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A color gradient in the soft X-ray diffuse backgroundIt is shown that the deviations of the soft X-ray diffuse background B band to C band intensity ratio from a constant value can be described as a simple dipole-like variation across the sky. In terms of the observed Wisconsin B/C band intensity ratio, the mean value is 0.355, the dipole magnitude is 0.106, and the positive dipole axis points toward l = 168.7 deg, b = 11.2 deg, almost in the galactic anticenter direction. This gradient in the spectral hardness can be due to several causes; the simplest is a temperature gradient in the X-ray emitting plasma of the local cavity from about 10 exp 6.2 K toward the galactic center to about 10 exp 5.9 K in the anticenter direction. While the physical origin of such a temperature gradient is uncertain, the alignment of the dipole with the higher temperature (and absorbed) Loop I region may be significant.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Snowden, S. L.
(Wisconsin, University Madison; Max-Planck-Institut fuer Extraterrestrische Physik, Garching, Federal Republic of Germany, United States)
Schmitt, J. H. M. M.
(Max-Planck-Institut fuer Extraterrestrische Physik Garching, Federal Republic of Germany, United States)
Edwards, B. C.
(Wisconsin, University Madison, United States)
Date Acquired
August 15, 2013
Publication Date
November 20, 1990
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 364
ISSN: 0004-637X
Subject Category
Funding Number(s)
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