An Extreme X-Ray Variability Event of a Weak-line Quasar

doi:10.3847/2041-8213/ab6d78

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	An Extreme X-Ray Variability Event of a Weak-line Quasar
	Ni,Q.7,8; Brandt,W. N.7,8,9; Yi,W.7,10,11; Luo,B.12,13,14; Timlin,J. D.7,8; Hall,P. B.1; Liu,Hezhen 12,13,14; Plotkin,R. M.2; Shemmer,O.3; Vito,F.4,6
刊名	The Astrophysical Journal Letters
	2020-02-01
卷号	889 期号:2
关键词	X-ray active galactic nuclei Active galaxies Quasars X-ray quasars Radio quiet quasars X-ray sources
ISSN号	2041-8205
DOI	10.3847/2041-8213/ab6d78
英文摘要	Abstract We report the discovery of an extreme X-ray flux rise (by a factor of ?20) of the weak-line quasar Sloan Digital Sky Survey (SDSS) J153913.47+395423.4 (hereafter SDSS J1539+3954) at z?=?1.935. SDSS J1539+3954 is the most-luminous object among radio-quiet type?1 active galactic nuclei (AGNs) where such dramatic X-ray variability has been observed. Before the X-ray flux rise, SDSS J1539+3954 appeared X-ray weak compared with the expectation from its ultraviolet (UV) flux; after the rise, the ratio of its X-ray flux and UV flux is consistent with the majority of the AGN population. We also present a contemporaneous HET spectrum of SDSS J1539+3954, which demonstrates that its UV continuum level remains generally unchanged despite the dramatic increase in the X-ray flux, and its C?iv emission line remains weak. The dramatic change only observed in the X-ray flux is consistent with a shielding model, where a thick inner accretion disk can block our line of sight to the central X-ray source. This thick inner accretion disk can also block the nuclear ionizing photons from reaching the high-ionization broad emission-line region, so that weak high-ionization emission lines are observed. Under this scenario, the extreme X-ray variability event may be caused by slight variations in the thickness of the disk. This event might also be explained by gravitational light-bending effects in a reflection model.
语种	英语
出版者	The American Astronomical Society
WOS记录号	IOP:2041-8205-889-2-AB6D78
内容类型	期刊论文
源URL	[http://ir.bao.ac.cn/handle/114a11/53992]
专题	中国科学院国家天文台
作者单位	1.Department of Physics & Astronomy, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada 2.Department of Physics, University of Nevada, 1664 N. Virginia Street, Reno, NV 89557, USA 3.Department of Physics, University of North Texas, Denton, TX 76203, USA 4.Instituto de Astrofísica and Centro de Astroingeniería, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile 5.Department of Astronomy, Xiamen University, Xiamen, Fujian 361005, People's Republic of China 6.Chinese Academy of Sciences South America Center for Astronomy, National Astronomical Observatories, CAS, Beijing 100012, People's Republic of China 7.Department of Astronomy & Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802, USA; qxn1@psu.edu 8.Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA 9.Department of Physics, The Pennsylvania State University, University Park, PA 16802, USA 10.Yunnan Observatories, Kunming, 650216, People's Republic of China
推荐引用方式 GB/T 7714	Ni,Q.,Brandt,W. N.,Yi,W.,et al. An Extreme X-Ray Variability Event of a Weak-line Quasar[J]. The Astrophysical Journal Letters,2020,889(2).
APA	Ni,Q..,Brandt,W. N..,Yi,W..,Luo,B..,Timlin,J. D..,...&Wu,Jianfeng.(2020).An Extreme X-Ray Variability Event of a Weak-line Quasar.The Astrophysical Journal Letters,889(2).
MLA	Ni,Q.,et al."An Extreme X-Ray Variability Event of a Weak-line Quasar".The Astrophysical Journal Letters 889.2(2020).