The white dwarf mass-radius relation and its dependence on the hydrogen envelope

Abstract

We present a study of the dependence of the mass-radius relation for DA white dwarf stars on the hydrogen envelope mass and the impact on the value of log g, and thus the determination of the stellar mass. We employ a set of full evolutionary carbon-oxygen core white dwarf sequences with white dwarf mass between 0.493 and 1.05 Msun. Computations of the pre-white dwarf evolution uncovers an intrinsic dependence of the maximum mass of the hydrogen envelope with stellar mass, i.e., it decreases when the total mass increases. We find that a reduction of the hydrogen envelope mass can lead to a reduction in the radius of the model of up to ~12%. This translates directly into an increase in log g for a fixed stellar mass, that can reach up to 0.11 dex, mainly overestimating the determinations of stellar mass from atmospheric parameters. Finally, we find a good agreement between the results from the theoretical mass-radius relation and observations from white dwarfs in binary systems. In particular, we find a thin hydrogen mass of MH ~ 2 10^-8 Msun, for 40 Eridani B, in agreement with previous determinations. For Sirius B, the spectroscopic mass is 4.3% lower than the dynamical mass. However, the values of mass and radius from gravitational redshift observations are compatible with the theoretical mass-radius relation for a thick hydrogen envelope of MH = 2 10^-6 Msun.

Accepted for publication in MNRAS

References in corpus (7)

• Updated Electron-Conduction Opacities: The Impact on Low-Mass Stellar Models
• The initial-final mass relationship of white dwarfs revisited: effect on the luminosity function and mass distribution
• Relativistic deflection of background starlight measures the mass of a nearby white dwarf star
• Testing the white dwarf mass-radius relationship with eclipsing binaries
• The Physics of Crystallization from Globular Cluster White Dwarf Stars in NGC 6397
• The Gaia DR1 Mass-Radius Relation for White Dwarfs
• The age-metallicity dependence for white dwarfs

Cited by in corpus (7)

• A new class of Roche lobe-filling hot subdwarf binaries
• From Hydrogen to Helium: The Spectral Evolution of White Dwarfs as Evidence for Convective Mixing
• A Gravitational Redshift Measurement of the White Dwarf Mass-Radius Relation
• On the existence of warm H-rich pulsating white dwarfs
• Evidence of Spectral Evolution on the white dwarf sample from the Gaia Mission
• A far-UV survey of three hot, metal-polluted white dwarf stars: WD0455-282, WD0621-376, and WD2211-495
• Pulsation in the white dwarf HE 1017-1352: confirmation of the class of hot DAV stars