A search for changing-look AGN in the Grossan catalog

被引:72
作者
Bianchi, S
Guainazzi, M
Matt, G
Chiaberge, M
Iwasawa, K
Fiore, F
Maiolino, R
机构
[1] European Space Astron Ctr, ESA, Newton Sci Operat Ctr, XMM, Madrid 28080, Spain
[2] Univ Roma Tre, Dipartimento Fis, I-00146 Rome, Italy
[3] Space Telescope Sci Inst, Baltimore, MD 21218 USA
[4] CNR, Ist Radioastron, INAF, I-40129 Bologna, Italy
[5] Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England
[6] Osserv Astron Roma, INAF, I-00040 Monte Porzio Catone, Italy
[7] Osserv Astrofis Arcetri, INAF, I-50125 Florence, Italy
关键词
galaxies : Seyfert; X-rays : galaxies; X-rays : individual : NGC 7674; X-rays : individual : IRAS 13218+0552;
D O I
10.1051/0004-6361:20053389
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We observed with XMM-Newton 4 objects selected from the Grossan ( 1992, Ph. D. Thesis) catalog, with the aim to search for new "changing-look" AGN. The sample includes all the sources which showed in subsequent observations a flux much lower than the one measured with HEAO A-1: NGC 7674, NGC 4968, IRAS 13218+0552 and NGC 1667. None of the sources was caught in a high flux state during the XMM-Newton observations, whose analysis reveal they are all likely Compton-thick objects. We suggest that, for all the sources, potential problems with the HEAO A-1 source identification and flux measurement prevent us from being certain that the HEAO A-1 data represent a putative "high" state for these objects. Nonetheless, based on the high flux state and Compton-thin spectrum of its GINGA observation, NGC 7674 represents probably the sixth known case of a "changing-look" Seyfert 2 galaxy. From the X-ray variability pattern, we can estimate a likely lower limit of a few parsec to the distance of the inner walls of the torus in this object. Remarkably, IRAS 13218+0552 was not detected by XMM-Newton, despite being currently classified as a Seyfert 1 with a large [OIII] flux. However, the original classification was likely to be affected by an extreme velocity outflow component in the emission lines. The object likely harbors an highly obscured AGN and should be re-classified as a type 2 source.
引用
收藏
页码:185 / 194
页数:10
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