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 M _ { \odot } .
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 \sim 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 M _ { H } \sim 2 \times 10 ^ { -8 } M _ { \odot } , 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 M _ { H } = 2 \times 10 ^ { -6 } M _ { \odot } .