Hard X-ray Emission Associated with White Dwarfs II

Abstract

We have previously conducted a search for X-ray sources coincident with white dwarfs using the white dwarf catalog compiled by McCook & Sion (1999} and the ROSAT sources in the WGACAT (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 5 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 H-alpha emission line are needed to rule out the existence of a faint dMe companion.

10 pages, 1 table, no figures, accepted for publication in the Astronomical Journal, 2004 January issue

References in corpus (5)

• The FIRST Bright Quasar Survey. II. 60 Nights and 1200 Spectra Later
• The Enigmatic X-ray Point Sources at the Central Stars of NGC 6543 and NGC 7293
• Hard X-ray Emission Associated with White Dwarfs
• Resolving Sirius-like binaries with the Hubble Space Telescope
• Variable H-alpha Line Emission from the Central Star of the Helix Nebula

Cited by in corpus (13)

• Post common envelope binaries from SDSS. XII: The orbital period distribution
• Progenitors of Type Ia Supernovae: Binary Stars with White Dwarf Companions
• The Chandra Planetary Nebulae Survey (ChanPlaNS): III. X-ray Emission from the Central Stars of Planetary Nebulae
• The creation of the Helix planetary nebula (NGC 7293) by multiple events
• X-Ray-Emitting Stars Identified from the ROSAT All-Sky Survey and the Sloan Digital Sky Survey
• X-ray Emission from the Binary Central Stars of the Planetary Nebulae HFG 1, DS 1, and LoTr 5
• Numerical Simulations of Gaseous Disks Generated from Collisional Cascades at the Roche Limits of White Dwarf Stars
• Searching for X-ray emission from AGB stars
• X-ray photolysis of CH${}_3$COCH${}_3$ ice: Implications for the radiation effects of compact objects towards astrophysical ices
• Perfecting our set of spectrophotometric standard DA white dwarfs
• Hard X-ray Emission Associated with White Dwarfs. IV. Signs of Accretion from Sub-stellar Companions
• Spectral Classification of Optical Counterparts to ROSAT All-Sky Survey X-ray Sources
• Synthetic X-ray emission from white dwarf accreting planetary material