Flux and spectral variations in the Circinus Galaxy

被引:32
作者
Bianchi, S
Matt, G
Fiore, F
Fabian, AC
Iwasawa, K
Nicastro, F
机构
[1] Univ Roma Tre, Dipartimento Fis, I-00146 Rome, Italy
[2] Osserv Astron Roma, I-00044 Monte Porzio Catone, Italy
[3] Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England
[4] Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA
关键词
galaxies : individual : Circinus; galaxies : Seyfert X-rays : galaxies; X-rays : individuals : CG X-1 x-rays : individuals : CG X-2;
D O I
10.1051/0004-6361:20021414
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We report on a dramatic flux (similar to 50% increase in the LECS and MECS band) and spectral variation between two BeppoSAX observations of the Circinus Galaxy performed almost three years apart. Through the analysis of all Chandra observations available in the archive, including a new DDT observation on May 2001, we show that a high flux state of an extremely variable Ultra Luminous X-ray source (CG X-1: Bauer et al. 2001), which is within the adopted BeppoSAX source extraction region of 20, is the most likely explanation for most of the observed variation. However, the presence of a high flux 6.7 keV line and the spectral variation of the PDS in the new BeppoSAX data could be partly due to intrinsic variation of the nucleus. Comparing the longest Chandra observation and the BeppoSAX one, we find that the long-term flux variability of CG X-1 is not accompanied by a significant spectral variability. We also re-analysed the Chandra HEG nuclear spectra and report on the presence of a Compton shoulder with a flux of about 20% the line core, in agreement with theoretical expectations for Compton-thick matter.
引用
收藏
页码:793 / 799
页数:7
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