A new hot DA white dwarf in a region of exceptionally low HI density.
Kepler, S. O.; Fontaine, G.; Barstow, M. A.; Bergeron, P.; Wesemael, F.; Holberg, J. B.; Buckley, D. A. H.; Stobie, R. S.; Irwin, M. J.; Rosen, S. R.; Vennes, S.; Lamontagne, R.; Mittaz, J. P. D.; Demers, S.
Abstract
We report the discovery of the hot DA white dwarf RE 0457-281 which has the lowest line-of-sight neutral hydrogen column density yet measured. The star was found independently by the ROSAT EUV, Montreal-Cambridge-Tololo and Edinburgh-Cape surveys. With an effective temperature of 60700 K and very soft EUV spectrum, this white dwarf resembles the well-studied hot DA white dwarf G 191-B2B. A follow-up observation made using the Voyager 2 UV spectrometer reveals a strong continuum shortward of the 912-Å Lyman limit from which we deduce that the neutral hydrogen column density is 1.3 × 1017 atom cm-2.