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 Ha mburg/ESO survey for bright quasi-stellar objects. Two objects, HE 1211-170 7 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 similar to 5 0 and similar to 800 MG, respectively. The former is also found to be rotat ing with a period of similar to2 h. HE 1045-0908 is a hydrogen-line star wi th a polar field strength of similar to 20 MG, spinning with a period in th e range similar to2-4 h. Attempts at modelling the limited amount of phase- resolved data that is available suggest that the field structure on this st ar departs substantially from a simple centred dipolar geometry. Two cool w hite dwarfs with unidentified broad absorption spectral features, HE 0236-2 656 and HE 0330-0002, are polarimetrically confirmed to be magnetic. Line i dentifications for these stars are not yet possible, but the atmospheres ar e 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. alongside two similar objects to be magneti c 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 exte nsion all four, are non-magnetic white dwarf + cool dwarf pairs. They deser ve to be studied in their own right as possible close binaries. Finally, a lack of circular polarization suggests that HE 0000-3430 and HE 0127-3110 a re also non-magnetic. HE 0000-3430 appears to be a featureless DC white dwa rf over the spectral range observed here, while the sole absorption line ne ar 5890 Angstrom in HE 0127-3110 could be either He I lambda 5876 or the Na I D doublet, but there are difficulties with either interpretation.