Schmidt, Gary D.

The new magnetic white dwarf PG 1031 + 234 - Polarization and field structure at more than 500 milion Gauss

The discovery and study of a PG white dwarf which shows strong linear and circular polarization modulated with a rotation period of 3 hr 24 min is reported. The new star, PG 1031 + 234, is more highly magnetic than even Grw +70 deg 8247, with absorption components of hydrogen in its optical and UV spectra corresponding to fields from 200 to more than 500 MG. An asymmetric dependence of polarization on rotational phase shows that the surface field structure on the star is more complex than a simple centered dipole. The basic observational features can be well reproduced by a rotating star containing an oblique centered dipole punctuated near its magnetic equator by a high-field spot containing primarily radial field lines.