Finding the unusual red giant remnants of cataclysmic variable mergers

Basic information

This repository contains inlists and files required to reproduce the models included in Rui & Fuller 2024 (“Finding the unusual red giant remnants of cataclysmic variable mergers”). These models are run using version r10398 of the Modules for Experiments in Stellar Astrophysics (MESA) code.

Included files are as follows:

• mesa/: Contains template MESA directories.
• jobshell_templates/: Contains template job shell files for submitting jobs to the Slurm Workload Manager, the scheduler on the Caltech Wheeler computer cluster on which these models were run.
• m_plus_wd_makedirs.py: A file of python scripts which, given appropriate inputs, automatically creates MESA directories with the required modifications, as well as job shells which can be used to run them on a computer cluster using Slurm.

Workflow

Conceptually, our modeling workflow is partitioned into 5+1 “stages,” which are reflected in the naming of files. These are, in order:

• stage1: Original single stellar model.
• stage2: Strip mass off of the single stellar model in stage1. This is done either to create a helium white dwarf or a partially stripped red giant.
• stage3: Evolve the stripped model created in stage2. This either evolves a helium white dwarf along a cooling track or follows the evolution of a single star.
• stage4: Removes mass from the original model in stage1 to create a scaffold model for the merger remnant, and then combines it with a cooled helium white dwarf model in stage3 to create a merger remnant model.
• stage5: Evolves the merger remnant model created in stage4.
• testLi: Resumes merger remnant evolution right before the tip of the red giant branch, after manually removing all lithium to test whether it is enriched during the helium flash.

Template MESA directories combine stages 2+3 (stage23), as well as stages 4+5 (stage45). stage1 is a prerequisite for stage23, which is a prerequisite for stage45, which is a prerequisite for testLi.

Step-by-step instructions

• Download and install MESA version r10398.
• Download the contents of this repository.
• Change the variable names at the beginning of m_plus_wd_makedirs.py to reflect the locations of downloaded files on your own machine. Variables with suffix *_template refer to MESA directory/job shell templates included in this download. model_dir and job_dir refer to the paths where this code will create MESA directories and job shell files, respectively.
• Run the functions make_stage1, make_stage23, make_stage45, and make_testLi defined in m_plus_wd_makedirs.py to create desired MESA directories/job shell files. Arguments to these functions are defined in the docstrings. Note the common dependencies ipython, numpy, astropy, shutil, and os, which are all included in Anaconda. As described in "Workflow" above, certain MESA directories can only be created once certain prerequisite MESA runs have been completed.
• Compile and run resulting MESA directories either in the usual way or by submitting the included job shells (if working on a computing cluster using Slurm).