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A Chandra Search for Coronal X Rays from the Cool White Dwarf GD 356We report observations with the Chandra X-ray Observatory of the single, cool, magnetic white dwarf GD 356. For consistent comparison with other X-ray observations of single white dwarfs, we also re-analyzed archival ROSAT data for GD 356 (GJ 1205), G 99-47 (GR 290 = V1201 Ori), GD 90, G 195-19 (EG250 = GJ 339.1), and WD 2316+123 and archival Chandra data for LHS 1038 (GJ 1004) and GD 358 (V777 Her). Our Chandra observation detected no X rays from GD 356, setting the most restrictive upper limit to the X-ray luminosity from any cool white dwarf - Lx less than 6.0 x 10(exp 25) erg s(sup -1), at 99.7% confidence, for a 1- keV thermal-bremsstrahlung spectrum. The corresponding limit to the electron density is no less than 4.4x10(exp 11) per cubic centimeter. Our re-analysis of the archival data confirmed the non-detections reported by the original investigators. We discuss the implications of our and prior observations on models for coronal emission from white dwarfs. For magnetic white dwarfs, we emphasize the more stringent constraints imposed by cyclotron radiation. In addition, we describe (in an appendix) a statistical methodology for detecting a source and for constraining the strength of a source, which applies even when the number of source or background events is small.
Document ID
20070002064
Acquisition Source
Marshall Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Weisskopf, Martin C.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Wu, Kinwah
(University Coll. London, United Kingdom)
Trimble, Virginia
(California Univ. Irvine, CA, United States)
ODell, Stephen L.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Elsner, Ronald F.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Zavlin, Vyacheslav E.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Kouveliotou, Chryssa
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Date Acquired
August 24, 2013
Publication Date
January 1, 2006
Subject Category
Astronomy
Distribution Limits
Public
Copyright
Other

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