wdwarfdate

\(\texttt{wdwarfdate}\) is a Python open source code which derives a Bayesian age of a white dwarf from an effective temperature and a surface gravity. \(\texttt{wdwarfdate}\) runs a chain of models assuming single star evolution and estimate the following parameters and their uncertainties: total age of the object, mass and cooling age of the white dwarf and mass and lifetime of the progenitor star.

Basic usage

Let’s set up two white dwarfs with their effective temperature and surface gravity. These two white dwarfs parameters come from Cummings,J.D. et al. (2018). To run \(\texttt{wdwarfdate}\) we just need to initialize the object WhiteDwarf() with the parameters indicating the models we want to use. For details on these parameters go to the tutorials in this documentation.

import wdwarfdate
import numpy as np

#Define data for the white dwarfs
teffs = np.array([19250,20250])
teffs_err = np.array([500,850])
loggs = np.array([8.16,8.526])
loggs_err = np.array([0.084,0.126])

WD = wdwarfdate.WhiteDwarf(teffs,teffs_err,loggs,loggs_err,
                           model_wd='DA',
                           feh='p0.00',
                           vvcrit='0.0',
                           model_ifmr = 'Cummings_2018_MIST',
                           high_perc = 84,
                           low_perc = 16,
                           datatype='yr',
                           save_plots=False,
                           display_plots=True)
WD.calc_wd_age()

The function WD.calc_wd_age() will take the effective temperature (\(T_{\rm eff}\)) and surface gravity (\(\log g\)) given, and will sample the posterior distribution defined by the chosen models using the grid method. The parameters which are being sampled are the mass of the progenitor star, the cooling age of the white dwarf and a \(\Delta _{\rm m}\) parameter to model the scatter in the initial-to-final mass relation. For more information on how to run \(\texttt{wdwarfdate}\) see the tutorials and Kiman et al. in prep.

\(\texttt{wdwarfdate}\) allows us to select which models are going to go into the chain of models for the age estimation: 1. Cooling tracks for a DA or non-DA white dwarf. 2. The initial-to-final mass relation. 3. The parameter for the progenitor star . For details on the models available see the page Models included and Kiman et al. in prep.

The output is saved on a table, and can be accessed by doing

WD.results

This is an astropy Table with one row for each \(T_{\rm eff}\) and \(\log g\) given. The columns of the Table correspond to median, the difference between median and low percentile (16th unless indicated otherwise), and the difference between high percentile and median (84th unless indicated otherwise) for the following parameters:

ms_age Median values of main sequence age distribution of the progenitor of the white dwarf
cooling_age Median values of cooling age distribution of the white dwarf
total_age Median values of total age distribution of the white dwarf
initial_mass Median values of initial mass distribution, meaning the mass of the progenitor
final_mass Median values of final mass distribution, meaning the mass of the white dwarf

User Guide

Tutorials

License

MIT License

More information here