G62-46 - AN UNRESOLVED DOUBLE DEGENERATE BINARY CONTAINING A MAGNETIC DA COMPONENT

A detailed analysis of the white dwarf star G62-46 is presented. High signal-to-noise spectroscopy reveals Zeeman splitting of the Halpha line profile, indicating the presence of a magnetic field. Model atmosphere calculations are used to demonstrate that the observed energy distribution and line profiles cannot be reconciled with those of a single magnetic hydrogen-line (DA) white dwarf. Instead, G62-46 is shown to be an unresolved double degenerate binary, composed of a featureless DC white dwarf diluting the line profiles of the magnetic DA component. We show from the inferred mass of the DA component that the system most likely has undergone at least one phase of common envelope evolution. The observed line profiles of the DA star are reproduced with a dipole strength of B(d) = 7.4 MG, offset from the center of the star by an amount equal to about one-tenth of the stellar radius.