KPD0005+5106: Hottest DO White Dwarf Much Hotter Than Assumed

Abstract

KPD0005+5106 is the hottest known helium-rich white dwarf. We have identified NeVIII lines in UV and optical spectra and conclude that it is significantly hotter than previously thought, namely Teff=200,000 K instead of 120,000 K. This is a possible explanation for the observed hard X-ray emission as being of photospheric origin. Concerning its evolutionary state, we suggest that KPD0005+5106 is not a descendant of a PG1159 star but more probably related to the O(He) stars and RCrB stars.

To appear in proceedings of "Hydrogen-Deficient Stars" conference, held in Tuebingen, Germany, Sept. 17-21, 2007. 2 pages