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Chandra Observations of Magnetic White Dwarfs and their Theoretical ImplicationsObservations of cool DA and DB white dwarfs have not yet been successful in detecting coronal X-ray emission, but observations of late-type dwarfs and giants show that coronae are common for these stars. To produce coronal X-rays, a star must have dynamo-generated surface magnetic fields and a well-developed convection zone. There is some observational evidence that the DA star LHS 1038 and the DB star GD 358 have weak and variable surface magnetic fields. It has been suggested that such fields can be generated by dynamo action, and since both stars have well-developed convection zones, theory predicts detectable levels of coronal X-rays from these white dwarfs. However, we present analysis of Chandra observations of both stars showing no detectable X-ray emission. The derived upper limits for the X-ray fluxes provide strong constraints on theories of formation of coronae around magnetic white dwarfs. Another important implication of our negative Chandra observations is the possibility that the magnetic fields of LHS 1038 and GD 358 are fossil fields.
Document ID
20040000492
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Musielak, Z. E.
(Texas Univ. Arlington, TX, United States)
Noble, M.
(Texas Univ. Arlington, TX, United States)
Porter, J. G.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Winget, D. E.
(Texas Univ. Austin, TX, United States)
Date Acquired
August 21, 2013
Publication Date
August 10, 2003
Publication Information
Publication: The Astrophysical Journal
Publisher: American Astronomical Society
Volume: 593
Subject Category
Astrophysics
Funding Number(s)
CONTRACT_GRANT: GO1-2003A
Distribution Limits
Public
Copyright
Other

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