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

TL;DR

This paper reveals that KPD0005+5106 is the hottest known helium-rich white dwarf, with a temperature of 200,000 K, explaining its X-ray emission and suggesting a different evolutionary origin than previously thought.

Contribution

The study provides a revised temperature estimate for KPD0005+5106 and proposes a new evolutionary link to O(He) and RCrB stars based on spectral analysis.

Findings

KPD0005+5106 has a temperature of 200,000 K.

The star's X-ray emission is likely photospheric.

It is not a PG1159 descendant, but related to O(He) and RCrB stars.

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.