HEATING IN AN EXTENDED ACCRETION DISK CORONA ALONG THE Z-PATTERN IN CYG X-2
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Author(s)
Schulz, Norbert S.
Huenemoerder, David P.
Ji, Li
Yao, Y.
Canizares, Claude R.
Date Issued
January 2009
Journal
Astrophysical Journal
Publisher
American Astronomical Society
Citation
"Heating in an Extended Accretion Disk Corona Along the Z-Pattern in Cyg X-2."
N. S. Schulz, D. P. Huenemoerder, L. Ji, M. Nowak, Y. Yao, and C. R. Canizares 2009 ApJ 692 L80-L83 doi: 10.1088/0004-637X/692/2/L80 (C)2009 The American Astronomical Society
Version
Final published version
Abstract
We observed at very high spectral resolution the prototype Z-source Cyg X-2 twice along its entire X-ray spectral variation pattern. In this preliminary analysis, we find an extended accretion disk corona (ADC) exhibiting Lyα emissions from various H-like ions, as well as emissions from He-like ions of Fe and Al, and Be-like ions of Fe. The brightest lines show a range of line broadening: H-like lines are very broad with Doppler velocities between 1100 and 2700 km s[superscript –1], while some others are narrower with widths of a few hundred km s[superscript –1]. Line diagnostics allow us for the first time to determine coronal parameters. The line properties are consistent with a stationary, extended up to 1010 cm, dense (1 × 10[superscript 15] cm[superscript –3]), and hot (log ξ > 3; T > 10[superscript 6] K) ADC. We find ongoing heating of the corona along the Z-track and determine that heating luminosities change from about 0.4×L[subscript Edd] on the horizontal to about 1.4 × L[subscript Edd] on the flaring branch.
MIT Department
MIT Kavli Institute for Astrophysics and Space Research
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DOI of Published Version
http://dx.doi.org/10.1088/0004-637X/692/2/L80
