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DM-in-Stars

Explores the effects of dark matter (DM) on stellar evolution. Includes: (1) a module written to incorporate the effects of DM energy transport into the stellar evolution code MESA (Modules for Experiments in Stellar Astrophysics), and (2) supporting code to facilitate running MESA + DM models. This code was written for MESA version 12115. It is not compatible with more recent MESA versions, mostly due to a change to the star_info type.

Code used for the paper The Effects of Asymmetric Dark Matter on Stellar Evolution I: Spin-Dependent Scattering (Raen et al., 2021) is in the Raen2020 branch. The paper used MESA version 12115 and MESA SDK version 20190830.

Quick Start

  1. Install MESA by following the instructions here.
  2. Clone this repo git clone https://github.com/troyraen/DM-in-Stars.git
  3. Change settings in the inlist as desired (optional)
  4. Alter DM properties in inlist_DM as desired (optional, see below for details)
  5. Run a MESA + DM model using the following:
cd DM-in-Stars
./clean
./mk
./rn

Alternately, if one has existing code running MESA models, this DM module can be incorporated by copying inlist_DM and the contents of the src directory from this repo.

DM Parameters

The following are accessed through inlist_DM:

  1. DM mass (mxGeV [GeV])
  2. DM-proton cross section (sigmaxp [cm^2])
  3. Boost in DM capture rate relative to the solar environment (cboost, dimensionless). It encapsulates the environment's DM density and velocity dispersion. This variable is $\Gamma_B$ in the Raen 2020 paper.
  4. Spin dependent or independent scattering (spindep, Boolean). Currently, only the spin dependent option is fully functional.

Functionality

The following is computed (src/DM/DM_module.f90) for each time step in a MESA run:

  • Total number of DM particles captured.
  • Number density of DM as a function of distance from the center.
  • DM temperature.
  • Amount of energy transported as a result of DM-nucleon scattering events, as a function of distance from the center of the star. This quantity is then passed to MESA via the other_energy_implicit hook (src/run_star_extras.f).