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THE UNUSUAL X-RAY BINARIES OF THE GLOBULAR CLUSTER NGC 6652.
- Source :
- Astrophysical Journal; Jul2011, Vol. 735 Issue 2, p1-8, 8p
- Publication Year :
- 2011
-
Abstract
- Our 5 ks Chandra ACIS-S observation of the globular cluster NGC 6652 detected seven X-ray sources, three of which were previously unidentified. This cluster hosts a well-known bright low-mass X-ray binary, source A (or XB 1832-330). Source B shows unusual rapid flaring variability, with an average L<subscript>X</subscript> (0.5-10 keV) ~2 × 10<superscript>34</superscript> erg s<superscript>-1</superscript>, but with minutes-long flares up to L<subscript>X</subscript> = 9 × 10<superscript>34</superscript> erg s<superscript>-1</superscript>. Its spectrum can be fit by an absorbed power law of photon index Γ ~ 1.24 and hardens as the count rate decreases. This suggests that part or all of the variation might be due to obscuration by the rim of a highly inclined accretion disk. Sources C and D, with L<subscript>X</subscript> ~ 10<superscript>33</superscript> erg s<superscript>-1</superscript>, have soft and unusual spectra. Source C requires a very soft component, with a spectrum peaking at 0.5 keV, which might be the hot polar cap of a magnetically accreting polar cataclysmic variable. Source D shows a soft spectrum (fit by a power law of photon index ~2.3) with marginal evidence for an emission line around 1 keV; its nature is unclear. The faint new sources E, F, and G have luminosities of 1-2 × 10<superscript>32</superscript> erg s<superscript>-1</superscript>, if associated with the cluster (which is likely). E and F have relatively hard spectra (consistent with power laws with photon index ~1.5). G lacks soft photons, suggesting absorption with N<subscript>H</subscript> > 10<superscript>22</superscript> cm<superscript>-2</superscript>. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 0004637X
- Volume :
- 735
- Issue :
- 2
- Database :
- Complementary Index
- Journal :
- Astrophysical Journal
- Publication Type :
- Academic Journal
- Accession number :
- 83589582
- Full Text :
- https://doi.org/10.1088/0004-637X/735/2/95