Radius-expansion burst spectra from 4U 1728-34: an ultracompact binary?

Recent theoretical and observational studies have shown that ashes from thermonuclear burning may be ejected during radius-expansion bursts, giving rise to photoionisation edges in the X-ray spectra. We report a search for such features in Chandra spectra observed from the low-mass X-ray binary 4U 1...

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Bibliographic Details
Published in:arXiv.org 2010-09
Main Authors: Galloway, Duncan K, Yao, Yangsen, Marshall, Herman, Misanovic, Zdenka, Weinberg, Nevin
Format: Article
Language:English
Subjects:
Ashes
Bursts
Gamma rays
Hydrogen
Nuclear fuels
Photoionization
X ray binaries
X ray spectra
X ray stars
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Summary:Recent theoretical and observational studies have shown that ashes from thermonuclear burning may be ejected during radius-expansion bursts, giving rise to photoionisation edges in the X-ray spectra. We report a search for such features in Chandra spectra observed from the low-mass X-ray binary 4U 1728-34. We analysed the spectra from four radius-expansion bursts detected in 2006 July, and two in 2002 March, but found no evidence for discrete features. We estimate upper limits for the equivalent widths of edges of a few hundred eV, which for the moderate temperatures observed during the bursts, are comparable with the predictions. During the 2006 July observation 4U 1728-34 exhibited weak, unusually frequent bursts (separated by
ISSN:2331-8422
DOI:10.48550/arxiv.1009.2296