PI: Ian J O'Dwyer, University of Illinois at Urbana-Champaign, email@example.com
Address: 1002 West Green Street, Urbana, IL 61801, USA
CoI: Robert Gruendl, University of Illinois at Urbana-Champaign
CoI: You-Hua Chu, University of Illinois at Urbana-Champaign
CoI: Martin A Guerrero, University of Illinois at Urbana-Champaign
Title: An Infrared Search for Binary Companions to White Dwarfs with Hard X-Ray Emission
Abstract: A white dwarf (WD) can emit soft (\ll 0.4 keV) X-rays, if it is hot enough, i.e., T_eff > 30,000 K for a pure hydrogen atmosphere or T_eff > 100,000 K for a hydrogen and helium atmosphere. A WD can also emit harder (> 0.5 keV) X-rays, if it has a close binary companion and mass transfer takes place, e.g., dwarf novae, polars, and cataclysmic variables. \null We found a large number of hard X-ray emitting WDs by cross-correlating the McCook & Sion (1999) catalog of WDs with the ROSAT point source database. We have verified the position of the WD, analysed the ROSAT data and extracted X-ray spectra to confirm the hard X-ray component. Since the only current explanation for hard X-ray emission from a WD involves a stellar companion and only five of the ~40 WDs that exhibit hard X-ray emission are known binary systems, we wish to investigate whether hard X-ray emssion is a useful diagnostic for the presence of companions to WDs. \null We request KPNO 2.1m SQIID near infrared photometric observations of a sample of 34 WDs, 23 of which exhibit hard X-ray emission, to look for an infrared excess consistent with the presence of a stellar companion.
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