On the nature of the magnetic DB white dwarfs

Abstract

We use recent calculations of the Zeeman splitting of neutral helium lines and atmospheric models to investigate the properties of the magnetic DB white dwarfs in the field range 10-1000 MG. We confirm that GD 229 exhibits spectroscopic signatures indicative of neutral helium in a magnetic field of ∼500 MG, and argue that HE 1043-0502 may also be helium rich with an even higher field of ∼750 MG. The dominant features in the phase-averaged spectrum of the polarized magnetic white dwarf HE 1211-1707 correspond with those of Zeeman split neutral helium lines in a mean field of ∼50 MG, while the observed spectral variations point to a non-dipolar field structure.