MR relation

Module for interpolating white dwarf evolutionary models. For example calculating the white dwarf radius from a known Teff and logg, or the white dwarf cooling age from mass and radius.

By default the evolutionary models of Bedard et al. (2020) are used. Other model grids are included (see references) with more to be added over time. Let me know if you feel your evolutionary model grid should be included!

Generic routines are also included for calculting gravitational redshifts, and conversions between M/R/logg or L/R/Teff.

This module is compatible with astropy units. If arguments are provided without units, sensible defaults are assumed, e.g. Msun for mass, and the result is also returned without units. If either of the two interpolating arguments are input with units, the output is also returned with a unit attached.

A sub-module correct_3D is included for applying 3D corrections to parameters from 1D models, or the inverse.

Examples:

#No units provided
>>> R_from_Teff_M(15000, 0.6, 'thick')
0.013157301496275331

#Units on one argument
>>> R_from_Teff_M(15000*u.K, 0.6, 'thick')
<Quantity 0.0131573 solRad>

#Units on both arguments
>>> R_from_Teff_M(15000*u.K, 0.6*u.Msun, 'thick')
<Quantity 0.0131573 solRad>

#Non default unit used on an argument
>>> R_from_Teff_M(15000*u.K, 1.2E30*u.kg, 'thick')
<Quantity 0.01310131 solRad>

#Inputs can mix and match linear and log scales if units are provided
>>> M_from_logg_R(1E8*u.cm/u.s**2, -1.9*u.dex(u.Rsun))
<Quantity 0.57800603 solMass>
>>> M_from_logg_R(9.81*u.m/u.s**2, 0*u.dex(u.Rearth)).to(u.Mearth)
<Quantity 1.00118406 earthMass>

#Switching to a different grid (see references below for options)
>>> import MR_relation as MR
>>> MR.tau_from_Teff_M(10000*u.K, 0.6*u.Msun, 'thick')
<Quantity 0.6328035 Gyr>
>>> MR.MR_grid.set_grid('Fontaine01')
>>> MR.tau_from_Teff_M(10000*u.K, 0.6*u.Msun, 'thick')
<Quantity 0.60274991 Gyr>

Dependencies:

• numpy
• scipy
• astropy
• pandas

References:

• Bedard20: A. Bedard et al, ApJ 901, 26 (2020)
• Fontaine01: G. Fontaine et al, PASP 113, 409 (2001)
• Camisassa25: M. Camisassa, Astronomische Nachrichten 346, e20240118 (2025)
• Althaus13ELM: L. Althaus et al, A&A 557 19 (2013)

NB: Only the monotonic cooling part of the Althaus ELM models are used so that all interpolation functions will work correctly.