Published in

American Astronomical Society, Astronomical Journal, 1(127), p. 477-480, 2004

DOI: 10.1086/380230

Links

Tools

Export citation

Search in Google Scholar

Hard X-Ray Emission Associated with White Dwarfs. II.

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

Full text: Download

Red circle
Preprint: archiving forbidden
Red circle
Postprint: archiving forbidden
Green circle
Published version: archiving allowed
Data provided by SHERPA/RoMEO

Abstract

We have previously conducted a search for X-ray sources coincident with white dwarfs using the white dwarf catalog compiled by McCook & Sion and the ROSAT sources in the WGA Catalog (Paper I). To include the white dwarfs discovered since 1999 and to include the X-ray sources detected in ROSAT Position Sensitive Proportional Counter (PSPC) observations made with a boron filter, we have carried out another search using an updated list of white dwarfs and the final catalogs of the ROSAT PSPC observations with and without a boron filter. Forty-seven new X-ray sources convincingly coincident with white dwarfs are found and reported in this paper. Among these, only five show hard X-ray emission: three possess confirmed or suggested late-type companions, one is apparently single, and the other is likely a misclassified BL Lac object. The apparently single white dwarf with hard X-ray emission, KPD 0005+5106, was discussed extensively in Paper I. Photospheric origin for the hard X-ray emission from hot DO and DQZO white dwarfs remains a tantalizing possibility, but high-quality near-IR spectroscopic observations and monitoring of the Hα emission line are needed to rule out the existence of a faint dMe companion.