd

Do max boost for L/Ledd >= this.
This alternative form is used when `super_eddington_scaling_factor`

== 0.

```
wind_boost_full_on_L_div_Ledd = 5
```

### super_eddington_wind_max_boost

Multiply wind mdot by up to this amount.
This alternative form is used when `super_eddington_scaling_factor`

== 0.

```
super_eddington_wind_max_boost = 1
```

### trace_super_eddington_wind_boost

Send super eddington wind information to terminal.

```
trace_super_eddington_wind_boost = .false.
```

### mass_change_full_on_dt

### mass_change_full_off_dt

These params provide the option to turn off mass change when have very small timesteps.
Between `mass_change_full_on_dt`

and `mass_change_full_off_dt`

mass change is gradually reduced.
Units in seconds.

```
mass_change_full_on_dt = 1d-99
mass_change_full_off_dt = 1d-99
```

### trace_dt_control_mass_change

```
trace_dt_control_mass_change = .false.
```

### max_star_mass_for_gain

Automatic stops for mass loss/gain in Msun units (negative means ignore this parameter). Turn off mass gain when star mass reaches this limit.

```
max_star_mass_for_gain = -1
```

### min_star_mass_for_loss

Automatic stops for mass loss/gain in Msun units (negative means ignore this parameter). Turn off mass loss when star mass reaches this limit.

```
min_star_mass_for_loss = -1
```

### max_T_center_for_any_mass_loss

No mass loss for T center > this.

```
max_T_center_for_any_mass_loss = 2d9
```

### max_T_center_for_full_mass_loss

No reduction in mass loss for T center <= this.
This must be <= `max_T_center_for_full_mass_loss`

.
Reduce mass loss rate to 0 as T center climbs from `max_for_full`

to `max_for_any`

.
The idea behind this is that during final stages of burning, there is so little time
left in the life of the star, that any mass loss to winds will be negligible,
but the inclusion of that insignificant mass loss can actually make
convergence more difficult, so you are better off without it.

```
max_T_center_for_full_mass_loss = 1d9
```

### wind_H_envelope_limit

Winds automatically shut off when star_mass - he_core_mass mass is less than this limit.
The value of `he_core_boundary_h1_fraction`

defines he_core_mass.
Mass in Msun units. Previously called `wind_envelope_limit`

.

```
wind_H_envelope_limit = -1
```

### wind_H_He_envelope_limit

Winds automatically shut off when star_mass - co_core_mass is less than this limit.
The value of `co_core_boundary_he4_fraction`

defines co_core_mass.
Mass in Msun units.

```
wind_H_He_envelope_limit = -1
```

### wind_He_layer_limit

Winds automatically shut off when he_core_mass - co_core_mass is less than this limit. Mass in Msun units.

```
wind_He_layer_limit = -1
```

### rlo_scaling_factor

Amplitude of mass loss. “rlo” wind scheme provides a simple radius-determined-wind with exponential increase.

```
rlo_scaling_factor = 0
```

### rlo_wind_min_L

Only on when L > this limit. (Lsun)

```
rlo_wind_min_L = 1d-6
```

### rlo_wind_max_Teff

Only on when Teff < this limit.

```
rlo_wind_max_Teff = 1d99
```

### rlo_wind_roche_lobe_radius

Only on when R > this (Rsun).

```
rlo_wind_roche_lobe_radius = 0.40d0
```

### rlo_wind_base_mdot

Base rate of mass loss when R = roche lobe radius (Msun/year).

```
rlo_wind_base_mdot = 1d-3
```

### rlo_wind_scale_height

Determines exponential growth rate of mass loss (Rsun).

```
rlo_wind_scale_height = 1d-1
```

### roche_lobe_xfer_full_on

Full accretion when R/RL <= this.
Limit accretion when Roche lobe is nearing full (only with `rlo_scaling_factor`

> 0).

```
roche_lobe_xfer_full_on = 0.5d0
```

### roche_lobe_xfer_full_off

No accretion when R/RL >= this.

```
roche_lobe_xfer_full_off = 1.0d0
```

#### controls for adjust_mass

### max_logT_for_k_below_const_q

### max_q_for_k_below_const_q

### min_q_for_k_below_const_q

Move `k_below_const_q`

inward from surface until `q(k) <= max_q`

.
Then continue moving inward until reach `logT(k) >= max_logT`

or `q(k) <= min_q`

.

```
max_logT_for_k_below_const_q = 5
max_q_for_k_below_const_q = 1.0d0
min_q_for_k_below_const_q = 0.999d0
```

### max_logT_for_k_const_mass

### max_q_for_k_const_mass

### min_q_for_k_const_mass

Move `k_const_mass`

inward from `k_below_const_q+1`

until `q(k) <= max_q`

.
Then continue moving inward until reach `logT(k) >= max_logT`

or `q(k) <= min_q`

.

```
max_logT_for_k_const_mass = 6
max_q_for_k_const_mass = 1.0d0
min_q_for_k_const_mass = 0.995d0
```

## composition controls

### accrete_same_as_surface

If true, composition of accreted material is identical to the current surface composition.
If false, then the composition is determined by `accrete_given_mass_fractions`

.

The actual mass accretion rate can be set up using the `mass_change`

option.

```
accrete_same_as_surface = .true.
```

### accrete_given_mass_fractions

If true, use `accrete_given_mass_fractions`

, `num_accretion_species`

,
`accretion_species_id`

and `accretion_species_xa`

to determine composition
of accreted material – they must add to 1.0.

If false, then the composition is determined using `accretion_h1`

, `accretion_h2`

,
`accretion_he3`

, `accretion_he4`

and `accretion_zfracs`

.

The actual mass accretion rate can be set up using the `mass_change`

option.

Note that this control is ignored if `accrete_same_as_surface`

is true.

```
accrete_given_mass_fractions = .false.
```

### num_accretion_species

### accretion_species_id

### accretion_species_xa

If accrete_same_as_surface is false and accrete_given_mass_fractions is true,
then composition of accreted material is determined by these options.
The actual mass accretion rate can be set up using the `mass_change`

option.

`num_accretion_species`

can be up to `s% max_num_accretion_species`

, see
`star/public/star_def.inc`

for the value of this parameter.

For each of `num_accretion_species`

, the id for the isotope needs to be specified
by `accretion_species_id`

as defined in `chem/public/chem_def.f90`

.

Mass fractions for each isotope are defined by `accretion_species_xa`

```
num_accretion_species = 0
accretion_species_id(1) = ''
accretion_species_xa(1) = 0
```

### accretion_h1

### accretion_h2

### accretion_he3

### accretion_he4

If accrete_same_as_surface is false and accrete_given_mass_fractions is false,
then the mass fractions of h1, h2, he3 and h4 are determined by these options.
Mass fractions for metals are set with the `accretion_zfracs`

control.
The actual mass accretion rate can be set up using the `mass_change`

option.

If no h2 in current net, then it is automatically added to h1.

```
accretion_h1 = 0
accretion_h2 = 0
accretion_he3 = 0
accretion_he4 = 0
```

### accretion_zfracs =

One of the following identifiers for different Z fractions from `chem_def`

.

`AG89_zfracs = 1`

, Anders & Grevesse 1989`GN93_zfracs = 2`

, Grevesse & Noels 1993`GS98_zfracs = 3`

, Grevesse & Sauval 1998`L03_zfracs = 4`

, Lodders 2003`AGS05_zfracs = 5`

, Asplund, Grevesse & Sauval 2005

or set `accretion_zfracs = 0`

to use the following list of z fractions

```
accretion_zfracs = -1
```

### accretion_dump_missing_metals_into_heaviest

this controls the treatment metals that are not included in the current net. if this flag is true, then the mass fractions of missing metals are added to the mass fraction of the most massive metal included in the net. if this flag is false, then the mass fractions of the metals in the net are renormalized to make up for the total mass fraction of missing metals.

```
accretion_dump_missing_metals_into_heaviest = .true.
```

Special list of z fractions. If you use these, they must add to 1.0.

```
z_fraction_li = 0
z_fraction_be = 0
z_fraction_b = 0
z_fraction_c = 0
z_fraction_n = 0
z_fraction_o = 0
z_fraction_f = 0
z_fraction_ne = 0
z_fraction_na = 0
z_fraction_mg = 0
z_fraction_al = 0
z_fraction_si = 0
z_fraction_p = 0
z_fraction_s = 0
z_fraction_cl = 0
z_fraction_ar = 0
z_fraction_k = 0
z_fraction_ca = 0
z_fraction_sc = 0
z_fraction_ti = 0
z_fraction_v = 0
z_fraction_cr = 0
z_fraction_mn = 0
z_fraction_fe = 0
z_fraction_co = 0
z_fraction_ni = 0
z_fraction_cu = 0
z_fraction_zn = 0
```

### lgT_lo_for_set_new_abundances

### lgT_hi_for_set_new_abundances

Composition controls for `set_new_abundances`

.

```
lgT_lo_for_set_new_abundances = 5.2d0
lgT_hi_for_set_new_abundances = 5.5d0
```

## mesh adjustment

### max_allowed_nz

Maximum number of grid points allowed.

```
max_allowed_nz = 8000
```

### remesh_max_allowed_logT

Turn off remesh if any cell has logT > this.

```
remesh_max_allowed_logT = 1d99
```

### mesh_max_allowed_ratio

Must be >= 2.5. Max ratio for mass of adjacent cells. If have ratio exceeding this, split the larger cell.

```
mesh_max_allowed_ratio = 2.5d0
```

### max_delta_x_for_merge

Don’t merge neighboring cells if any abundance differs by more than this.

```
max_delta_x_for_merge = 0.1d0
```

### mesh_delta_coeff

A larger value increases the max allowed deltas and decreases the number of grid points. and a smaller does the opposite.

analogous to time_delta_coeff for better time resolution.

E.g., you’ll roughly double the number of grid points if you cut `mesh_delta_coeff`

in half.
Don’t expect it to exactly double the number however since other parameters in addition to
gradients also influence the details of the grid spacing.

this factor also applies to max_dq, max_center_cell_dq, and max_surface_cell_dq.

```
mesh_delta_coeff = 1.0d0
```

### mesh_Pgas_div_P_exponent

Multiply `mesh_delta_coeff`

by (Pgas/Ptotal) to this power.

```
mesh_Pgas_div_P_exponent = 0
```

### mesh_delta_coeff_for_highT

Use different `mesh_delta_coeff`

at higher temperatures.

```
mesh_delta_coeff_for_highT = 3.0d0
```

### logT_max_for_standard_mesh_delta_coeff

Use `mesh_delta_coeff`

for center logT <= this. This value
should be less than `logT_min_for_highT_mesh_delta_coeff`

.

```
logT_max_for_standard_mesh_delta_coeff = 9.0d0
```

### logT_min_for_highT_mesh_delta_coeff

Use `mesh_delta_coeff_for_highT`

for center logT >= this.
Linearly interpolate in logT for intermediate center temperatures.

```
logT_min_for_highT_mesh_delta_coeff = 9.5d0
```

### max_dq

Max size for cell as fraction of total mass.

```
max_dq = 1d-2
```

### min_dq

Min size for cell as fraction of total mass.

```
min_dq = 1d-14
```

Min size for cell to be split.

```
min_dq_for_split = 1d-14
```

### min_dq_for_xa

Min size for splitting because of composition gradient. only for non-convective regions if have set min_dq_for_xa_convective > 0.

```
min_dq_for_xa = 1d-14
```

### min_dq_for_xa_convective

Min size for splitting because of composition gradient in convective regions. if <= 0, then use min_dq_for_xa instead of this.

```
min_dq_for_xa_convective = 1d-6
```

Min size for cell to be split because of jump in logT.

```
min_dq_for_logT = 1d-14
```

### mesh_min_dlnR

Limit on difference in lnR across cell for mesh refinement. Do not make this smaller than about 1d-14 or will fail with numerical problems.

```
mesh_min_dlnR = 1d-9
```

### merge_if_dlnR_too_small

If true, mesh adjustment will force merge if difference in lnR across cell is too small.

```
merge_if_dlnR_too_small = .false.
```

### mesh_min_dr_div_dRstar

Limit on relative radial extent for mesh refinement. dRstar = s% r(1) - s% R_center Don’t split if dr/dRstar would drop below this limit.

```
mesh_min_dr_div_dRstar = -1
```

### merge_if_dr_div_dRstar_too_small

If true, mesh adjustment will force merge if `dr_div_dRstar`

too small.

```
merge_if_dr_div_dRstar_too_small = .true.
```

### mesh_min_dr_div_cs

Limit (in seconds) on sound crossing time for mesh refinement. Don’t split if sound crossing time would drop below this limit.

```
mesh_min_dr_div_cs = -1
```

### merge_if_dr_div_cs_too_small

If true, mesh adjustment will force merge if `dr_div_cs`

too small.

```
merge_if_dr_div_cs_too_small = .true.
```

### max_center_cell_dq

Largest allowed dq at center.

```
max_center_cell_dq = 1d-7
```

### max_surface_cell_dq

Largest allowed dq at surface.

```
max_surface_cell_dq = 1d-12
```

### max_num_subcells

Limits number of new cells from 1 old one.

```
max_num_subcells = 2
```

### max_num_merge_cells

Limits number of old cells to merge into 1 new one.

```
max_num_merge_cells = 2
```

### mesh_adjust_get_T_from_E

If true, then use internal energy conservation to set new temperature. If false, just use average temperature based on reconstruction polynomials.

```
mesh_adjust_get_T_from_E = .true.
```

### mesh_ok_to_merge

### mesh_max_k_old_for_split

### mesh_min_k_old_for_split

```
mesh_ok_to_merge = .true.
mesh_max_k_old_for_split = 999999999
mesh_min_k_old_for_split = 0
```

### E_function_weight

internal energy gradient, `E_function = E_function_weight*max(E_function_param,log10(energy))`

.

```
E_function_weight = 0
E_function_param = 16d0
```

### P_function_weight

Pressure gradient, `P_function = P_function_weight*log10(P)`

.

```
P_function_weight = 40
```

### T_function1_weight

Temperature gradient, `T_function1 = T_function1_weight*log10(T)`

.
NOTE: The T gradient mesh controls below seems to be necessary to allow burning that starts off center
to be able to reach the center. You can see this in the `pre_zahb`

`test_suite`

case if you
try running it without the T function. The center temperature will fail to rise.

```
T_function1_weight = 110
```

### T_function2_weight

### T_function2_param

```
T_function2 = T_function2_weight*log10(T / (T + T_function2_param))
```

Largest change in `T_function2`

happens around `T = T_function2_param`

.
Default value puts this in the envelope ionization region.

```
T_function2_weight = 0
T_function2_param = 2d4
```

### R_function_weight

### R_function_param

log radius gradient

```
R_function = R_function_weight*log10(1 + (r/Rsun)/R_function_param)
```

```
R_function_weight = 0
R_function_param = 1d-4
```

### R_function2_weight

### R_function2_param1

### R_function2_param2

```
R_function2 = R_function2_weight*min(R_function2_param1,max(R_function2_param2,r/Rstar))
```

where Rstar = radius of outer edge of model.

```
R_function2_weight = 0
R_function2_param1 = 0.4d0
R_function2_param2 = 0
```

### R_function3_weight

radius gradient

```
R_function3 = R_function3_weight*(r/Rstar)
```

```
R_function3_weight = 0
```

### M_function_weight

### M_function_param

log mass gradient

```
M_function = M_function_weight*log10(1 + (m/Msun)/M_function_param)
```

```
M_function_weight = 0
M_function_param = 1d-6
```

### gradT_function_weight

gradT gradient, `gradT_function = gradT_function_weight*gradT`

```
gradT_function_weight = 0
```

### log_tau_function_weight

log_tau gradient (optical depth)

```
log_tau_function = log_tau_function_weight*log10(tau)
```

```
log_tau_function_weight = 0
```

### log_kap_function_weight

log_kap gradient (optical depth)

```
log_kap_function = log_kap_function_weight*log10(kap)
```

```
log_kap_function_weight = 0
```

### omega_function_weight

omega gradient (rotation omega in rad/sec)

```
omega_function = omega_function_weight*log10(omega)
```

```
omega_function_weight = 0
```

### gam_function_weight

### gam_function_param1

### gam_function_param2

For extra resolution around liquid/solid transition.

```
gam = plasma interaction parameter
gam_function = gam_function_weight*tanh((gam - gam_function_param1)/gam_function_param2)
```

```
gam_function_weight = 0
gam_function_param1 = 170
gam_function_param2 = 20
```

### xa_function_species

### xa_function_weight

Mass fraction gradients.

```
xa_function = xa_function_weight*log10(xa + xa_function_param),
```

Up to `num_xa_function`

of these - see `star_def`

for value of `num_xa_function`

.
0 length string means skip, otherwise name of nuclide as defined in `chem_def`

.
weight <= 0 means skip.

```
xa_function_species(:) = ''
xa_function_weight(:) = 0
```

```
xa_function_species(1) = 'he4'
xa_function_weight(1) = 30
xa_function_param(1) = 1d-2
```

### xa_mesh_delta_coeff

Useful if you want to increase `mesh_delta_coeff`

during advanced burning.
If `xa_function_species(j)`

has the largest atomic number in current set of species,
then multiply `mesh_delta_coeff`

by `xa_mesh_delta_coeff(j)`

.

```
xa_mesh_delta_coeff(:) = 1
```

### mesh_delta_coeff_factor_smooth_iters

Some smoothing is useful when using local changes to mesh_delta_coeff.

```
mesh_delta_coeff_factor_smooth_iters = 3
```

“Indirect” mesh controls work by increasing sensitivity in selected regions.
They work in the same way as `mesh_delta_coeff`

– values less than 1.0 mean
smaller allowed jumps in mesh functions and hence smaller grid points and
higher resolution. But whereas `mesh_delta_coeff`

applies uniformly to all
cells, the “extra” coefficients can vary in value from one cell to the next.

Note that you can set your own local changes by means of the hook other_mesh_delta_coeff_factor.

### mesh_logX_species

### mesh_logX_min_for_extra

Increase resolution at points with large abs(dlogX/dlogP); logX = log10(X mass fraction).

```
mesh_logX_species(1) = ''
mesh_logX_min_for_extra(1) = -6
```

### mesh_dlogX_dlogP_extra(1)

### mesh_dlogX_dlogP_full_on(1)

### mesh_dlogX_dlogP_full_off(1)

Only increase resolution if `logX >= mesh_logX_min_for_extra`

.
Make `mesh_dlogX_dlogP_extra < 1`

for smaller allowed change in logP and hence higher resolution.
Full effect if `abs(dlogX/dlogP) >= mesh_dlogX_dlogP_full_on`

.
No effect if `abs(dlogX/dlogP)) <= mesh_dlogX_dlogP_full_off`

.
Up to `num_mesh_logX`

of these (see `star_def`

for value of `num_mesh_logX`

).

```
mesh_dlogX_dlogP_extra(1) = 1
mesh_dlogX_dlogP_full_on(1) = 2
mesh_dlogX_dlogP_full_off(1) = 1
```

Multiply `mesh_delta_coeff`

near convection zone boundary (czb) by the following factors.
Value < 1 gives increased resolution.

Increase resolution at points with large `abs(dlog_eps/dlogP)`

for nuclear power eps (ergs/g/sec).
At any particular location, only use eps nuc category with max local value
e.g., only use `mesh_dlog_pp_dlogP_extra`

at points where pp is the max burn source.

### mesh_dlog_eps_min_for_extra

Only increase resolution if `log_eps >= mesh_dlog_eps_min_for_extra`

.

```
mesh_dlog_eps_min_for_extra = -2
```

### mesh_dlog_eps_dlogP_full_on

Full effect if `abs(dlog_eps/dlogP) >= mesh_dlog_eps_dlogP_full_on`

.

```
mesh_dlog_eps_dlogP_full_on = 4
```

### mesh_dlog_eps_dlogP_full_off

No effect if `abs(dlog_eps/dlogP)) <= mesh_dlog_eps_dlogP_full_off`

.

```
mesh_dlog_eps_dlogP_full_off = 1
```

Multiply the allowed change between adjacent cells by the following factors; (small factor => smaller allowed change => more cells).

pp and cno burning

```
mesh_dlog_pp_dlogP_extra = 0.25d0
mesh_dlog_cno_dlogP_extra = 0.25d0
```

triple alpha, c, n, and o burning

```
mesh_dlog_3alf_dlogP_extra = 0.25d0
mesh_dlog_burn_c_dlogP_extra = 0.25d0
mesh_dlog_burn_n_dlogP_extra = 0.25d0
mesh_dlog_burn_o_dlogP_extra = 0.25d0
```

ne, na, and mg burning

```
mesh_dlog_burn_ne_dlogP_extra = 0.25d0
mesh_dlog_burn_na_dlogP_extra = 0.25d0
mesh_dlog_burn_mg_dlogP_extra = 0.25d0
```

c12+c12. c12+o16, and o16+o16 burning

```
mesh_dlog_cc_dlogP_extra = 0.25d0
mesh_dlog_co_dlogP_extra = 0.25d0
mesh_dlog_oo_dlogP_extra = 0.25d0
```

si to iron alog alpha chain burning

```
mesh_dlog_burn_si_dlogP_extra = 0.25d0
mesh_dlog_burn_s_dlogP_extra = 0.25d0
mesh_dlog_burn_ar_dlogP_extra = 0.25d0
mesh_dlog_burn_ca_dlogP_extra = 0.25d0
mesh_dlog_burn_ti_dlogP_extra = 0.25d0
mesh_dlog_burn_cr_dlogP_extra = 0.25d0
mesh_dlog_burn_fe_dlogP_extra = 0.25d0
```

photodisintegration burning

```
mesh_dlog_pnhe4_dlogP_extra = 0.25d0
mesh_dlog_other_dlogP_extra = 0.25d0
mesh_dlog_photo_dlogP_extra = 1
```

### convective_bdy_weight

### convective_bdy_dq_limit

### convective_bdy_min_dt_yrs

Mesh function to enhance resolution near convective boundaries

```
convective_bdy_weight = 0
convective_bdy_dq_limit = 3d-5
convective_bdy_min_dt_yrs = 1d-3
```

### max_rel_delta_IE_for_mesh_total_energy_balance

remeshing can adjust internal energy of cell by this fraction in order to maintain total internal + potential + kinetic energy.

```
max_rel_delta_IE_for_mesh_total_energy_balance = 0.05d0
```

### trace_mesh_adjust_error_in_conservation

If true, report relative errors for total PE, KE, and IE. (potential, kinetic, internal).

```
trace_mesh_adjust_error_in_conservation = .false.
```

### okay_to_remesh

If false, then no remeshing.

```
okay_to_remesh = .true.
```

### restore_mesh_on_retry

If true, then after a retry the remeshing is undone for the step, and the following try is performed with the same mesh used in the previous step. This can help with the retry by reducing the changes.

```
restore_mesh_on_retry = .false.
```

### num_steps_to_hold_mesh_after_retry

When restore_mesh_on_retry=true, then after a retry remeshing is not done for this number of steps.

```
num_steps_to_hold_mesh_after_retry = 0
```

### remesh_dt_limit

No remesh if `dt < remesh_dt_limit`

, in seconds.

```
remesh_dt_limit = -1
```

### use_split_merge_amr

```
use_split_merge_amr = .false.
```

### split_merge_amr_logtau_zoning

### split_merge_amr_log_zoning

### split_merge_amr_hybrid_zoning

### split_merge_amr_flipped_hybrid_zoning

if split_merge_amr_logtau_zoning, target is even grid spacing in logtau else if split_merge_amr_log_zoning, target is even grid spacing in logr else if split_merge_amr_hybrid_zoning, target is even r spacing for core, even logr outside else if split_merge_amr_flipped_hybrid_zoning, target is even logr spacing for core, even r outside else target is even grid spacing in r

```
split_merge_amr_logtau_zoning = .false.
split_merge_amr_log_zoning = .true.
split_merge_amr_hybrid_zoning = .false.
split_merge_amr_flipped_hybrid_zoning = .false.
```

### split_merge_amr_nz_baseline

### split_merge_amr_nz_r_core

### split_merge_amr_nz_r_core_fraction

### split_merge_amr_mesh_delta_coeff

```
split_merge_amr_nz_baseline = 1000
split_merge_amr_nz_r_core = 0d0 ! ignore if <= 0
split_merge_amr_nz_r_core_fraction = 0d0 ! ignore if <= 0; else r_core = r_center + fraction*(r(1) - r_center)
split_merge_amr_mesh_delta_coeff = 1d0 ! like mesh_delta_coeff, but for amr
```

### split_merge_amr_MaxLong

### split_merge_amr_MaxShort

split cell if ratio of actual/desired size is > split_merge_amr_MaxLong; ignore if <= 0 merge cell if ratio of desired/actual size is < split_merge_amr_MaxShort; ignore if <= 0 be careful to avoid inconsistent limits such as when a required split triggers a required merge. to be safe, make sure product of limits > 2.

```
split_merge_amr_MaxLong = 1.5d0
split_merge_amr_MaxShort = 1.5d0
```

### merge_amr_max_abs_du_div_cs

```
merge_amr_max_abs_du_div_cs = 0.1d0
```

### merge_amr_du_div_cs_limit_only_for_compression

If true, then merge_amr_max_abs_du_div_cs limit will only be considered for cells that would undergo compression

```
merge_amr_du_div_cs_limit_only_for_compression = .false.
```

### merge_amr_inhibit_at_jumps

```
merge_amr_inhibit_at_jumps = .false.
```

### merge_amr_ignore_surface_cells

### merge_amr_k_for_ignore_surface_cells

Merging surface cells can cause problems. If merge_amr_ignore_surface_cells is true, then the outermost merge_amr_k_for_ignore_surface_cells cells are ignored for merge.

```
merge_amr_ignore_surface_cells = .true.
merge_amr_k_for_ignore_surface_cells = 2
```

### split_merge_amr_avoid_repeated_remesh

If true, then after a cell has been merged or split, the resulting cell will not be considered in further remeshing for this step.

```
split_merge_amr_avoid_repeated_remesh = .false.
```

### split_merge_amr_dq_min

### split_merge_amr_dq_max

```
split_merge_amr_dq_min = 1d-14
split_merge_amr_dq_max = 1d0
```

### split_merge_amr_r_core_cm

```
split_merge_amr_r_core_cm = 1d8
```

### split_merge_amr_max_iters

```
split_merge_amr_max_iters = 100
```

### split_merge_amr_okay_to_split_1

### split_merge_amr_okay_to_split_nz

```
split_merge_amr_okay_to_split_1 = .true.
split_merge_amr_okay_to_split_nz = .true.
```

### equal_split_density_amr

```
equal_split_density_amr = .false.
```

### trace_split_merge_amr

```
trace_split_merge_amr = .false.
```

## nuclear reaction controls

### default_net_name

Name of base reaction network.
Each net corresponds to a file in `$MESA_DIR/data/net_data/nets`

.
Look in that directory to see your network options,
or learn how to create your own net.

```
default_net_name = 'basic.net'
```

### screening_mode

empty string means no screening

`' extended'`

: extends the Graboske (1973) method using results from Alastuey and Jancovici (1978), along with plasma parameters from Itoh et al (1979) for strong screening.`'salpeter'`

: weak screening only. following Salpeter (1954), with equations (4-215) and (4-221) of Clayton (1968).`'chugunov'`

: based on code from Sam Jones Implements screening from Chugunov et al (2007) for weak and strong screening MESA versions <=11435 used extended as the default value

```
screening_mode = 'chugunov'
```

### net_logTcut_lo

strong rates are zero `logT < logTcut_lo`

use default from net if this is <= 0

```
net_logTcut_lo = -1
```

### net_logTcut_lim

strong rates cutoff smoothly for `logT < logTcut_lim`

use default from net if this is <= 0

```
net_logTcut_lim = -1
```

### max_abar_for_burning

if abar > this, suppress all burning e.g., if want an “inert” core heavy elements, set this to 55 or, if want to turn off the net, set this to -1

```
max_abar_for_burning = 199
```

### dxdt_nuc_factor

Control for abundance changes by burning.
Changes `dxdt_nuc`

(rate of change of abundances)
without changing the rates or `eps_nuc`

(rate of energy generation).

```
dxdt_nuc_factor = 1
```

### weak_rate_factor

all weak rates are multiplied by this factor

```
weak_rate_factor = 1
```

### reaction_neuQs_factor

all neutrino Q factors are multiplied by this factor

```
reaction_neuQs_factor = 1
```

### nonlocal_NiCo_kap_gamma

```
nonlocal_NiCo_kap_gamma = 0
```

### nonlocal_NiCo_decay_heat

if true, do non-local deposition of gamma-ray energy from Ni56 and Co56 decays. only for approx nets including co56. intended for use with stripped envelope supernovae.

```
nonlocal_NiCo_decay_heat = .false.
```

### dtau_gamma_NiCo_decay_heat

```
dtau_gamma_NiCo_decay_heat = 1d0
```

### max_logT_for_net

```
max_logT_for_net = 10.2d0
```

## element diffusion

gravitational settling and chemical diffusion.

### show_diffusion_info

terminal output for diffusion

```
show_diffusion_info = .false.
```

### show_diffusion_substep_info

terminal output for diffusion

```
show_diffusion_substep_info = .false.
```

### show_diffusion_timing

show time for each call on diffusion

```
show_diffusion_timing = .false.
```

### do_element_diffusion

determines whether or not we do element diffusion

```
do_element_diffusion = .false.
```

### diffusion_dt_limit

no element diffusion if dt < this limit (in seconds)

```
diffusion_dt_limit = 3.15d7
```

### diffusion_use_paquette

if true, use atomic diffusion coefficients according to Paquette et al. (1986). if false, use Stanton & Murillo PhRvE, 93, 043203 (2016) for diffusion coefficients. (Paquette coefficients still used for electron-ion because Stanton & Murillo did not do calculations for attractive potentials.)

```
diffusion_use_paquette = .false.
```

### diffusion_use_caplan

if true, use atomic diffusion coefficients according to Caplan, Bauer, & Freeman MNRAS, 513, L52 (2022) at strong coupling (Gamma > 10), relevant for white dwarf interiors.

```
diffusion_use_caplan = .true.
```

### diffusion_use_iben_macdonald

if true, use diffusion coefficients similar to Iben & MacDonald (1985).
if false, use Stanton & Murillo (2016) for diffusion coefficients.
this was previously called `diffusion_use_pure_coulomb`

.

```
diffusion_use_iben_macdonald = .false.
```

### diffusion_use_cgs_solver

if false, solve the system of equations described by Thoul et al. (1994) if true, solve the unmodified Burgers equations in cgs units

```
diffusion_use_cgs_solver = .true.
```

### cgs_thermal_diffusion_eta_full_on

### cgs_thermal_diffusion_eta_full_off

When `diffusion_use_cgs_solver = .true.`

for `eta < cgs_thermal_diffusion_eta_full_on`

,
includes the heat flow vector terms in the Burgers equations.
Then smoothly turns off use of these terms so that they are not included
for `eta > cgs_thermal_diffusion_eta_full_off`

, since these terms are
problematic when distribution function become non-Maxwellian.

```
cgs_thermal_diffusion_eta_full_on = 0d0
cgs_thermal_diffusion_eta_full_off = 2d0
```

### do_WD_sedimentation_heating

### min_xa_for_WD_sedimentation_heating

if true, include heating associated with sedimentation when element diffusion is on.
Only elements with mass fraction > min_xa_for_WD_sedimentation_heating
will be included in this calculation.
For best results, set diffusion_use_full_net = .true.
This will affect white dwarf cooling times.
See also `eps_WD_sedimentation_factor`

```
do_WD_sedimentation_heating = .false.
min_xa_for_WD_sedimentation_heating = 1d-5
```

### do_diffusion_heating

if true, calculate heating term associated with changes in internal energy due to any abundance changes from element diffusion, and include this term in the energy equation. To avoid double-counting, this control can only be used if do_WD_sedimentation_heating = .false.

```
do_diffusion_heating = .true.
```

### diffusion_min_dq_at_surface

treat at least this much at surface as a single cell for purposes of diffusion

```
diffusion_min_dq_at_surface = 1d-9
```

### diffusion_min_T_at_surface

treat cells cells at surface with T < this as a single cell for purposes of diffusion default should be large enough to ensure hydrogen ionization

```
diffusion_min_T_at_surface = 1d4
```

### diffusion_min_dq_ratio_at_surface

combine cells at surface until have total mass >= this factor times the next cell below them this helps with surface boundary condition for diffusion by putting large cell at surface

```
diffusion_min_dq_ratio_at_surface = 10
```

### diffusion_dt_div_timescale

dt is at most this fraction of timescale.
Each stellar evolution step can be divided into many substeps for diffusion.
The substep timescale is set by rates of flow in and out for each species in each cell.
The substep size, dt, is initially set to `timescale*diffusion_dt_div_timescale`

.

```
diffusion_dt_div_timescale = 1
```

### diffusion_min_num_substeps

Max substep dt is total time divided by this.

```
diffusion_min_num_substeps = 1
```

### diffusion_max_iters_per_substep

If the substep requires too many iterations, the substep time is decreased for a retry.

```
diffusion_max_iters_per_substep = 10
```

### diffusion_max_retries_per_substep

If the substep requires too many retries, diffusion fails and forces a retry for the star.

```
diffusion_max_retries_per_substep = 10
```

### diffusion_tol_correction_max

### diffusion_tol_correction_norm

Tolerances for solver iterations. Corrections smaller will be treated as converged. Corrections larger will cause another solver iteration.

```
diffusion_tol_correction_max = 1d-1
diffusion_tol_correction_norm = 1d-3
```

### diffusion_min_X_hard_limit

tolerance for negative mass fraction errors errors larger will cause retry; errors smaller will be corrected. Tightening this control may help with “failed in fixup” errors when diffusion_use_isolve = .true.

```
diffusion_min_X_hard_limit = -1d-3
```

### diffusion_X_total_atol

### diffusion_X_total_rtol

tolerances for errors in total species conservation errors larger will cause retry; errors smaller will be corrected.

```
diffusion_X_total_atol = 1d-9
diffusion_X_total_rtol = 1d-6
```

### diffusion_upwind_abs_v_limit

switch to upwind for i at face k if abs(v(i,k)) > this limit mainly for use with radiative levitation where get very much higher velocities

```
diffusion_upwind_abs_v_limit = 1d99
```

### diffusion_v_max

Max velocity (cm/sec).
We can get extremely large velocities in the extreme outer envelope
that cause problems numerically without really effecting the results,
so we allow a max for the velocities that should help the numerics
without changing the results.
Note: change `diffusion_v_max`

to at least 1d-2 when using radiative levitation.

```
diffusion_v_max = 1d-3
```

### D_mix_ignore_diffusion

Diffusion is turned off in core and surface convection zones, since it is overwhelmed by other mixing there. D_mix_ignore_diffusion roughly defines the mixing coefficient below which diffusion is included again. The code finds the location where D_mix falls to this value, backs up some, and turns on diffusion from there onward.

```
D_mix_ignore_diffusion = 1d5
```

### diffusion_gamma_full_off

### diffusion_gamma_full_on

`gamma_full_on <= gamma_full_off`

Shut off diffusion for large gamma (i.e. for `gamma >= gamma_full_off`

).
Gradually decrease diffusion as gamma increases from `full_on`

to `full_off`

.
Allow normal diffusion for `gamma <= gamma_full_on`

.
Default is diffusion off when get well into liquid regime.

```
diffusion_gamma_full_off = 1d99
diffusion_gamma_full_on = 1d99
```

### diffusion_T_full_on

### diffusion_T_full_off

`T_full_on >= T_full_off`

Shut off diffusion for small T (i.e., for `T <= T_full_off`

)
Gradually decrease diffusion as T decreases from `T_full_on`

to `T_full_off`

.
Allow normal diffusion for `T >= T_full_on`

.

```
diffusion_T_full_on = 1d3
diffusion_T_full_off = 1d3
```

### diffusion_calculates_ionization

If `diffusion_calculates_ionization`

is false, MESA uses
typical charges for a set of representative species as
defined in `diffusion_class_typical_charge`

and
`diffusion_class_representative`

for all points rather than
calculating the ionization from the local conditions.

```
diffusion_calculates_ionization = .true.
```

### diffusion_nsmooth_typical_charge

smoothing over charge

```
diffusion_nsmooth_typical_charge = 10
```

### diffusion_SIG_factor

### diffusion_GT_factor

factors for playing with SIG and GT terms for concentration diffusion and advection

```
diffusion_SIG_factor = 1d0
diffusion_GT_factor = 1d0
```

### diffusion_AD_dm_full_on

### diffusion_AD_dm_full_off

### diffusion_AD_boost_factor

artificial concentration diffusion near surface (mainly for radiative levitation)
Msun units for `full_on`

and `full_off`

boost only used if > 0

```
diffusion_AD_dm_full_on = -1
diffusion_AD_dm_full_off = -1
diffusion_AD_boost_factor = 0
```

### diffusion_Vlimit_dm_full_on

### diffusion_Vlimit_dm_full_off

in Msun units artificial velocity limitation near surface (mainly for radiative levitation)

```
diffusion_Vlimit_dm_full_on = -1
diffusion_Vlimit_dm_full_off = -1
```

### diffusion_Vlimit

In units of local cell crossing velocity (only used if > 0).
When full on, limit `abs(v) <= Vlimit*dr/dt`

, cell size dr, substep time dt.

```
diffusion_Vlimit = 0
```

### D_mix_zero_region_bottom_q

### D_mix_zero_region_top_q

### dq_D_mix_zero_at_H_He_crossover

### dq_D_mix_zero_at_H_C_crossover

```
D_mix_zero_region_bottom_q = 1d99
D_mix_zero_region_top_q = -1d99
dq_D_mix_zero_at_H_He_crossover = -1d0
dq_D_mix_zero_at_H_C_crossover = -1d0
```

### diffusion_min_T_for_radaccel

### diffusion_max_T_for_radaccel

If T between these limits, then include radiative levitation at that location.
Calculation of radiative levitation is costly, so only use it where necessary.
Note: change `diffusion_v_max`

to at least 1d-2 when using radiative levitation.

Note that radiative levitation requires OP calculations of g_rad for each class, and only 17 elements are supported (H, He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Cr, Mn, Fe, Ni). If you want to include radiative levitation, your options are: + Define diffusion classes such that all class representatives are among the 17 elements listed above. + Use a net with only elements from the 17 above, and set diffusion_use_full_net = .true.

```
diffusion_min_T_for_radaccel = 0
diffusion_max_T_for_radaccel = 0
```

### diffusion_min_Z_for_radaccel

### diffusion_max_Z_for_radaccel

If Z between these limits, then include radiative levitation for that element.
Calculation of radiative levitation is costly, so only use it where necessary.
e.g., limit to Fe and Ni by `min_Z = 26`

and `max_Z = 28`

```
diffusion_min_Z_for_radaccel = 0
diffusion_max_Z_for_radaccel = 1000
```

### diffusion_screening_for_radaccel

Include screening for radiative levitation.

```
diffusion_screening_for_radaccel = .true.
```

### diffusion_use_full_net

If true, don’t lump elements into classes for diffusion. Instead, each isotope in the network is treated as its own separate class. This can cause significant slowdowns for large nets, so it is off by default. This works for nets with up to 100 isotopes; larger nets require lumping into classes.

```
diffusion_use_full_net = .false.
```

### diffusion_num_classes

Number of representative classes of species for diffusion calculations. (maximum of 100)

```
diffusion_num_classes = 5
```

### diffusion_class_representative(:)

isotope names for diffusion representatives

```
diffusion_class_representative(1) = 'h1'
diffusion_class_representative(2) = 'he3'
diffusion_class_representative(3) = 'he4'
diffusion_class_representative(4) = 'o16'
diffusion_class_representative(5) = 'fe56'
```

### diffusion_class_A_max(:)

atomic number A. in ascending order. species goes into 1st class with `A_max`

>= species A

```
diffusion_class_A_max(1) = 2
diffusion_class_A_max(2) = 3
diffusion_class_A_max(3) = 4
diffusion_class_A_max(4) = 16
diffusion_class_A_max(5) = 10000
```

### diffusion_class_typical_charge(:)

Typical charges for use if `diffusion_calculates_ionization`

is false
Use charge 21 for Fe in the sun, from
Thoul, Bahcall, and Loeb (1994), ApJ, 421, 828.

```
diffusion_class_typical_charge(1) = 1
diffusion_class_typical_charge(2) = 2
diffusion_class_typical_charge(3) = 2
diffusion_class_typical_charge(4) = 8
diffusion_class_typical_charge(5) = 21
```

### diffusion_class_factor(:)

Arbitrarily enhance or inhibit diffusion effects by class.

```
diffusion_class_factor(:) = 1d0
```

#### parameters for ionization solver

### diffusion_use_isolve

Activate iterative solver.

```
diffusion_use_isolve = .false.
```

### diffusion_rtol_for_isolve

### diffusion_atol_for_isolve

Relative and absolute error parameters for iterative solver.

```
diffusion_rtol_for_isolve = 1d-4
diffusion_atol_for_isolve = 1d-5
```

### diffusion_maxsteps_for_isolve

Maximum number of steps to take in iterative solver.

```
diffusion_maxsteps_for_isolve = 1000
```

### diffusion_isolve_solver

Which ode solver to use for iterative.

Options include:

`'ros2_solver'`

`'rose2_solver'`

`'ros3p_solver'`

`'ros3pl_solver'`

`'rodas3_solver'`

`'rodas4_solver'`

`'rodasp_solver'`

```
diffusion_isolve_solver = 'ros2_solver'
```

### diffusion_dump_call_number

debugging info of diffusion at call number

```
diffusion_dump_call_number = -1
```

## WD phase separation

### do_phase_separation

Phase separation upon crystallization in WD cores (currently only for C/O white dwarf cores) using the implementation of Bauer (2023) with the phase diagram of Blouin et al. (2021).

```
do_phase_separation = .false.
```

### do_phase_separation_heating

if true, calculate heating term associated with changes in internal energy due to any abundance changes from phase separation, and include this term in the energy equation.

```
do_phase_separation_heating = .true.
```

### phase_separation_mixing_use_brunt

if true, the phase separation mixing recalculates relevant EOS quantities and evaluates the Ledoux criterion, including the brunt B term that depends on the composition gradient. This can be somewhat expensive, so this option can be set to false to instead just mix outward until there is no more negative mu gradient. These will produce similar final chemical profiles, but setting this option to true is the only way to properly evaluate the physical criterion.

```
phase_separation_mixing_use_brunt = .true.
```

## eos controls

### fix_d_eos_dxa_partials

The star solver uses the partial derivatives of lnPgas and lnE with respect to composition. When the EOS fails to provide these, replace them with a finite-difference approximation.

```
fix_d_eos_dxa_partials = .true.
```

## opacity controls

more opacity controls can be found in `star_job.defaults`

### use_simple_es_for_kap

for experiments with simple electron scattering
if true, `opacity = 0.2*(1 + X)`

```
use_simple_es_for_kap = .false.
```

### use_starting_composition_for_kap

for experiments with partials of opacity with respect to composition if true, calls on kap during solver iterations use the starting composition

```
use_starting_composition_for_kap = .false.
```

### opacity_max

limit opacities to this value (ignore this is value is < 0)

```
opacity_max = -1
```

### opacity_factor

opacities are multiplied by this value

```
opacity_factor = 1
```

### min_logT_for_opacity_factor_off

### min_logT_for_opacity_factor_on and

### max_logT_for_opacity_factor_on

### max_logT_for_opacity_factor_off

temperature controls for where the `opacity_factor`

is applied
if, for example, you only want the opacity factor to apply in the iron bump region
you can give a logT range such as

```
min_logT_for_opacity_factor_off = 5.2
min_logT_for_opacity_factor_on = 5.3
max_logT_for_opacity_factor_on = 5.7
max_logT_for_opacity_factor_off = 5.8
```

ignore these if < 0.

```
min_logT_for_opacity_factor_off = -1
min_logT_for_opacity_factor_on = -1
max_logT_for_opacity_factor_on = -1
max_logT_for_opacity_factor_off = -1
```

if you need cell-by-cell control of opacity factor,
set the vector “`extra_opacity_factor`

” using the routine “`other_opacity_factor`

”

#### OP mono opacities

The `OP_mono`

opacities use data and code from the OP website
as modified by Haili Hu. Since the tar.gz file is large (656 MB),
it is not included in the standard mesa download.

You can get `OP4STARS_1.3.tar.xz`

from https://zenodo.org/records/4390522

Put it any place you want on your disk.

```
tar -xf OP4STARS_1.3.tar.xz
```

Set the inlist controls for the “mono” directory with the data files. For example, in my case it looks like the following, but you can put the directory anywhere you like – it doesn’t need to be in the mesa/data directory. And the cache file doesn’t need to be in the mono directory.

```
op_mono_data_path = '/Users/bpaxton/OP4STARS_1.3/mono'
op_mono_data_cache_filename = '/Users/bpaxton/OP4STARS_1.3/mono/op_mono_cache.bin'
```

If you use these opacities, you should cite Seaton (2005).

### op_mono_data_path

if this path is set to the empty string, ‘’, then it defaults to the
environment variable `$(MESA_OP_MONO_DATA_PATH)`

```
op_mono_data_path = '' ! '' defaults to $MESA_OP_MONO_DATA_PATH
```

### op_mono_data_cache_filename

if this is set to the empty string, ‘’, then it defaults to the
environment variable `$(MESA_OP_MONO_DATA_CACHE_FILENAME)`

```
op_mono_data_cache_filename = '' ! '' defaults to $MESA_OP_MONO_DATA_CACHE_FILENAME
```

### op_mono_method

Compute the Rosseland mean opacity and radiative accelerations from the OP mono data by brute force (`'hu'`

)
or use the faster method by allowing for a small tolerance on the mixture used for the computations of these variables (`'mombarg'`

).

```
op_mono_method = 'hu'
```

### emesh_data_for_op_mono_path

path to the OP_mono_master_grid_MESA_emesh.txt file containing the data need for when op_mono_method = `'mombarg'`

.
If this is set to the empty string, ‘’, then it defaults to the
environment variable `$(MESA_OP_MONO_MASTER_GRID)`

You can get OP_mono_master_grid_MESA_emesh.txt from https://doi.org/10.5281/zenodo.6850861

You can either download the uncompressed `.txt`

file, or download the compressed `.xz`

file
and then unpack it in place with `unxz -v OP_mono_master_grid_MESA_emesh.txt.xz`

```
emesh_data_for_op_mono_path = '' ! '' defaults to $MESA_OP_MONO_MASTER_GRID
```

### high_logT_op_mono_full_off

### high_logT_op_mono_full_on

### low_logT_op_mono_full_off

### low_logT_op_mono_full_on

you can select a range of log10T for using `op_mono`

opacities
outside that range, the code will use standard opacity tables.
for example, you might only use high T limits so that `op_mono`

is only used in the envelope, or you might set both low and
high T limits so that `op_mono`

is used around the Fe peak logT
but not for other locations in the star.

```
high_logT_op_mono_full_off >= high_logT_op_mono_full_on
high_logT_op_mono_full_on >= low_logT_op_mono_full_on
low_logT_op_mono_full_on >= low_logT_op_mono_full_off
```

```
op_mono opacities full on if
log10T <= high_logT_op_mono_full_on
and
log10T >= low_logT_op_mono_full_on
```

```
op_mono opacities full off if
log10T >= high_logT_op_mono_full_off
or
log10T <= low_logT_op_mono_full_off
```

partially on for other cases Note: OP mono ignored if either high_logT control < 0

```
high_logT_op_mono_full_off = -99
high_logT_op_mono_full_on = -99
```

```
low_logT_op_mono_full_off = -99
low_logT_op_mono_full_on = -99
```

### op_mono_min_X_to_include

skip iso if mass fraction < this

```
op_mono_min_X_to_include = 1d-20
```

### use_op_mono_alt_get_kap

if true, call the `op_mono_alt_get_kap`

routine instead of `op_mono_get_kap`

.
see `mesa/kap/public/kap_lib.f`

for details about these routines.

```
use_op_mono_alt_get_kap = .false.
```

### min_kap_for_dPrad_dm_eqn

```
min_kap_for_dPrad_dm_eqn = 1d-4
```

## asteroseismology controls

### get_delta_nu_from_scaled_solar

use scaled solar values

```
get_delta_nu_from_scaled_solar = .false.
```

### nu_max_sun

solar value of `nu_max`

```
nu_max_sun = 3100d0
```

### delta_nu_sun

solar value of `delta_nu`

```
delta_nu_sun = 135d0
```

### Teff_sun

solar value of Teff

```
Teff_sun = 5777d0
```

### delta_Pg_mode_freq

uHz. if <=0, use nu_max from scaled solar value

```
delta_Pg_mode_freq = 0d0
```

#### Brunt controls

### calculate_Brunt_B

### calculate_Brunt_N2

Only calculate if this is true.

```
calculate_Brunt_B = .true.
calculate_Brunt_N2 = .true.
```

### brunt_N2_coefficient

Standard N2 is multiplied by this value.

```
brunt_N2_coefficient = 1
```

### num_cells_for_smooth_brunt_B

Number of cells on either side to use in weighted smoothing of `brunt_B`

.

```
num_cells_for_smooth_brunt_B = 2
```

### threshold_for_smooth_brunt_B

Threshold for weighted smoothing of `brunt_B`

. Only apply smoothing (controlled
by `num_cells_for_smooth_brunt_B`

) for contiguous regions where \(|B|\) exceeds
this threshold. Might be useful for preventing narrow peaks from being excessively
broadened by smoothing

```
threshold_for_smooth_brunt_B = 0d0
```

### min_magnitude_brunt_B

If set `brunt_B`

to 0 if absolute value is < this.

```
min_magnitude_brunt_B = -1d99
```

## structure equations

### energy_eqn_option

Available options are `'dedt'`

or `'eps_grav'`

.
See below for descriptions of each form and form-specific options.

```
energy_eqn_option = 'dedt'
```

### dedt form

This form of the energy equation is used when `energy_eqn_option = 'dedt'`

.

It is a conservative equation for the local specific total energy introduced in MESA V, Section 3. See in particular Eq. (8) and surrounding discussion.

Because this equation is written in a conservative form, it should always do an
excellent job of numerical energy conservation. The error in numerical energy
conservation (quantified by `rel_E_err`

) reflects the energy equation
residuals (i.e., the extent to which the energy equation was not satisfied).
When using this form of the equation, models should generally have a small
(\(\lesssim 10^{-8}\)) value of `rel_E_err`

, roughly independent of space
and time resolution. A small value of `rel_E_err`

and its cumulative
counterpart `rel_run_E_err`

only demonstrates that the equation residuals are
small and is not evidence that a model is converged or reliable. Convergence
studies targeting the physical quantities of interest remain essential. A large
value of `rel_run_E_err`

(\(\gtrsim 10^{-2}\)) should be a cause for
concern and should be investigated further (see also
warn_when_large_rel_run_E_err and
max_abs_rel_run_E_err )

### no_dedt_form_during_relax

### dedt_eqn_r_scale

```
no_dedt_form_during_relax = .true.
dedt_eqn_r_scale = 1d8
```

### eps_grav form

This form of the energy equation is used when `energy_eqn_option = 'eps_grav'`

.

The quantity `eps_grav`

is defined as
\(\epsilon_{\rm grav} = -\frac{De}{Dt} - P \frac{DV_\rho}{Dt}\),
where \(e\) is the specific internal energy, \(P\) is the pressure,
\(V_\rho \equiv 1/\rho\) is the specific volume, and \(D/Dt\) is the
Lagrangian time derivative. See MESA IV, Section 8 for more discussion.

This quantity is then re-written into the following convenient-to-evaluate form (see MESA IV, eq. 63):

\(\epsilon_{\rm grav} = -T c_P \left[(1 - \nabla_{\rm ad} \chi_T)\frac{D\ln T}{Dt} - \nabla_{\rm ad} \chi_\rho \frac{D\ln \rho}{Dt}\right] + \epsilon_{\rm grav, X}\).

The final term reflects the change in internal energy due to changes in
composition (at fixed density and temperature) and is referred to in MESA as
`eps_grav_composition_term`

. It is defined as

\(\epsilon_{\rm grav, X} \equiv -\sum_i \left(\frac{\partial e}{\partial X_i}\right)_{\rho,T, \{X\ne X_i\}} \frac{DX_i}{Dt}\),

and MESA evaluates this term using the finite difference

\(\epsilon_{\rm grav, X} = -\frac{1}{\delta t}\left[e(\rho, T, X) - e(\rho, T, X_{\rm start})\right]\),

where \(\delta t\) is the timestep and \(X_{\rm start}\) is the start-of-step mass fractions. (Other quantities take their end-of-step values.)

Note: In a phase transition, `eps_grav`

includes the latent heat.

As with the `dedt`

form, the error in numerical energy conservation
(quantified by `rel_E_err`

) reflects the energy equation residuals (i.e., the
extent to which the energy equation was not satisfied). However, because this
version of the energy equation is not written in a conservative form, it also
includes error associated with the time discretization. An additional source of
error enters because the equation of state provided by the `eos`

module does
not precisely satisfy the mathematical and thermodynamic identities that are
used in rewriting the total and partial derivatives present in the equation.
This inconsistency is usually worst at the conditions where MESA blends
different component EOSes. It is important to understand that time
discretization error and eos inconsistencies also affect models using the
`dedt`

form of the energy equation but manifest in different ways (e.g., as
entropy generation). Under degenerate conditions, it is often preferable to
incur energy errors rather than entropy errors, and the `eps_grav`

form should
generally be preferred in such circumstances.

In practice, the error sources usually exhibit the ordering
(time discretization) > (eos inconsistency) >> (equation residuals).
With increasing time resolution, the time discretization error can be driven
down to the floor imposed by the eos inconsistency error. The value of this
floor depends on the physical conditions, but may be \(\sim 10^{-4}\), well
above the level of the residuals (\(\lesssim 10^{-8}\)). The control
use_time_centered_eps_grav provides a time-centered
implementation of `eps_grav`

that can often reach this floor at larger
timesteps. Convergence studies targeting the physical quantities of interest
remain essential.

### include_composition_in_eps_grav

If true, evaluate `eps_grav_composition_term`

and include this quantity in `eps_grav`

.

When this flag is true, the composition derivatives of `eps_grav`

are also
included in the Jacobian.

If this flag is set to false, the `eps_grav`

form will not conserve energy in
situations with changing composition.

```
include_composition_in_eps_grav = .true.
```

### use_time_centered_eps_grav

If true, use a time-centered version of `eps_grav`

and `eps_grav_composition_term`

.
(Disabled during relax.)

```
use_time_centered_eps_grav = .true.
```

### Gamma_lnS_eps_grav_full_off

### Gamma_lnS_eps_grav_full_on

Automatic switch to lnS form for eps_grav (\(\epsilon_{\rm grav} = -T\frac{Ds}{Dt}\)) in regions with high Gamma (plasma interaction parameter).
These controls only apply when using the PC EOS. This is necessary to get the
latent heat associated with the crystallization phase transition. The
composition term \(-\sum_i (\partial e/\partial Y_i)_{s,\rho} dY_i\) is
never included when the lnS form is used, independent of the setting of the
control `include_composition_in_eps_grav`

.

```
Gamma_lnS_eps_grav_full_on = 150d0
Gamma_lnS_eps_grav_full_off = 120d0
```

### eps_grav_factor

multiply eps_grav by this factor

```
eps_grav_factor = 1d0
```

### fix_eps_grav_transition_to_grid

fix_eps_grav_transition_to_grid = .false.

### velocity_q_upper_bound

Local override for global `v_flag`

.
If local q > this bound, local `v_flag`

is set false,
else local `v_flag`

is set to global `v_flag`

.
this lets you force v = 0 in outer envelope.

```
velocity_q_upper_bound = 1d99
```

### velocity_logT_lower_bound

Local override for global `v_flag`

.
If local logT < this bound, local `v_flag`

is set false,
else local `v_flag`

is set to global `v_flag`

.
this lets you force v = 0 in outer envelope.

```
velocity_logT_lower_bound = -1d99
```

### max_dt_yrs_for_velocity_logT_lower_bound

Only apply `velocity_logT_lower_bound`

when timestep < this limit.

```
max_dt_yrs_for_velocity_logT_lower_bound = 1d99
```

### use_gravity_rotation_correction

With rotation, multiply gravity by `fp_rot`

if this flag is true.
See the 2nd MESA paper (2013), equation 22.
previously called “use_dP_dm_rotation_correction”.

```
use_gravity_rotation_correction = .true.
```

### non_nuc_neu_factor

Multiplies power from non-nuclear reaction neutrinos. i.e., thermal neutrinos such as computed by mesa/neu.

```
non_nuc_neu_factor = 1
```

### eps_nuc_factor

Multiplies `eps_nuc`

without changing rates or `dxdt_nuc`

.
Thus controls energy production without modifying the amount of change in abundances.

```
eps_nuc_factor = 1
```

### eps_WD_sedimentation_factor

This controls energy production from sedimentation of Ne22 (and possibly other neutron-rich elements in WD interiors).

```
eps_WD_sedimentation_factor = 1
```

### max_abs_eps_nuc

Limit magnitude of eps_nuc to this.

```
max_abs_eps_nuc = 1d99
```

### fe56ec_fake_factor

### min_T_for_fe56ec_fake_factor

Multiplier on ni56 electron capture rate to take isotopes in hardwired networks to more neutron rich isotopes.

```
fe56ec_fake_factor = 1d-7
min_T_for_fe56ec_fake_factor = 3d9
```

### eps_mdot_factor

multiply eps_mdot by this factor

```
eps_mdot_factor = 1d0
```

### max_num_surf_revisions

Max number of forced reconverges for changes in `surf_lnS`

.

```
max_num_surf_revisions = 1
```

### max_abs_rel_change_surf_lnS

Force solver reconverge if surf_lnS changed more than this.

```
max_abs_rel_change_surf_lnS = 5d-4
```

### extra_power_source

erg/g/sec applied uniformly throughout the model
This can be used to push a pre-ms model up the track to lower center temperatures.
Can be used simultaneously with `inject_extra_ergs_sec`

and `inject_uniform_extra_heat`

```
extra_power_source = 0
```

### inject_uniform_extra_heat

extra heat in erg g^-1 s^-1
Added to cells in range `min_q_for_uniform_extra_heat`

to max.
Can be used simultaneously with `inject_extra_ergs_sec`

and `extra_power_source`

.

```
inject_uniform_extra_heat = 0
```

### min_q_for_uniform_extra_heat

sets bottom of region for `inject_uniform_extra_heat`

```
min_q_for_uniform_extra_heat = 0
```

### max_q_for_uniform_extra_heat

sets top of region for `inject_uniform_extra_heat`

```
max_q_for_uniform_extra_heat = 1
```

### inject_extra_ergs_sec

added to mass equal to `grams_for_inject_extra_core_ergs_sec`

can be used simultaneously with `extra_power_source`

and `inject_uniform_extra_heat`

```
inject_extra_ergs_sec = 0
```

### base_of_inject_extra_ergs_sec

(units: Msun) sets bottom of region for `inject_extra_ergs_sec`

note: actual base is at max of this and the center of the model

```
base_of_inject_extra_ergs_sec = 0
```

### total_mass_for_inject_extra_ergs_sec

(units: Msun) sets size of region for `inject_extra_ergs_sec`

```
total_mass_for_inject_extra_ergs_sec = 0
```

### start_time_for_inject_extra_ergs_sec

(units: sec) start time for injecting extra ergs/s

```
start_time_for_inject_extra_ergs_sec = -1d99
```

### duration_for_inject_extra_ergs_sec

(units: sec) length of time for injecting extra ergs/s set to negative value to keep injecting indefinitely or until reach target

```
duration_for_inject_extra_ergs_sec = -1
```

### inject_until_reach_model_with_total_energy

(units: ergs) target for model total energy
usually want to set `duration_for_inject_extra_ergs_sec = -1`

for this option.
continue injecting until total energy of model reaches min of
`inject_until_reach_model_with_total_energy`

, and
`initial total energy`

```
inject_until_reach_model_with_total_energy = 1d99
```

### steps_before_use_velocity_time_centering

### include_P_in_velocity_time_centering

### include_L_in_velocity_time_centering

### use_P_d_1_div_rho_form_of_work_when_time_centering_velocity

### P_theta_for_velocity_time_centering

### L_theta_for_velocity_time_centering

for time weighting in energy and momentum equations to give intrinsic conservation of total energy (conservation -> perfect as residuals -> 0), and to minimize numerical damping. as discussed in the 3rd mesa instrument paper (2015). time centering applies to velocities, pressures, and luminosities. not for u_flag. steps_before_use_velocity_time_centering < 0 means no time centering. P_theta and L_theta = 0.5 for time centered, = 1.0 for fully implicit.

```
steps_before_use_velocity_time_centering = -1
include_P_in_velocity_time_centering = .false.
P_theta_for_velocity_time_centering = 0.5d0
include_L_in_velocity_time_centering = .false.
L_theta_for_velocity_time_centering = 0.5d0
use_P_d_1_div_rho_form_of_work_when_time_centering_velocity = .false.
```

### use_dPrad_dm_form_of_T_gradient_eqn

### use_gradT_actual_vs_gradT_MLT_for_T_gradient_eqn

These are for alternatives ways to determine the T gradient. The standard form of the equation is

dT/dm = dP/dm * T/P * grad_T, grad_T = dlnT/dlnP from MLT.

use hydrostatic value for dP/dm in this. this is because of limitations of MLT for calculating grad_T. (MLT assumes hydrostatic equilibrium) see comment in K&W chpt 9.1.

The alternatives forms are for dynamic situations where the use of hydrostatic dP/dm is inappropriate. In order of priority,

With the resulting `L_rad`

, determine the expected dT/dm by

d_Prad/dm = -kap*L_rad/(clight*area^2) – see, e.g., K&W (5.12)

```
use_dPrad_dm_form_of_T_gradient_eqn = .false.
use_gradT_actual_vs_gradT_MLT_for_T_gradient_eqn = .false.
```

for hydro comparison tests (e.g., Sedov)

### Rayleigh-Taylor Instability

### RTI_A

### RTI_B

### RTI_C

### RTI_D

### RTI_C_X_factor

### RTI_C_X0

### RTI_max_alpha

### RTI_min_dm_behind_shock_for_full_on

### RTI_dm_for_center_alpha_nondecreasing

### RTI_energy_floor

### RTI_D_mix_floor

### RTI_min_m_for_D_mix_floor

### RTI_log_max_boost

### RTI_m_full_boost

### RTI_m_no_boost

Note that these parameters are not exactly the same as used by Paul Duffell. His calibrated D is 2, where mesa has default D = 3 (see mesaIV paper). Users should try various values since the choice is not clear cut.

```
RTI_A = 1d-3
RTI_B = 2.5d0
RTI_C = 0.2d0
RTI_D = 3d0
```

```
RTI_C_X0_frac = 0.9d0
RTI_C_X_factor = 0d0
```

```
RTI_max_alpha = 0.5d0
RTI_min_dm_behind_shock_for_full_on = 0d0
RTI_dm_for_center_eta_nondecreasing = 0.02d0
RTI_energy_floor = 0d0
RTI_D_mix_floor = 0d0
RTI_min_m_for_D_mix_floor = 0d0
```

```
RTI_log_max_boost = 3d0
RTI_m_full_boost = 4d0
RTI_m_no_boost = 5d0
```

### retry_for_v_above_clight

If .true., a retry will be triggered at the end of a step if the maximum velocity exceeds the speed of light. If .false., only a warning is printed.

```
retry_for_v_above_clight = .true.
```

## solver controls

the following is from a response on mesa-users to a question about controls for solver tolerances:

The “residual” is the left over difference between the left and right hand sides of the equation we are trying to solve. We do iterations to reduce that, but we are limited by the non-linearity of the problem and the quality of the estimates for the derivatives.

The “correction” is the change in the primary variable that is calculated using good-old Newton’s rule in multiple dimensions — so Jacobian and residuals give a correction that would make the next residual vanish if the problem were linear and the Jacobian was exact, neither of which are true. So the best we can hope for is that the corrections will get smaller next time.

The “norm” is the average; the “max” is the max. Sometimes you mainly care about the norm and will accept a few outliers. But sometimes you don’t want any really bad outliers, so you want to set a low limit for the max residual or correction as well as the norm.

You might want to try for several iterations with strict tolerances, and then relax them if things are still not converged. For example, you might be willing to live with the larger tolerances, but you’d like to give it a good try at the smaller ones before switching. Also, you might be willing to settle for any-old residual if the corrections have become small enough. You can do that too by relaxing the residual tolerances after a few iterations.

Hope that at least helps with the nomenclature.

I agree with Frank that you should consider the effects of smaller timesteps and more grid points as your main technique — tightening up the tolerances for the solver won’t help if you are taking timesteps that are too large or if you have inadequate grid resolution.

### tol_correction_norm

### tol_max_correction

“Correction” for variable x(i,k) is scaled change, dx(i,k)/xscale(i,k). these tolerances are for the magnitude of the scaled corrections.

```
tol_correction_norm = 3d-5
tol_max_correction = 3d-3
```

### tol_correction_high_T_limit

For very late stages of massive star evolution, need to relax tolerances. If max T >= this limit, switch scaling factors.

```
tol_correction_high_T_limit = 1d9
```

### tol_correction_norm_high_T

### tol_max_correction_high_T

Above `tol_correction_high_T_limit`

use these scaling factors.

```
tol_correction_norm_high_T = 3d-3
tol_max_correction_high_T = 3d-1
```

### tol_correction_extreme_T_limit

For very late stages of massive star evolution, need to relax tolerances. If center T >= this limit, switch scaling factors.

```
tol_correction_extreme_T_limit = 6d9
```

### tol_correction_norm_extreme_T

### tol_max_correction_extreme_T

For very late stages of massive star evolution, need to relax tolerances. If center T >= this limit, switch scaling factors.

```
tol_correction_norm_extreme_T = 8d-3
tol_max_correction_extreme_T = 8d-1
```

### tol_bad_max_correction

if `max_correction > tol_max_correction`

and no more iterations allowed,
then still accept the solution if `max_correction <= tol_bad_max_correction`

.
but if `max_correction > tol_bad_max_correction`

, then reject the solution.

```
tol_bad_max_correction = 0d0
```

### bad_max_correction_series_limit

If have this many steps in a row with `max_correction > tol_max_correction`

,
then do a retry with a smaller timestep.

```
bad_max_correction_series_limit = 2
```

### relax_use_gold_tolerances

```
relax_use_gold_tolerances = .false.
```

### relax_solver_iters_timestep_limit

### relax_tol_correction_norm

### relax_tol_max_correction

### relax_tol_residual_norm1

### relax_tol_max_residual1

### relax_iter_for_resid_tol2

### relax_tol_residual_norm2

### relax_tol_max_residual2

### relax_iter_for_resid_tol3

### relax_tol_residual_norm3

### relax_tol_max_residual3

### relax_maxT_for_gold_tolerances

For use during relax operations. Only used if /= 0.

```
relax_solver_iters_timestep_limit = 0
```

```
relax_tol_correction_norm = 0d0
relax_tol_max_correction = 0d0
```

```
relax_tol_residual_norm1 = 0d0
relax_tol_max_residual1 = 0d0
relax_iter_for_resid_tol2 = 3
```

```
relax_tol_residual_norm2 = 0d0
relax_tol_max_residual2 = 0d0
relax_iter_for_resid_tol3 = 0
```

```
relax_tol_residual_norm3 = 0d0
relax_tol_max_residual3 = 0d0
relax_maxT_for_gold_tolerances = -1d0
```

### include_L_in_correction_limits

### include_v_in_correction_limits

### include_u_in_correction_limits

### include_w_in_correction_limits

These variables can be excluded from calculation of correction norm and max.

```
include_L_in_correction_limits = .true.
include_v_in_correction_limits = .true.
include_u_in_correction_limits = .true.
include_w_in_correction_limits = .true.
```

### max_X_for_conv_timescale

### min_X_for_conv_timescale

### max_q_for_conv_timescale

### min_q_for_conv_timescale

### max_q_for_QHSE_timescale

### min_q_for_QHSE_timescale

```
max_X_for_conv_timescale = 1d0
min_X_for_conv_timescale = 0d0
max_q_for_conv_timescale = 1d0
min_q_for_conv_timescale = 0d0
max_q_for_QHSE_timescale = 1d0
min_q_for_QHSE_timescale = 0d0
```

### correction_xa_limit

Ignore correction to abundance when calculating correction norm and max if current mass fraction is less than this limit.

```
correction_xa_limit = 5d-3
```

### xa_scale

Scaling for abundance variables is `max(xa_scale, current mass fraction)`

.

```
xa_scale = 1d-5
```

### tol_residual_norm1

### tol_max_residual1

### iter_for_resid_tol2

“residual” for equation is the difference between left and right sides
use `tol_residual_norm1`

& `tol_max_residual1`

at iteration number `iter_for_resid_tol2`

, switch to next tolerances.

```
tol_residual_norm1 = 1d-10
tol_max_residual1 = 1d-9
iter_for_resid_tol2 = 6
```

### tol_residual_norm2

### tol_max_residual2

### iter_for_resid_tol3

Use `tol_residual_norm2`

& `tol_max_residual2`

these apply starting at iteration number `iter_for_resid_tol2`

.
at iteration number `iter_for_resid_tol3`

, switch to next tolerances.

```
tol_residual_norm2 = 1d90
tol_max_residual2 = 1d90
iter_for_resid_tol3 = 15
```

### tol_residual_norm3

### tol_max_residual3

Use `tol_residual_norm3`

& `tol_max_residual3`

these apply starting at iteration number `iter_for_resid_tol3`

.

```
tol_residual_norm3 = 1d90
tol_max_residual3 = 1d90
```

If things get worse from one iteration to next, give up. The following are the limits that define “getting worse enough to stop”.

### corr_norm_jump_limit

If correction norm increases by this factor or more, quit.

```
corr_norm_jump_limit = 1d99
```

### max_corr_jump_limit

If correction max increases by this factor or more, quit.

```
max_corr_jump_limit = 1d6
```

### resid_norm_jump_limit

If residual norm increases by this factor or more, quit.

```
resid_norm_jump_limit = 1d99
```

### max_resid_jump_limit

If residual max increases by this factor or more, quit.

```
max_resid_jump_limit = 1d6
```

### convergence_ignore_equL_residuals

```
convergence_ignore_equL_residuals = .false.
```

### convergence_ignore_alpha_RTI_residuals

```
convergence_ignore_alpha_RTI_residuals = .false.
```

### trace_solver_damping

Send solver damping data to screen.

```
trace_solver_damping = .false.
```

### do_normalize_dqs_as_part_of_set_qs

normalize_dqs destroys bit-for-bit read as inverse of write for models. ok for create pre ms etc., but not for read model create_pre_ms calls normalize_dqs even if this flag is false.

```
do_normalize_dqs_as_part_of_set_qs = .false.
```

use_DGESVX_in_bcyclic use_equilibration_in_DGESVX report_min_rcond_from_DGESXV

FOR DEBUGGING ONLY. NOT FOR GENERAL USE.

```
use_DGESVX_in_bcyclic = .false.
use_equilibration_in_DGESVX = .false.
report_min_rcond_from_DGESXV = .false.
```

### solver_max_tries_before_reject

Max number solver iterations before give up.

```
solver_max_tries_before_reject = 25
```

### max_tries1

Max tries on 1st model.

```
max_tries1 = 250
```

### max_tries_for_retry

Normal number of retries.

```
max_tries_for_retry = 25
```

### max_tries_after_5_retries

Increase number of tries after 5 failed ones.

```
max_tries_after_5_retries = 35
```

### max_tries_after_10_retries

Increase number of tries after 10 failed ones.

```
max_tries_after_10_retries = 50
```

### max_tries_after_20_retries

Increase number of tries after 20 failed ones.

```
max_tries_after_20_retries = 75
```

### retry_limit

Only use if > 0. In case the solver fails for some reason, it will retry with a smaller timestep. It does up to this many retries for the current step before terminating.

```
retry_limit = 100
```

### redo_limit

Only use if > 0. Do up to this many redo’s for the current step before terminating.

```
redo_limit = 100
```

### solver_itermin

Use at least this many iterations in solver for hydro solve.

```
solver_itermin = 2
```

### solver_itermin_until_reduce_min_corr_coeff

Use at least this many iterations in solver
before try using small `min_corr_coeff`

```
solver_itermin_until_reduce_min_corr_coeff = 8
```

### solver_reduced_min_corr_coeff

For use with `solver_itermin_for_reduce_min_corr_coeff`

.

```
solver_reduced_min_corr_coeff = 0.1d0
```

### tiny_corr_coeff_limit

### scale_correction_norm

### corr_param_factor

### scale_max_correction

### ignore_too_large_correction

### corr_coeff_limit

### tiny_corr_factor

### ignore_min_corr_coeff_for_scale_max_correction

### ignore_species_in_max_correction

### num_times_solver_reuse_mtx

see star/private/star_solver for info about these

```
tiny_corr_coeff_limit = 100
scale_correction_norm = 0.1d0
corr_param_factor = 10
scale_max_correction = 1d99
ignore_too_large_correction = .false.
corr_coeff_limit = 1d-2
tiny_corr_factor = 2
ignore_min_corr_coeff_for_scale_max_correction = .false.
ignore_species_in_max_correction = .false.
num_times_solver_reuse_mtx = 0
```

### min_xa_hard_limit

### min_xa_hard_limit_for_highT

If solver produces mass fraction < this limit, then reject the trial solution. Can optionally relax this limit at high T.

```
min_xa_hard_limit = -1d-5
min_xa_hard_limit_for_highT = -3d-5
```

### logT_max_for_xa_hard_limit

Use `min_xa_hard_limit`

for center logT <= this.

```
logT_max_for_min_xa_hard_limit = 9.49d0
```

### logT_min_for_xa_hard_limit_for_highT

Use `min_xa_hard_limit_for_highT`

for center logT >= this.
Linear interpolate in logT for intermediate center temperatures.

```
logT_min_for_min_xa_hard_limit_for_highT = 9.51d0
```

### sum_xa_hard_limit

### sum_xa_hard_limit_for_highT

If solver produces any cell with abs(sum(xa)-1) > this limit, then reject the trial solution. Can optionally relax this limit at high T.

```
sum_xa_hard_limit = 5d-4
sum_xa_hard_limit_for_highT = 1d-3
```

### logT_max_for_sum_xa_hard_limit

Use `sum_xa_hard_limit`

for center logT <= this.

```
logT_max_for_sum_xa_hard_limit = 9.40d0
```

### logT_min_for_sum_xa_hard_limit_for_highT

Use `sum_xa_hard_limit_for_highT`

for center logT >= this.
Linear interpolate in logT for intermediate center temperatures.

```
logT_min_for_sum_xa_hard_limit_for_highT = 9.44d0
```

### do_solver_damping_for_neg_xa

If true, uniformly reduce solver corrections if necessary to avoid neg abundances.

```
do_solver_damping_for_neg_xa = .true.
```

### scale_max_correction_for_negative_surf_lum

### max_frac_for_negative_surf_lum

If true, then scales the correction factor in a Newton iteration to prevent the surface from reaching a negative luminosity. If an iteration would require s% L(1) to become negative, then the correction is scaled such that the change in surface luminosity is -max_frac_for_negative_surf_lum*s% L(1)

```
scale_max_correction_for_negative_surf_lum = .false.
max_frac_for_negative_surf_lum = 0.8
```

### min_chem_eqn_scale

```
min_chem_eqn_scale = 1d0
```

### hydro_mtx_max_allowed_{abs}{dlogT | dlogRho | logT | logRho}

Force retry with smaller timestep if hydro solves change T or Rho by too much or make them too large.

```
hydro_mtx_max_allowed_abs_dlogT = 99d0
hydro_mtx_max_allowed_abs_dlogRho = 99d0
min_logT_for_hydro_mtx_max_allowed = -1d99
hydro_mtx_max_allowed_logT = 12d0
hydro_mtx_max_allowed_logRho = 12d0
```

```
hydro_mtx_min_allowed_logT = 1d0
hydro_mtx_min_allowed_logRho = -1d2
```

level 1 of gold tolerances for solver solver

### use_gold_tolerances

### steps_before_use_gold_tolerances

### gold_solver_iters_timestep_limit

### maxT_for_gold_tolerances

### gold_tol_residual_norm1

### gold_iter_for_resid_tol2

### gold_tol_residual_norm2

### gold_tol_max_residual2

### gold_iter_for_resid_tol3

### gold_tol_residual_norm3

### gold_tol_max_residual3

```
use_gold_tolerances = .true.
steps_before_use_gold_tolerances = -1
```

if >= 0, then after this many steps in run, act as if use_gold_tolerances true this allows a delay before turning on gold tolerances NOTE: if using steps_before_use_gold_tolerances >= 0, then set use_gold_tolerances = false

```
maxT_for_gold_tolerances = 1d99
```

```
gold_tol_residual_norm1 = 1d-11
gold_tol_max_residual1 = 1d-9
gold_iter_for_resid_tol2 = 5
gold_tol_residual_norm2 = 1d-8
gold_tol_max_residual2 = 1d-6
gold_iter_for_resid_tol3 = 10
gold_tol_residual_norm3 = 1d-6
gold_tol_max_residual3 = 1d-4
```

```
gold_solver_iters_timestep_limit = 14
```

level 2 of gold tolerances for solver solver - tighter than level 1

### use_gold2_tolerances

### steps_before_use_gold2_tolerances

### gold2_solver_iters_timestep_limit

### gold2_tol_residual_norm1

### gold2_iter_for_resid_tol2

### gold2_tol_residual_norm2

### gold2_tol_max_residual2

### gold2_iter_for_resid_tol3

### gold2_tol_residual_norm3

### gold2_tol_max_residual3

```
use_gold2_tolerances = .false.
steps_before_use_gold2_tolerances = -1
```

if >= 0, then after this many steps in run, act as if use_gold2_tolerances true this allows a delay before turning on level 2 gold tolerances NOTE: if using steps_before_use_gold2_tolerances >= 0, then set use_gold2_tolerances = false

```
gold2_tol_residual_norm1 = 1d-11
gold2_tol_max_residual1 = 1d-9
gold2_iter_for_resid_tol2 = 5
gold2_tol_residual_norm2 = 1d-10
gold2_tol_max_residual2 = 1d-8
gold2_iter_for_resid_tol3 = 10
gold2_tol_residual_norm3 = 1d-8
gold2_tol_max_residual3 = 1d-5
```

```
gold2_solver_iters_timestep_limit = 18
```

### include_rotation_in_total_energy

### previously called include_rotation_in_energy_error_report

```
include_rotation_in_total_energy = .false.
```

artificial viscosity

### use_Pvsc_art_visc

### Pvsc_cq

### Pvsc_zsh

Pvsc is artificial pressure to push back against compression this is the form of artificial viscosity used in RSP if using this, do not set use_artificial_viscosity true.

artificial viscosity controls for the equations see: Appendix C in Stellingwerf 1975 http://adsabs.harvard.edu/abs/1975ApJ…195..441S. In principle, for not too-non-adiabatic convective models artificial viscosity is not needed or should be very small. Hence a large cut-off parameter below (in purely radiative models the default value for cut-off was 0.01)

zsh > 0 delays onset of artificial viscosity can eliminate most/all interior dissipation while still providing for extreme cases. using this parameter the dependence of limiting amplitude on cq is very weak.

```
use_Pvsc_art_visc = .false.
Pvsc_cq = 4.0d0
Pvsc_zsh = 0.1d0
```

### use_artificial_viscosity

use_artificial_viscosity has been replaced by use_Pvsc_art_visc.

## split burn

### op_split_burn

```
op_split_burn = .false.
```

### op_split_burn_min_T

### op_split_burn_min_T_for_variable_T_solver

### op_split_burn_eps

### op_split_burn_odescal

Only do op_split_burn in cells with T >= this limit at start of step.

```
op_split_burn_min_T = 2d9
op_split_burn_min_T_for_variable_T_solver = 1d99
op_split_burn_eps = 1d-5
op_split_burn_odescal = 1d-5
```

### op_split_burn_eps_nuc_infall_limit

turn off `op_split_burn`

nuclear burning if max infall speed exceeds this limit (cm/s).

```
op_split_burn_eps_nuc_infall_limit = 1d99
```

## timestep controls

The terminal output during evolution includes a short string for the `dt_limit`

.
This is to give you some indication of what is limiting the time steps.
Here’s a dictionary mapping those terminal strings to the corresponding control parameters.
(There is a similar table in `mesa/binary/defaults/binary_controls.defaults`

.)

```
terminal output related parameter
'burn steps' burn_steps_limit
'Lnuc' delta_lgL_nuc_limit
'Lnuc_cat' delta_lgL_nuc_cat_limit
'Lnuc_H' delta_lgL_H_limit
'Lnuc_He' delta_lgL_He_limit
'lgL_power_phot' delta_lgL_power_photo_limit
'Lnuc_z' delta_lgL_z_limit
'bad_X_sum' (solver found bad mass sum)
'dL/L' dL_div_L_limit
'dX' dX_limit
'dX/X' dX_div_X_limit
'dX_nuc_drop' dX_nuc_drop_limit
'delta mdot' delta_mdot_limit
'delta total J' delta_lg_total_J_limit
'delta_HR' delta_HR_limit
'delta_mstar' delta_lg_star_mass_limit
'diff iters' diffusion_iters_limit
'diff steps' diffusion_steps_limit
'min_dr_div_cs' dt_div_min_dr_div_cs_limit
'dt_collapse' dt_div_dt_cell_collapse_limit
'eps_nuc_cntr' delta_log_eps_nuc_cntr_limit
'error rate' limit_for_log_rel_rate_in_energy_conservation
'highT del Ye' delta_Ye_highT_limit
'hold' (recent retry, so no increase in dt)
'lgL' delta_lgL_limit
'lgP' delta_lgP_limit
'lgP_cntr' delta_lgP_cntr_limit
'lgR' delta_lgR_limit
'lgRho' delta_lgRho_limit
'lgRho_cntr' delta_lgRho_cntr_limit
'lgT' delta_lgT_limit
'lgT_cntr' delta_lgT_cntr_limit
'lgT_max' delta_lgT_max_limit
'lgT_max_hi_T' delta_lgT_max_at_high_T_limit
'lgTeff' delta_lgTeff_limit
'dX_div_X_cntr' delta_dX_div_X_cntr_limit
'lg_XC_cntr' delta_lg_XC_cntr_limit
'lg_XH_cntr' delta_lg_XH_cntr_limit
'lg_XHe_cntr' delta_lg_XHe_cntr_limit
'lg_XNe_cntr' delta_lg_XNe_cntr_limit
'lg_XO_cntr' delta_lg_XO_cntr_limit
'lg_XSi_cntr' delta_lg_XSi_cntr_limit
'XC_cntr' delta_XC_cntr_limit
'XH_cntr' delta_XH_cntr_limit
'XHe_cntr' delta_XHe_cntr_limit
'XNe_cntr' delta_XNe_cntr_limit
'XO_cntr' delta_XO_cntr_limit
'XSi_cntr' delta_XSi_cntr_limit
'log_eps_nuc' delta_log_eps_nuc_limit
'max_dt' max_years_for_timestep
'neg_mass_frac' (solver found neg mass frac)
'adjust_J_q' adjust_J_q_limit
'solver iters' solver_iters_timestep_limit
'rel_E_err' limit_for_rel_error_in_energy_conservation
'varcontrol' varcontrol_target
'max increase' max_timestep_factor or max_timestep_factor_at_high_T
'max decrease' min_timestep_factor
'retry' (just did a retry)
'b_****' see binary/defaults/binary_controls.defaults
```

### time_delta_coeff

time_delta_coeff - smaller forces smaller timesteps giving better time resolution. multiplier for all real number timestep limits and hard limits. does not apply to integer valued limits such as

solver_iters_timestep_limit

burn_steps_limit

diffusion_steps_limit

diffusion_iters_limit

does not apply to varcontrol_target. analogous to mesh_delta_coeff for better spatial resolution.

```
time_delta_coeff = 1d0
```

### max_timestep

In seconds. `max_timestep <= 0`

means no upper limit.

```
max_timestep = 0
```

### max_years_for_timestep

`max_years_for_timestep <= 0`

means no upper limit.
Note: `max_timestep`

is the control that is used by most of the code.
`max_years_for_timestep`

is just provided as a convenience.
At the start of each step, the evolve routine checks to see if `max_years_for_timestep > 0`

,
and if so, it sets `max_timestep = max_years_for_timestep*secyer`

.

```
max_years_for_timestep = 0
```

### max_timestep_hi_T_limit

If `max T >= this`

, then switch to `hi_T_max_years_for_timestep`

.
Ignore if <= 0.

```
max_timestep_hi_T_limit = -1
```

### hi_T_max_years_for_timestep

Max years for timestep if `max_timestep_hi_T_limit`

is active.

```
hi_T_max_years_for_timestep = 0
```

### min_timestep_factor

Lower limit for ratio of new timestep to previous timestep. i.e., allow dt to get smaller by no more than this factor – 0 means no limit.

```
min_timestep_factor = 0.8d0
```

### force_timestep

In seconds. `force_timestep <= 0`

means no forced timestep.

```
force_timestep = 0
```

### force_timestep_years

Note: `force_timestep`

is the control that is used by most of the code.
`force_timestep_years`

is just provided as a convenience.
At the start of each step, the evolve routine checks if `force_timestep_years > 0`

,
and if so, it sets `force_timestep = force_timestep_years*secyer`

.

```
force_timestep_years = 0
```

### force_timestep_min

In seconds. `force_timestep_min <= 0`

means no forced lower limit.

```
force_timestep_min = 0
```

### force_timestep_min_years

Note: `force_timestep_min`

is the control that is used by most of the code.
`force_timestep_min_years`

is just provided as a convenience.
At the start of each step, the evolve routine checks if `force_timestep_min_years > 0`

,
and if so, it sets `force_timestep_min = force_timestep_min_years*secyer`

.

```
force_timestep_min_years = 0
```

### force_timestep_min_factor

If dt is < `force_timestep_min`

, then
replace dt by `min(dt*force_timestep_min_factor, force_timestep_min)`

```
force_timestep_min_factor = 2d0
```

### max_timestep_factor

### max_timestep_factor_at_high_T

### min_logT_for_max_timestep_factor_at_high_T

Upper limit for ratio of new timestep to previous timestep.
i.e., allow dt to get larger by no more than this factor – 0 means no limit.
use `max_timestep_factor_at_high_T`

when max logT > `min_logT_for_max_timestep_factor_at_high_T`

.

```
max_timestep_factor = 1.2d0
max_timestep_factor_at_high_T = 1.1d0
min_logT_for_max_timestep_factor_at_high_T = 1d99
```

### timestep_factor_for_retries

Before retry, decrease dt by this.

```
timestep_factor_for_retries = 0.5d0
```

### retry_hold

No increases in timestep for `retry_hold`

steps after a retry.

```
retry_hold = 1
```

### neg_mass_fraction_hold

No increases in timestep for `neg_mass_fraction_hold`

steps after
a retry caused by a negative mass fraction.

```
neg_mass_fraction_hold = 2
```

### timestep_dt_factor = 0.9

dt reduction factor exceed timestep limits.

```
timestep_dt_factor = 0.9d0
```

### use_dt_low_pass_controller

Enable low pass filter for smoother timestep variations.

```
use_dt_low_pass_controller = .true.
```

### varcontrol_target

This is the target value for relative variation in the structure from one model to the next. The default timestep adjustment is to increase or reduce the timestep depending on whether the actual variation was smaller or greater than this value.

```
varcontrol_target = 1d-3
```

### min_allowed_varcontrol_target

The run will terminate if varcontrol_target < min_allowed_varcontrol_target It is not usually a good idea to reduce this. Instead, use time_delta_coeff to do time resolution convergence studies.

```
min_allowed_varcontrol_target = 1d-4
```

### varcontrol_dt_limit_ratio_hard_max

`varcontrol_dt_limit_ratio`

is the actual varcontrol value divided by the target.
if that ratio exceeds this limit, then retry with a smaller timestep.
this let’s you prevent large changes from happening in a single step.

```
varcontrol_dt_limit_ratio_hard_max = 1d99
```

### never_skip_hard_limits

If true, then don’t skip hard limits even immediately after a retry.

```
never_skip_hard_limits = .true.
```

### relax_hard_limits_after_retry

If true, then don’t enforce hard limits immediately after a retry.

```
relax_hard_limits_after_retry = .false.
```

limits based on iterations required by various solvers

### solver_iters_timestep_limit

If solver solve uses more `solver_iterations`

than this, reduce the next timestep.
NOTE: when using gold tolerances, set gold_solver_iters_timestep_limit.

```
solver_iters_timestep_limit = 7
```

### burn_steps_limit

If burn solver uses more steps than this, reduce the next timestep.

```
burn_steps_limit = 10000
```

### burn_steps_hard_limit

If burn solver uses more steps than this, retry.

```
burn_steps_hard_limit = 20000
```

### diffusion_steps_limit

If diffusion solver uses more steps than this, reduce the next timestep.

```
diffusion_steps_limit = 500
```

### diffusion_steps_hard_limit

If diffusion solver uses more steps than this, retry.

```
diffusion_steps_hard_limit = 700
```

### diffusion_iters_limit

If use a total number of iters > this, reduce the next timestep.

```
diffusion_iters_limit = 600
```

### diffusion_iters_hard_limit

If use a total number of iters > this, retry.

```
diffusion_iters_hard_limit = 800
```

limits based on max decrease in mass fraction at any location in star

### dX_mix_dist_limit

Option to ignore decreases in abundance in non-mixed cells near mixing boundaries.
Ignore abundance changes if nearest mixing boundary is closer than this in Msun units.
This applies to `dX`

, and `dX_div_X`

limits.

```
dX_mix_dist_limit = 1d-4
```

Limit on magnitude of decrease in any cell hydrogen abundance during a single timestep.
dH here is `abs(xa(j,k) - xa_old(j,k))`

for any cell k and all species j, eg ‘h1’, ‘he4’, etc.
special ‘species’ X (any hydrogen), Y (any helium) and Z (any metals) are
allowed here. E.g. ‘Z’ will trigger the timestep control if any metal isotope
abundance individually satisfies the conditions below.
Considers all cells except where have convective mixing.

dX_limit_species(1) = ‘h1’ dX_limit_species(2) = ‘he4’ dX_limit_species(3:) = ‘’

### dX_limit_min_X

dX limits only apply where xa(j,k) >= this limit.

```
dX_limit_min_X(:) = 1d99
```

### dX_limit

If max dX is greater than this,
reduce the next timestep by `dX_limit`

/`max_dX`

.

```
dX_limit(:) = 1d99
```

### dX_hard_limit

If max dX is greater than this, retry with smaller timestep.

```
dX_hard_limit(:) = 1d99
```

### dX_decreases_only

If true, then only consider decreases in abundance.
`dX_decreases_only`

applies to `dX_div_X`

also.

```
dX_decreases_only(:) = .true.
```

Limit on magnitude of relative decrease in any cell abundance.
`dX_div_X`

here is abs(xa(j,k) - xa_old(j,k))/xa(j,k)
for any cell k and any species j.
Considers all cells except where have convective mixing.

### dX_div_X_limit_min_X

`dX_div_X`

limits only apply where xa(j,k) >= this limit.

```
dX_div_X_limit_min_X(1) = 1d-3
dX_div_X_limit_min_X(2) = 1d-3
dX_div_X_limit_min_X(3:) = 1d99
```

### dX_div_X_limit

If max `dX_div_X`

is greater than this,
reduce the next timestep by `dX_limit/max_dX`

.

```
dX_div_X_limit(1) = 0.9d0
dX_div_X_limit(2) = 0.9d0
dX_div_X_limit(3:) = 1d99
```

### dX_div_X_hard_limit

If max `dX_div_X`

is greater than this, retry with smaller timestep.

```
dX_div_X_hard_limit(:) = 1d99
```

### dX_div_X_at_high_T_limit

### dX_div_X_at_high_T_hard_limit

### dX_div_X_at_high_T_limit_lgT_min

```
dX_div_X_at_high_T_limit(:) = 1d99
dX_div_X_at_high_T_hard_limit(:) = 1d99
dX_div_X_at_high_T_limit_lgT_min(:) = 1d99
```

Limits on max drop in abundance mass fraction from burning with possible mixing inflow. This considers both nuclear reactions and offsetting effect of mixing inflow.

### dX_nuc_drop_min_X_limit

`dX_nuc_drop_limit`

only for `X > dX_nuc_drop_min_X_limit`

.
note that this is the abundance ot the species, not the H1 abundance for the cell.
i.e., if species abundance is below this limit, then ignore it for the dX_nuc_drop limit.

```
dX_nuc_drop_min_X_limit = 1d-4
```

### dX_nuc_drop_max_A_limit

`dX_nuc_drop_limit`

only for species with `A <= dX_nuc_drop_max_A_limit`

.

```
dX_nuc_drop_max_A_limit = 52
```

### dX_nuc_drop_limit_at_high_T

Negative means use value for `dX_nuc_drop_limit`

,
else use this limit when max logT > 9.45.

```
dX_nuc_drop_limit_at_high_T = -1
```

### dX_nuc_drop_limit

If max `dX_nuc_drop`

is greater than `dX_nuc_drop_limit`

,
reduce the next timestep by `dX_nuc_drop_limit`

/`max_dX_nuc_drop`

.

```
dX_nuc_drop_limit = 5d-2
```

### dX_nuc_drop_hard_limit

If max `dX_nuc_drop`

is greater than `dX_nuc_drop_hard_limit`

,
retry with smaller timestep.

```
dX_nuc_drop_hard_limit = 1d99
```

### dX_nuc_drop_min_yrs_for_dt

Don’t let `dX_nuc_drop`

change dt to smaller than this.

```
dX_nuc_drop_min_yrs_for_dt = 1d-9
```

#### limits based on relative changes in variables L, P, Rho, T, R, eps_nuc

limit on magnitude of relative change in L at any grid point

```
dL_div_L = abs(L(k) - L_old(k))/L(k)
```

### dL_div_L_limit

If max abs `dL_div_L`

is greater than this, reduce the next timestep.

```
dL_div_L_limit = -1
```

### dL_div_L_hard_limit

If max abs `dL_div_L`

is greater than this, retry with smaller timestep.

```
dL_div_L_hard_limit = -1
```

### dL_div_L_limit_min_L

In Lsun units.
`dL_div_L`

limits only apply where `L(k) >= Lsun*dL_limit_min_L`

```
dL_div_L_limit_min_L = 1d99
```

### delta_lgP_limit

Limit for magnitude of max change in log10 total pressure in any cell.

```
delta_lgP_limit = 1
```

### delta_lgP_hard_limit

If max `delta_lgP`

is greater than `delta_lgP_hard_limit`

,
retry with smaller timestep.

```
delta_lgP_hard_limit = -1
```

### delta_lgP_limit_min_lgP

`delta_lgP_limit`

limits only apply where `log10_P(k) >= delta_lgP_limit_min_lgP`

```
delta_lgP_limit_min_lgP = 1d99
```

### delta_lgRho_limit

Limit for magnitude of max change in log10 density in any cell.

```
delta_lgRho_limit = 1
```

### delta_lgRho_hard_limit = -1

If max `delta_lgRho`

is greater than `delta_lgRho_hard_limit`

,
retry with smaller timestep.

```
delta_lgRho_hard_limit = -1
```

### delta_lgRho_limit_min_lgRho

`delta_lgRho_limit`

limits only apply where `log10_Rho(k) >= delta_lgRho_limit_min_lgRho`

.

```
delta_lgRho_limit_min_lgRho = 1d99
```

### delta_lgT_limit

Limit for magnitude of max change in log10 temperature in any cell.

```
delta_lgT_limit = 0.5d0
```

### delta_lgT_hard_limit

If max `delta_lgT`

is greater than `delta_lgT_hard_limit`

,
retry with smaller timestep.

```
delta_lgT_hard_limit = -1
```

### delta_lgT_limit_min_lgT

`delta_lgT_limit`

limits only apply where `log10_T(k) >= delta_lgT_limit_min_lgT`

.

```
delta_lgT_limit_min_lgT = 1d99
```

### delta_lgE_limit

Limit for magnitude of max change in log10 internal energy in any cell.

```
delta_lgE_limit = 0.1d0
```

### delta_lgE_hard_limit

If max `delta_lgE`

is greater than `delta_lgE_hard_limit`

,
retry with smaller timestep.

```
delta_lgE_hard_limit = -1
```

### delta_lgE_limit_min_lgE

`delta_lgE_limit`

limits only apply where `log10(E(k)) >= delta_lgE_limit_min_lgE`

.

```
delta_lgE_limit_min_lgE = 1d99
```

### delta_lgR_limit

Limit for magnitude of max change in log10 radius at any cell boundary.

```
delta_lgR_limit = 0.5d0
```

### delta_lgR_hard_limit

If max `delta_lgR`

is greater than `delta_lgR_hard_limit`

,
retry with smaller timestep.

```
delta_lgR_hard_limit = -1
```

### delta_lgR_limit_min_lgR

`delta_lgR_limit`

limits only apply where `log10_R(k) >= delta_lgR_limit_min_lgR`

.

```
delta_lgR_limit_min_lgR = 1d99
```

### delta_Ye_highT_limit

Limit for magnitude of max change in Ye in high T cells.

```
delta_Ye_highT_limit = 99
```

Limit testing for max `delta_ye`

to cells with `T >= minT_for_highT_Ye_limit`

If this high T max `delta_Ye`

is greater than `delta_Ye_highT_limit`

,
reduce the next timestep by `delta_Ye_highT_limit`

/`max_delta_Ye`

.

```
delta_Ye_highT_hard_limit = -1
```

### minT_for_highT_Ye_limit

Limit testing for max `delta_ye`

to cells with `T >= minT_for_highT_Ye_limit`

.
If this high T max `delta_Ye`

is greater than `delta_Ye_highT_limit`

,
retry with smaller timestep.

```
minT_for_highT_Ye_limit = 7d9
```

### delta_log_eps_nuc_limit

Limit for magnitude of max change in log10 `eps_nuc`

in any cell.
Only applies to increases in non-convective zones.

```
delta_log_eps_nuc_limit = -1
```

### delta_log_eps_nuc_hard_limit

If max `delta_log_eps_nuc`

is greater than `delta_log_eps_nuc_hard_limit`

,
retry with smaller timestep.

```
delta_log_eps_nuc_hard_limit = -1
```

#### limits based on integrated power at each point for each category of nuclear reaction

`lgL_nuc_cat`

= nuclear reaction energy release for a particular category of reaction (Lsun units).
Energy release here excludes neutrinos.

### delta_lgL_nuc_cat_limit

Limit for magnitude of change in `lgL_nuc`

for category.

```
delta_lgL_nuc_cat_limit = -1
```

### delta_lgL_nuc_cat_hard_limit

If max delta is greater than `delta_lgL_nuc_cat_hard_limit`

,
retry with smaller timestep.

```
delta_lgL_nuc_cat_hard_limit = -1
```

### lgL_nuc_cat_burn_min

Ignore changes in `lgL_nuc`

for category if value is less than this.

```
lgL_nuc_cat_burn_min = -1
```

### lgL_nuc_mix_dist_limit

Ignore if nearest boundary is closer than this. Ignore changes in lgL in cells near mixing boundaries.

```
lgL_nuc_mix_dist_limit = 1d-6
```

`L_H_burn`

= integrated power at surface from PP and CNO (in Lsun units)

values for `lgL_H`

are `log10(max(1, L_H_burn))`

### delta_lgL_H_limit

limit for magnitude of change in `lgL_H`

```
delta_lgL_H_limit = -1
```

### delta_lgL_H_hard_limit

if max delta is greater than `delta_lgL_H_hard_limit`

,
retry with smaller timestep

```
delta_lgL_H_hard_limit = -1
```

### lgL_H_burn_min

ignore changes in `lgL_H`

if value is less than this

```
lgL_H_burn_min = 1.5d0
```

### lgL_H_drop_factor

when `L_H`

is dropping, multiply limits by this factor

```
lgL_H_drop_factor = 1
```

### lgL_H_burn_relative_limit

ignore changes in `lgL_H`

if `max(lgL_He,lgL_z) - lgL_H > this`

```
lgL_H_burn_relative_limit = 3
```

`L_He_burn`

= integrated power at surface from triple alpha (in Lsun units)

values for `lgL_He`

are `log10(max(1, L_He_burn))`

### delta_lgL_He_limit

Limit for magnitude of change in lgL_He.

```
delta_lgL_He_limit = 0.025d0
```

### delta_lgL_He_hard_limit

If max delta is greater than `delta_lgL_He_hard_limit`

,
retry with smaller timestep.

```
delta_lgL_He_hard_limit = -1
```

### lgL_He_burn_min

Ignore changes in `lgL_He`

if value is less than this.

```
lgL_He_burn_min = 2.5d0
```

### lgL_He_drop_factor

When `L_He`

is dropping, multiply limits by this factor.

```
lgL_He_drop_factor = 1
```

### lgL_He_burn_relative_limit

Ignore changes in `lgL_He`

if `max(lgL_H,lgL_z) - lgL_He > this`

.

```
lgL_He_burn_relative_limit = 3
```

`L_z_burn`

= integrated power at surface from nuclear burning other than H, He, or C (in Lsun units)
excluding photodistintegrations

values for `lgL_z`

are `log10(max(1, L_z_burn))`

### delta_lgL_z_limit

Limit for magnitude of change in `lgL_z`

.

```
delta_lgL_z_limit = -1
```

### delta_lgL_z_hard_limit

If max delta is greater than `delta_lgL_z_hard_limit`

,
retry with smaller timestep.

```
delta_lgL_z_hard_limit = -1
```

### lgL_z_burn_min

Ignore changes in `lgL_z`

if value is less than this.

```
lgL_z_burn_min = 2.5d0
```

### lgL_z_drop_factor

When `L_z`

is dropping, multiply limits by this factor.

```
lgL_z_drop_factor = 1
```

### lgL_z_burn_relative_limit

Ignore changes in `lgL_z`

if `max(lgL_H,lgL_He) - lgL_z > this`

.

```
lgL_z_burn_relative_limit = 3
```

#### limits based on total integrated power at surface for all nuclear reactions

excluding photodistintegrations

`L_nuc`

= nuclear reaction total energy release for all nuclear reactions (Lsun units)

### delta_lgL_nuc_limit

### delta_lgL_nuc_hard_limit

### delta_lgL_nuc_at_high_T_limit

### delta_lgL_nuc_at_high_T_hard_limit

### delta_lgL_nuc_at_high_T_limit_lgT_min

### max_lgT_for_lgL_nuc_limit

When `L_nuc`

is dropping, multiply limits by `lgL_nuc_drop_factor`

.

ignore changes in `lgL_nuc`

if max logT > `max_lgT_for_lgL_nuc_limit`

.

limit for magnitude of change in `lgL_nuc`

retry if max delta is greater than `delta_lgL_nuc_hard_limit`

,
ignore changes in `lgL_nuc`

if value is less than `lgL_nuc_burn_min`

- if max logT is >
`delta_lgL_nuc_at_high_T_limit_lgT_min`

then use

`delta_lgL_nuc_at_high_T_limit`

and`delta_lgL_nuc_at_high_T_hard_limit`

- else
use

`delta_lgL_nuc_limit`

and`delta_lgL_nuc_hard_limit`

at extreme temperatures, can have numerical jitters in this as a result of almost cancelling large positive and negative contributions of forward and reverse rates such as photodisintegration and rebuilding of he4 so if doing advanced burning, may want to turn off lgL_nuc limits above some max logT and turn on lgL_power_photo limits at a somewhat smaller max logT.

```
delta_lgL_nuc_limit = -1
delta_lgL_nuc_hard_limit = -1
```

```
delta_lgL_nuc_at_high_T_limit = -1
delta_lgL_nuc_at_high_T_hard_limit = -1
delta_lgL_nuc_at_high_T_limit_lgT_min = 1d99
```

```
max_lgT_for_lgL_nuc_limit = 1d99
lgL_nuc_burn_min = 0.5d0
lgL_nuc_drop_factor = 10
```

#### limits based on total integrated power at surface for photodistintegrations

`L_photo`

= nuclear reaction total energy release for all photodistintegrations (Lsun units)
note that photodistintegrations consume energy so the total released is negative.
photodisintegrations become large during late burning at high temperatures.
values for `lgL_photo`

are based on `L_by_category(iphoto)`

### delta_lgL_power_photo_limit

### delta_lgL_power_photo_hard_limit

### min_lgT_for_lgL_power_photo_limit

### lgL_power_photo_burn_min

### lgL_power_photo_drop_factor

Limit for magnitude of change in `lgL_photo`

.
If max delta is greater than `delta_lgL_power_photo_hard_limit`

,
retry with smaller timestep.
ignore delta_lgL_power_photo_limit when max logT < `min_lgT_for_lgL_power_photo_limit`

.
Ignore changes in `lgL_photo`

if value is less than `lgL_power_photo_burn_min`

.
When `L_photo`

is dropping, multiply limits by `lgL_power_photo_drop_factor`

.

```
delta_lgL_power_photo_limit = -1
delta_lgL_power_photo_hard_limit = -1
min_lgT_for_lgL_power_photo_limit = 9d0
lgL_power_photo_burn_min = 10d0
lgL_power_photo_drop_factor = 10
```

limits based on changes at photosphere

### delta_lgTeff_limit

### delta_lgTeff_hard_limit

Limit for magnitude of max change in log10 temperature at photosphere.

```
delta_lgTeff_limit = 0.01d0
delta_lgTeff_hard_limit = -1
```

### delta_lgL_limit_L_min

### delta_lgL_limit

### delta_lgL_hard_limit

Limit for magnitude of change in log10(L_surf/Lsun).
Only apply this limit when `L_surf`

>= `delta_lgL_limit_L_min`

(in Lsun units).

```
delta_lgL_limit_L_min = -100
delta_lgL_limit = 0.1d0
delta_lgL_hard_limit = -1
```

### dt_div_min_dr_div_cs_limit

### dt_div_min_dr_div_cs_hard_limit

limit for dt compared to explicit solver timescale (negative means no limit)

```
min_dr_div_cs = min over all cells of dr/csound (seconds)
```

```
dt_div_min_dr_div_cs_limit = -1
dt_div_min_dr_div_cs_hard_limit = -1
```

### dt_div_dt_cell_collapse_limit

### dt_div_dt_cell_collapse_hard_limit

limit for dt compared to cell_collapse timescale (negative means no limit)

```
dt_cell_collapse = min over shells k that have v(k+1) > v(k) of
(r(k)-r(k+1))/(v(k+1)-v(k)), the time for the cell to collapse
to zero thickness at current velocities. only for v_flag true.
```

```
dt_div_dt_cell_collapse_limit = -1
dt_div_dt_cell_collapse_hard_limit = -1
```

### min_k_for_dt_div_min_dr_div_cs_limit

### min_q_for_dt_div_min_dr_div_cs_limit

### max_q_for_dt_div_min_dr_div_cs_limit

### check_remnant_only_for_dt_div_min_dr_div_cs_limit

```
min_k_for_dt_div_min_dr_div_cs_limit = 20
min_q_for_dt_div_min_dr_div_cs_limit = 0.005d0
max_q_for_dt_div_min_dr_div_cs_limit = 0.995d0
check_remnant_only_for_dt_div_min_dr_div_cs_limit = .false.
```

### min_abs_du_div_cs_for_dt_div_min_dr_div_cs_limit

### min_abs_u_div_cs_for_dt_div_min_dr_div_cs_limit

only use `dt_div_min_dr_div_cs_limit`

at cells where
`abs_du_div_cs`

> `min_abs_du_div_cs_for_dt_div_min_dr_div_cs_limit`

and
and
`abs_u_div_cs`

> `min_abs_u_div_cs_for_dt_div_min_dr_div_cs_limit`

allow focus on regions near shock face.

```
min_abs_u_div_cs_for_dt_div_min_dr_div_cs_limit = 0.8d0
min_abs_du_div_cs_for_dt_div_min_dr_div_cs_limit = 0.01d0
```

limits based on changes in location on HR diagram

### delta_HR_ds_L

### delta_HR_ds_Teff

```
dlgL = log10(L/L_prev)
dlgTeff = log10(Teff/Teff_prev)
```

```
delta_HR_ds_L = 1
delta_HR_ds_Teff = 1
```

### delta_HR_limit

### delta_HR_hard_limit

limit for dHR (negative means no limit)

```
dHR = sqrt((delta_HR_ds_L*dlgL)**2 + (delta_HR_ds_Teff*dlgTeff)**2)
```

```
delta_HR_limit = -1
delta_HR_hard_limit = -1
```

### delta_lgT_max_limit

### delta_lgT_max_hard_limit

### delta_lgT_max_limit_lgT_min

### delta_lgT_max_at_high_T_limit

### delta_lgT_max_at_high_T_hard_limit

### delta_lgT_max_at_high_T_limit_lgT_min

### delta_lgT_max_limit_only_after_near_zams

limit for magnitude of change in max over all cells of log10 T
this is for off center flashes in degenerate material (e.g., He or Ne)
Only apply this limit when `lgT_max`

>= `delta_lgT_max_limit_lgT_min`

.

similarly, use `at_high_T`

limits only
when `lgT_max`

>= `delta_lgT_max_at_high_T_limit_lgT_min`

.
this can be useful since higher order temperature sensitivity of rates at high T
may require smaller limits for changes.

```
delta_lgT_max_limit = -1
delta_lgT_max_hard_limit = -1
delta_lgT_max_limit_lgT_min = 9d0
```

```
delta_lgT_max_at_high_T_limit = -1
delta_lgT_max_at_high_T_hard_limit = -1
delta_lgT_max_at_high_T_limit_lgT_min = -1
```

```
delta_lgT_max_limit_only_after_near_zams = .false.
```

limits based on changes at center

### delta_lgT_cntr_limit

### delta_lgT_cntr_hard_limit

### delta_lgT_cntr_limit_only_after_near_zams

limit for magnitude of change in log10 temperature at center

```
delta_lgT_cntr_limit = 0.01d0
delta_lgT_cntr_hard_limit = -1
delta_lgT_cntr_limit_only_after_near_zams = .true.
```

### delta_lgP_cntr_limit

### delta_lgP_cntr_hard_limit

limit for magnitude of change in log10 pressure at center

```
delta_lgP_cntr_limit = -1
delta_lgP_cntr_hard_limit = -1
```

### delta_lgRho_cntr_limit

### delta_lgRho_cntr_hard_limit

limit for magnitude of change in log10 density at center

```
delta_lgRho_cntr_limit = 0.05d0
delta_lgRho_cntr_hard_limit = -1
```

`dX_div_X_cntr`

is max(abs(xa(j,nz)-xa_old(j,nz))/xa(j,nz)) for any species j
Small timesteps as the center carbon is exhausted.

### delta_dX_div_X_cntr_min

Ignore changes in `dX_div_X_cntr`

if value is less than this.

```
delta_dX_div_X_cntr_min = -5
```

### delta_dX_div_X_cntr_max

Ignore changes in `dX_div_X_cntr`

if value is more than this.

```
delta_dX_div_X_cntr_max = 0
```

### delta_dX_div_X_cntr_limit

If max delta is greater than `delta_dX_div_X_cntr_limit`

,
reduce the next timestep by `delta_dX_div_X_cntr_limit`

/`max_delta`

.

```
delta_dX_div_X_cntr_limit = 0.1d0
```

### delta_dX_div_X_cntr_hard_limit

If max delta is greater than `delta_dX_div_X_cntr_hard_limit`

,
retry with smaller timestep.

```
delta_dX_div_X_cntr_hard_limit = -1
```

`lg_XH_cntr`

is log10(h1 mass fraction at center).
Small timesteps as the center hydrogen is exhausted.

### delta_lg_XH_cntr_min

Ignore changes in `lg_XH_cntr`

if value is less than this.

```
delta_lg_XH_cntr_min = -6
```

### delta_lg_XH_cntr_max

Ignore changes in `lg_XH_cntr`

if value is more than this.

```
delta_lg_XH_cntr_max = 0
```

### delta_lg_XH_cntr_limit

If max delta is greater than this,
reduce the next timestep by `delta_lg_XH_cntr_limit`

/`max_delta`

.

```
delta_lg_XH_cntr_limit = 0.05d0
```

### delta_lg_XH_cntr_hard_limit

If max delta is greater than `delta_lg_XH_cntr_hard_limit`

,
retry with smaller timestep.

```
delta_lg_XH_cntr_hard_limit = -1
```

`lg_XHe_cntr`

is log10(he4 mass fraction at center)
small timesteps as the center helium is exhausted.

### delta_lg_XHe_cntr_min

Ignore changes in `lg_XHe_cntr`

if value is less than this.

```
delta_lg_XHe_cntr_min = -6
```

### delta_lg_XHe_cntr_max

Ignore changes in `lg_XHe_cntr`

if value is more than this.

```
delta_lg_XHe_cntr_max = 0
```

### delta_lg_XHe_cntr_limit

If max delta is greater than `delta_lg_XHe_cntr_limit`

,
reduce the next timestep by `delta_lg_XHe_cntr_limit`

/`max_delta`

.

```
delta_lg_XHe_cntr_limit = 0.1d0
```

### delta_lg_XHe_cntr_hard_limit

If max delta is greater than `delta_lg_XHe_cntr_hard_limit`

,
retry with smaller timestep.

```
delta_lg_XHe_cntr_hard_limit = -1
```

`lg_XC_cntr`

is log10(c12 mass fraction at center).
Small timesteps as the center carbon is exhausted.

### delta_lg_XC_cntr_min

Ignore changes in `lg_XC_cntr`

if value is less than this.

```
delta_lg_XC_cntr_min = -5
```

### delta_lg_XC_cntr_max

Ignore changes in `lg_XC_cntr`

if value is more than this.

```
delta_lg_XC_cntr_max = 0
```

### delta_lg_XC_cntr_limit

If max delta is greater than `delta_lg_XC_cntr_limit`

,
reduce the next timestep by `delta_lg_XC_cntr_limit`

/`max_delta`

.

```
delta_lg_XC_cntr_limit = 0.1d0
```

### delta_lg_XC_cntr_hard_limit

If max delta is greater than `delta_lg_XC_cntr_hard_limit`

,
retry with smaller timestep.

```
delta_lg_XC_cntr_hard_limit = -1
```

`lg_XO_cntr`

is log10(o16 mass fraction at center)
Small timesteps as the center oxygen is exhausted.

### delta_lg_XNe_cntr_min

Ignore changes in `lg_XNe_cntr`

if value is less than this.

```
delta_lg_XNe_cntr_min = -5
```

### delta_lg_XNe_cntr_max

Ignore changes in `lg_XNe_cntr`

if value is more than this.

```
delta_lg_XNe_cntr_max = 0
```

### delta_lg_XNe_cntr_limit

If max delta is greater than `delta_lg_XNe_cntr_limit`

,
reduce the next timestep by `delta_lg_XNe_cntr_limit`

/`max_delta`

.

```
delta_lg_XNe_cntr_limit = 1d99
```

### delta_lg_XNe_cntr_hard_limit

If max delta is greater than `delta_lg_XNe_cntr_hard_limit`

,
retry with smaller timestep.

```
delta_lg_XNe_cntr_hard_limit = -1
```

### delta_lg_XO_cntr_min

Ignore changes in `lg_XO_cntr`

if value is less than this.

```
delta_lg_XO_cntr_min = -5
```

### delta_lg_XO_cntr_max

Ignore changes in `lg_XO_cntr`

if value is more than this.

```
delta_lg_XO_cntr_max = 0
```

### delta_lg_XO_cntr_limit

If max delta is greater than `delta_lg_XO_cntr_limit`

,
reduce the next timestep by `delta_lg_XO_cntr_limit`

/`max_delta`

.

```
delta_lg_XO_cntr_limit = 1d99
```

### delta_lg_XO_cntr_hard_limit

If max delta is greater than `delta_lg_XO_cntr_hard_limit`

,
retry with smaller timestep.

```
delta_lg_XO_cntr_hard_limit = -1
```

### delta_lg_XSi_cntr_min

Ignore changes in `lg_XSi_cntr`

if value is less than this.

```
delta_lg_XSi_cntr_min = -5
```

### delta_lg_XSi_cntr_max

Ignore changes in `lg_XSi_cntr`

if value is more than this.

```
delta_lg_XSi_cntr_max = 0
```

### delta_lg_XSi_cntr_limit

If max delta is greater than `delta_lg_XSi_cntr_limit`

,
reduce the next timestep by `delta_lg_XSi_cntr_limit`

/`max_delta`

.

```
delta_lg_XSi_cntr_limit = 1d99
```

### delta_lg_XSi_cntr_hard_limit

If max delta is greater than `delta_lg_XSi_cntr_hard_limit`

,
retry with smaller timestep.

```
delta_lg_XSi_cntr_hard_limit = -1
```

### delta_XH_cntr_limit

If max delta is greater than this,
reduce the next timestep by `delta_XH_cntr_limit`

/`max_delta`

.

```
delta_XH_cntr_limit = 0.01d0
```

### delta_XH_cntr_hard_limit

If max delta is greater than `delta_XH_cntr_hard_limit`

,
retry with smaller timestep.

```
delta_XH_cntr_hard_limit = -1
```

### delta_XHe_cntr_limit

If max delta is greater than `delta_XHe_cntr_limit`

,
reduce the next timestep by `delta_XHe_cntr_limit`

/`max_delta`

.

```
delta_XHe_cntr_limit = 0.01d0
```

### delta_XHe_cntr_hard_limit

If max delta is greater than `delta_XHe_cntr_hard_limit`

,
retry with smaller timestep.

```
delta_XHe_cntr_hard_limit = -1
```

### delta_XC_cntr_limit

If max delta is greater than `delta_XC_cntr_limit`

,
reduce the next timestep by `delta_XC_cntr_limit`

/`max_delta`

.

```
delta_XC_cntr_limit = 0.01d0
```

### delta_XC_cntr_hard_limit

If max delta is greater than `delta_XC_cntr_hard_limit`

,
retry with smaller timestep.

```
delta_XC_cntr_hard_limit = -1
```

### delta_XNe_cntr_limit

If max delta is greater than `delta_XNe_cntr_limit`

,
reduce the next timestep by `delta_XNe_cntr_limit`

/`max_delta`

.

```
delta_XNe_cntr_limit = 0.01d0
```

### delta_XNe_cntr_hard_limit

If max delta is greater than `delta_XNe_cntr_hard_limit`

,
retry with smaller timestep.

```
delta_XNe_cntr_hard_limit = -1
```

### delta_XO_cntr_limit

If max delta is greater than `delta_XO_cntr_limit`

,
reduce the next timestep by `delta_XO_cntr_limit`

/`max_delta`

.

```
delta_XO_cntr_limit = 0.01d0
```

### delta_XO_cntr_hard_limit

If max delta is greater than `delta_XO_cntr_hard_limit`

,
retry with smaller timestep.

```
delta_XO_cntr_hard_limit = -1
```

### delta_XSi_cntr_limit

If max delta is greater than `delta_XSi_cntr_limit`

,
reduce the next timestep by `delta_XSi_cntr_limit`

/`max_delta`

.

```
delta_XSi_cntr_limit = 0.01d0
```

### delta_XSi_cntr_hard_limit

If max delta is greater than `delta_XSi_cntr_hard_limit`

,
retry with smaller timestep.

```
delta_XSi_cntr_hard_limit = -1
```

### delta_dX_div_X_drop_only

### delta_lg_XH_drop_only

### delta_lg_XHe_drop_only

### delta_lg_XC_drop_only

### delta_lg_XNe_drop_only

### delta_lg_XO_drop_only

### delta_lg_XSi_drop_only

### delta_XH_drop_only

### delta_XHe_drop_only

### delta_XC_drop_only

### delta_XNe_drop_only

### delta_XO_drop_only

### delta_XSi_drop_only

If true, then only limit drops in abundance.

```
delta_dX_div_X_drop_only = .false.
delta_lg_XH_drop_only = .false.
delta_lg_XHe_drop_only = .false.
delta_lg_XC_drop_only = .false.
delta_lg_XNe_drop_only = .false.
delta_lg_XO_drop_only = .false.
delta_lg_XSi_drop_only = .false.
delta_XH_drop_only = .false.
delta_XHe_drop_only = .false.
delta_XC_drop_only = .false.
delta_XNe_drop_only = .false.
delta_XO_drop_only = .false.
delta_XSi_drop_only = .false.
```

#### limits based on changes in mass of the star

### delta_lg_star_mass_limit

### delta_lg_star_mass_hard_limit

Limit for magnitude of change in log10(M/Msun).

```
delta_lg_star_mass_limit = 5d-3
delta_lg_star_mass_hard_limit = -1
```

limit for change in mdot in Msun/yr
+ `delta_mdot_atol`

tolerance for absolute changes
+ `delta_mdot_rtol`

tolerance for relative changes

```
delta_mdot_atol = 1d-3
delta_mdot_rtol = 0.5d0
```

### delta_mdot_limit

### delta_mdot_hard_limit

```
delta_mot = abs(mdot - mdot_old)/ (delta_mdot_atol*Msun/secyer + &
delta_mdot_rtol*max(abs(mdot),abs(mdot_old)))
```

ignore if < 0

```
delta_mdot_limit = -1
delta_mdot_hard_limit = -1
```

### adjust_J_q_limit

### adjust_J_q_hard_limit

limit for mass coordinate down to which angular momentum is adjusted when using do_adjust_J_lost

```
adjust_J_q_limit = 0.99
adjust_J_q_hard_limit = 0.98
```

### limit_for_rel_error_in_energy_conservation

### hard_limit_for_rel_error_in_energy_conservation

```
rel_error_in_energy_conservation = abs(error_in_energy_conservation/total_energy)
```

```
limit_for_rel_error_in_energy_conservation = 1d-4
hard_limit_for_rel_error_in_energy_conservation = 1d-3
```

### report_min_dr_div_cs

If true, produce terminal output about minimum of cell dr/cs

```
report_min_dr_div_cs = .false.
```

### report_dt_hard_limit_retries

If true, produce terminal output about choice of timestep.

```
report_dt_hard_limit_retries = .false.
```

### report_solver_dt_info

If true, produce terminal output about choice of timestep based on `varcontrol_target`

.

```
report_solver_dt_info = .false.
```

## debugging controls

### report_solver_progress

Set true to see info about solver iterations.

```
report_solver_progress = .false.
```

### report_ierr

If true, produce terminal output when have some internal error.

```
report_ierr = .false.
```

### report_bad_negative_xa

If true, produce terminal output when have bad negative mass fraction error.

```
report_bad_negative_xa = .false.
```

### stop_for_bad_nums

If true and report_ierr is also true, then stop for bad numbers (NaNs or infinity). this replaces old control stop_for_NaNs

```
stop_for_bad_nums = .false.
```

### show_mesh_changes

When `show_mesh_changes`

is true, the terminal output includes the `mesh_call_number`

.

```
show_mesh_changes = .false.
```

### trace_evolve

Send evolve output to screen.

```
trace_evolve = .false.
```

variety of output from the solver

```
solver_numerical_jacobian = .false.
solver_jacobian_nzlo = 1
solver_jacobian_nzhi = -1
solver_check_everything = .false.
solver_inspect_soln_flag = .false.
solver_test_partials_dx_0 = -1d0
solver_test_partials_k = -1
solver_test_partials_k_low = -1
solver_test_partials_k_high = -1
solver_test_eos_partials = .false.
solver_test_kap_partials = .false.
solver_test_net_partials = .false.
solver_test_atm_partials = .false.
solver_test_partials_var_name = ''
solver_test_partials_sink_name = ''
solver_test_partials_equ_name = ''
solver_test_partials_show_dx_var_name = ''
solver_show_correction_info = .false.
solver_test_partials_call_number = -1
solver_test_partials_iter_number = -1
solver_test_partials_write_eos_call_info = .false.
solver_epsder_struct = 1d-5
solver_epsder_chem = 1d-5
energy_conservation_dump_model_number = -1
```

### solver_save_photo_call_number

Saves a photo when solver_call_number = solver_save_photo_call_number - 1

```
solver_save_photo_call_number = -1
```

### xa_clip_limit

Abundances smaller than this limit are set to 0.

```
xa_clip_limit = 1d-99
```

### fill_arrays_with_NaNs

initialize arrays with NaNs to trap reads of uninitialized entries.

```
fill_arrays_with_NaNs = .false.
```

### zero_when_allocate

initialize arrays with zeros.

```
zero_when_allocate = .false.
```

## miscellaneous controls

### warn_rates_for_high_temp

If true then when any zone tries to evaluate a rate above `max_safe_logT_for_rates`

it generates a warning message. The code will cap the rate at the value
for `max_safe_logT_for_rates`

whether the warning is on or not.
10d0 is a sensible default for the max temperature, as that is where the partition tables
and polynomial fits to the rates are valid until.
warning messages include the text “rates have been truncated” and “WARNING: evaluating rates”.

```
warn_rates_for_high_temp = .true.
max_safe_logT_for_rates = 10d0
```

### warn_when_large_rel_run_E_err

message includes the text “WARNING: rel_run_E_err”

rel_run_E_err = abs(cumulative_energy_error/total_energy) you can turn off this warning message by setting this to a large number.

```
warn_when_large_rel_run_E_err = 0.1d0
```

### absolute_cumulative_energy_err

cumulative energy error is the sum of the absolute value of per-step errors. Set this to .false. to allow positive and negative errors to cancel when integrating over multiple steps.

```
absolute_cumulative_energy_err = .true.
```

### warn_when_stop_checking_residuals obsolete

### warning_limit_for_max_residual

message includes the text “WARNING: max_residual > warning_limit_for_max_residual”

```
warning_limit_for_max_residual = 1d0
```

### warn_when_large_virial_thm_rel_err

message includes the text “WARNING: virial_thm_rel_err” only applies to models with no velocities, rotation, or mass change.

```
warn_when_large_virial_thm_rel_err = 1d-2
```

### warn_when_get_a_bad_eos_result

message includes the text “WARNING eos:”

```
warn_when_get_a_bad_eos_result = .true.
```

### relax_dY

Change Y by this amount per step when relaxing Y.

```
relax_dY = 0.005d0
```

### relax_dlnZ

Change lnZ by this amount per step when relaxing Z. Default is ln10/10.

```
relax_dlnZ = 2.3025850929940459d-1
```

### eps_mdot_leak_frac_factor

```
eps_mdot_leak_frac_factor = 1d0
```

### zams_filename

Default is for Z=0.02, Y=0.28.

```
zams_filename = 'zams_z2m2_y28.data'
```

```
set_rho_to_dm_div_dV = .true.
```

### steps_before_start_stress_test

### stress_test_relax

```
steps_before_start_stress_test = 0
stress_test_relax = .false.
```

### use_other_{hook}

Logicals to deploy the use_other routines.

```
use_other_kap = .false.
use_other_diffusion = .false.
use_other_mlt_results = .false.
```

```
use_other_adjust_mdot = .false.
use_other_j_for_adjust_J_lost = .false.
use_other_alpha_mlt = .false.
use_other_am_mixing = .false.
use_other_brunt = .false.
use_other_brunt_smoothing = .false.
use_other_build_initial_model = .false.
use_other_cgrav = .false.
use_other_mesh_delta_coeff_factor = .false.
```

```
use_other_energy_implicit = .false.
use_other_energy = .false.
use_other_pressure = .false.
use_other_momentum_implicit = .false.
use_other_momentum = .false.
use_other_eps_grav = .false.
use_other_mesh_functions = .false.
use_other_D_mix = .false.
use_other_close_gaps = .false.
```

```
use_other_neu = .false.
use_other_net_get = .false.
use_other_solver_monitor = .false.
use_other_opacity_factor = .false.
use_other_diffusion_factor = .false.
use_other_diffusion_coefficients = .false.
use_other_pgstar_plots = .false.
use_other_gradr_factor = .false.
use_other_eval_fp_ft = .false.
use_other_torque = .false.
use_other_screening = .false.
use_other_rate_get = .false.
use_other_net_derivs = .false.
use_other_split_burn = .false.
```

```
use_other_torque_implicit = .false.
use_other_wind = .false.
use_other_after_struct_burn_mix = .false.
use_other_before_struct_burn_mix = .false.
use_other_surface_PT = .false.
use_other_remove_surface = .false.
use_other_set_pgstar_controls = .false.
use_other_accreting_state = .false.
use_other_eval_i_rot = .false.
```

```
use_other_export_pulse_data = .false.
use_other_get_pulse_data = .false.
use_other_edit_pulse_data = .false.
```

```
use_other_astero_freq_corr = .false.
```

```
use_other_timestep_limit = .false.
```

#### mixing diffusion coeffs

### sig_term_limit

Limit on coefficients in convective mixing equations. Consider a diffusion eqn of form:

```
x(k) - x0(k) = c1*(x(k-1) - x(k)) - c2*(x(k) - x(k+1))
```

Simplify for c1=c2=c, x(k-1)=x(k+1)=x0(k)=x0, x(k)=x0+dx Then eqn becomes

```
(1+2*c)*(x0+dx) - 2*c*x0 = x0
```

If `2*c >> 1`

, then eqn becomes ill-conditioned,
so we enforce `c <= sig_term_limit`

In physical terms c is `dt*sig/dm`

, where
`sig = (4 pi r^2 rho)^2*D`

and D = diffusion coeff (cm^2/s),
so c can get large when dt/dm is large.

```
sig_term_limit = 1d13
```

### am_sig_term_limit

Limit on coefficients in angular momentum transport equations.
Necessary for numerical stability.
Plays same role as `sig_term_limit`

for material mixing.

```
am_sig_term_limit = 1d13
```

### sig_min_factor_for_high_Tcenter

High center T limit to avoid negative mass fractions.
If Tcenter >= `Tcenter_min_for_sig_min_factor_full_on`

,
then okay to reduce sig by as much as this factor
as needed to prevent causing negative abundances.
Inactive when >= 1d0.

```
sig_min_factor_for_high_Tcenter = 0.01d0
```

### Tcenter_min_for_sig_min_factor_full_on

If Tcenter >= this, factor = `sig_min_factor_for_neg_abundances`

,
this should be > `Tcenter_max_for_sig_min_factor_full_off`

.

```
Tcenter_min_for_sig_min_factor_full_on = 3.2d9
```

### Tcenter_max_for_sig_min_factor_full_off

If Tcenter <= this, factor = 1, so has no effect
this should be < `Tcenter_min_for_sig_min_factor_full_on`

.
For T > `full_off`

and < `full_on`

, factor changes linearly with Tcenter.

```
Tcenter_max_for_sig_min_factor_full_off = 2.8d9
```

### max_delta_m_to_bdy_for_sig_min_factor

sig_min factor goes to 1 as distance (in Msun units) from boundary of mixing region reaches this value

```
max_delta_m_to_bdy_for_sig_min_factor = 0.5d0
```

### delta_m_upper_for_sig_min_factor

okay to change sig min factor to 1 for mix region larger than this

```
delta_m_upper_for_sig_min_factor = 0.3d0
```

### delta_m_lower_for_sig_min_factor

don’t change sig min factor for mix region smaller than this

```
delta_m_lower_for_sig_min_factor = 0.1d0
```

extra params as a convenience for developing new features
note: the parameter `num_x_ctrls`

is defined in `star_def.inc`

```
x_ctrl(1:num_x_ctrls) = 0d0
x_integer_ctrl(1:num_x_ctrls) = 0
x_logical_ctrl(1:num_x_ctrls) = .false.
x_character_ctrl(1:num_x_ctrls) = ''
```

One can split controls inlist into pieces using the following parameters. BTW: it works recursively, so the extras can read extras too.

### read_extra_controls_inlist(1..5)

### extra_controls_inlist_name(1..5)

If `read_extra_controls_inlist(1)`

is true, then read &controls from this namelist file.

```
read_extra_controls_inlist(:) = .false.
extra_controls_inlist_name(:) = 'undefined'
```

### save_controls_namelist

dumps all values for &controls namelist to file

```
save_controls_namelist = .false.
```

### controls_namelist_name

if empty, uses a default name

```
controls_namelist_name = ''
```