The Halo White Dwarf WD 0346+246 Revisited

Abstract

The extremely helium-rich atmospheric composition determined for the halo white dwarf WD 0346+246 is reexamined. This solution is shown to be improbable from an astrophysical point of view when accretion of hydrogen and metals from the interstellar medium is taken into account. An alternate solution is proposed in which hydrogen and helium are present in the atmospheric regions in equal amounts. The best fit, at T_eff = 3780 K, log g = 8.34, and N(He)/N(H) = 1.3, is achieved by including in the model calculations a bound-free opacity from the Lyman edge associated with the so-called dissolved atomic levels of the hydrogen atom, or pseudocontinuum opacity.