CoolDwarf Project

Welcome to the CoolDwarf project. This project aims to provide a easy to use and physically robsut 3D cooling model for fully convective stars.

CoolDwarf is in very early stages of development and is not yet ready for general or scientific use. However, we welcome any feedback or contributions to the project.

The CoolDwarf project is hosted on GitHub at https://github.com/tboudreaux/CoolDwarf

Depedenices

CoolDwarf requires the following packages to be installed:

  • numpy

  • scipy

  • matplotlib

  • tqdm

  • torch

Optional packages:

  • cupy

If you are using a CUDA enabled GPU, you can install the cupy package to speed up the calculations significantly. If you do not have a CUDA enabled GPU, you can still use the package, but it will be significantly slower. CoolDwarf will automatically detect if cupy is installed and use it if it is available.

Installation

To install the CoolDwarf package, you can use the following command:

git clone https://github.com/tboudreaux/CoolDwarf.git
cd CoolDwarf
pip install .

Usage

The CoolDwarf package is designed to be easy to use. The primary entry point for using the package is the CoolDwarf.star.VoxelSphere class. This class is used to create a 5D model of a star.

The model is contructed of a grid of equal volume elements spread over a sphere. A MESA model is used to provide the initial temperature and density profiles of the star. An equation of state from Chabrier and Debras 2021 is used to calculate the pressure and energy of the star. The radiative opacity of the star is currentl treated monocromatically and with a simplistic Kramer’s opacity model (this is a high priority area for improvement).

Evolution of the Cooling model is preformed by calculating the radiative and convective energy gradients at each grid point and to find the new energy after some small time step. The Equation of state is then inverted to update the density, temperature, and pressure of the model.

Timesteps are dynamicall calculated using the Courant-Friedrichs-Lewy (CFL) condition. The CFL condition is used to ensure that the timestep is small enough to prevent the model from becoming unstable. If the user wishes to use a fixed timestep, they can set the cfl_factor to infinity. Alternativley the timestep can be fixed by setting it lower than the CFL condition.

Currently, numerical instabilities exist; however, we are working to resolve these issues. A breif example of how to use the package is shown below (note that neither the EOS tables nor the MESA model are included in the repository; however, these are either readily available online (in the case of the EOS model) or can be generated easily using MESA):

from CoolDwarf.star import VoxelSphere, default_tol
from CoolDwarf.utils import setup_logging
from CoolDwarf.EOS import get_eos
from CoolDwarf.opac import KramerOpac
from CoolDwarf.utils.output import binmod

modelWriter = binmod()

setup_logging(debug=False)

EOS = get_eos("EOS/TABLEEOS_2021_Trho_Y0292_v1", "CD21")
opac = KramerOpac(0.7, 0.02)
sphere = VoxelSphere(
   8e31,
   "BrownDwarfMESA/BD_TEST.mod",
   EOS,
   opac,
   radialResolution=100,
   altitudinalResolition=100,
   azimuthalResolition=100,
   cfl_factor = 0.4,
)
sphere.evolve(maxTime = 60*60*24, pbar=False)

Contents:

Indices and tables