Studies of magnetic and suspected-magnetic southern white dwarfs

Optical spectrophotometry and circular spectropolarimetry are presented for several candidate magnetic white dwarfs that were identified during the Hamburg/ESO survey for bright QSOs. Two objects, HE 1211−1707 and HE 1043−0502, are shown to be rare examples of white dwarfs that show neutral helium lines in a high magnetic field, in these cases ∼50 MG and ∼800 MG, respectively. The former is also found to be rotating with a period of ∼2 hr. HE 1045−0908 is a hydrogen-line star with a polar field strength of ∼20 MG, spinning with a period in the range ∼2− 4 hr. Attempts at modeling the limited amount of phase-resolved data that is available suggest that the field structure on this star departs substantially from a simple centered dipolar geometry. Two rather cool white dwarfs with unidentified broad absorption spectral features, HE 0236−2656 and HE 0330−0002, are confirmed polarimetrically to be magnetic. Line identifications for these stars are not yet possible, but the atmospheres are probably helium-rich, with spectral features formed by trace compounds of hydrogen, carbon, and perhaps other metals. HE 0003−5701 and HE 0338−3853 were proposed by Reimers et al. (1996) alongside two similar objects to be magnetic DB white dwarfs, with Zeeman-split lines of helium in magnetic fields all near 20 MG. However, our observations show that the first two, and by extension all four, are nonmagnetic white dwarf + cool dwarf pairs. They are deserving of study in their own right as possible close binaries. Finally, a lack of circular polarisation suggests that HE 0000−3430 and HE 0127−3110 are also nonmagnetic. HE 0000−3430 appears to be a featureless DC white dwarf over the spectral range observed here, while the sole absorption line near 5890 Å in HE 0127−3110 could be either He I λ5876 or the Na I D doublet, but there are difficulties with either interpretation.