Discovery of high-amplitude X-ray variability in the Seyfert-LINER transition galaxy NGC 7589

	Discovery of high-amplitude X-ray variability in the Seyfert-LINER transition galaxy NGC 7589
	Yuan, W; Komossa, S ; Xu, D; Osborne, JP ; Watson, MG ; McMahon, RG
刊名	MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
	2004-09-21
卷号	353 期号:3 页码:L29-L33
关键词	galaxies : active galaxies : individual : NGC 7589 X-ray : galaxies
英文摘要	We present the first result of a programme to search for large flux variations in the X-ray sources of the XMM Serendipitous Survey compared to previous ROSAT observations. An increase in X-ray flux by a factor >10 was discovered from the nucleus of the galaxy NGC7589 on a time-scale of less than 5 yr. The 0.4-10 keV XMM spectrum can be approximated by a power law with photon index of 1.7-1.8, though it seems to flatten above 5 keV, suggesting a possible complex model, such as partial covering or disc reflection. A classification based on an analysis of its optical spectrum places NGC 7589 in the Seyfert region, but close to the Seyfert-LINER (low-ionization nuclear emission-line region) borderline on the active galactic nucleus (AGN) diagnostic diagrams. We classify NGC 7589 as either Seyfert 1.9 or LINER I, in the light of the detection of a broad Halpha line, which makes NGC 7589 an AGN in the low-luminosity regime. We interpret the observed variability in terms of either changes in covering factor of absorbing gas in the AGN, or variability in the intrinsic X-ray luminosity. Should the latter be the case, the inferred Eddington accretion rate increased from the radiatively inefficient accretion-dominated regime to a value close to the putative critical value, at which a transition of the accretion mode is supposed to take place. This possibility presents a new prospect of studying accretion physics in the central black holes of external galaxies by direct observing changes of 'spectral state', as is common in stellar black hole binary systems.
收录类别	SCI
语种	英语
WOS记录号	WOS:000224300700002
内容类型	期刊论文
源URL	[http://ir.bao.ac.cn/handle/114a11/6955]
专题	国家天文台_空间科学研究部
作者单位	1.Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England 2.Max Planck Inst Extraterr Phys, D-85741 Garching, Germany 3.Chinese Acad Sci, Natl Astron Observ, Beijing 100012, Peoples R China 4.Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England
推荐引用方式 GB/T 7714	Yuan, W,Komossa, S,Xu, D,et al. Discovery of high-amplitude X-ray variability in the Seyfert-LINER transition galaxy NGC 7589[J]. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY,2004,353(3):L29-L33.
APA	Yuan, W,Komossa, S,Xu, D,Osborne, JP,Watson, MG,&McMahon, RG.(2004).Discovery of high-amplitude X-ray variability in the Seyfert-LINER transition galaxy NGC 7589.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY,353(3),L29-L33.
MLA	Yuan, W,et al."Discovery of high-amplitude X-ray variability in the Seyfert-LINER transition galaxy NGC 7589".MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 353.3(2004):L29-L33.