# make_co_wd¶

This test builds a carbon-oxygen white dwarf starting from a specified pre main-sequence mass. It does this by running through a series of inlists for different stages of evolution. By default, the first two steps (pre main-sequence and main-sequence through core helium burning) are skipped so that the test will run in a reasonable amount of time, and the test produces a 0.6 $${\rm M}_\odot$$ white dwarf from a roughly 3 $${\rm M}_\odot$$ progenitor.

Starting from the beginning to produce a white dwarf descended from a progenitor of different mass or metallicity can be accomplished by editing the values assigned to initial_mass or initial_z in inlist_common.

Larger values for initial_mass can be used to produce more massive carbon-oxygen white dwarfs, but note that this test produces only an approximate initial-to-final-mass relation (IFMR). The test is designed to truncate the AGB evolution at the beginning of the thermally-pulsing AGB (TP-AGB) stage, which can be difficult and/or resource-intensive to model.

The five steps in this procedure are:

## 1. inlist_zams (optional)¶

This step starts from the pre main-sequence to produce a ZAMS model with the initial mass and metallicity specified in inlist_common.

## 2. inlist_to_end_he_core_burn (optional)¶

This step evolves from ZAMS through the end of core helium burning.

## 3. inlist_co_core¶

This step evolves to near the end of shell helium burning, producing the final C/O core profile in the interior. This step terminates when a thermal pulse occurs in the helium shell.

## 4. inlist_remove_env¶

This step removes the AGB envelope using the star_relax_to_star_cut method in src/run_star_extras.f90. The location of the cut is specified using x_ctrl(1) to leave $$10^{-3}$$ $${\rm M}_\odot$$ of the hydrogen envelope. After the relaxation ends, residual burning will reduce the final hydrogen envelope mass to around $$10^{-4}$$ $${\rm M}_\odot$$ (for the default 0.6 $${\rm M}_\odot$$ white dwarf).

## 5. inlist_settle¶

This step turns on diffusion in the young proto-WD model to allow the model to settle into a stratified envelope structure with a pure hydrogen atmosphere. This final step ends when the white dwarf has cooled down to reach a luminosity of 1 $${\rm L}_\odot$$.