An Extreme X-Ray Variability Event of a Weak-line Quasar
Ni,Q.1,2; Brandt,W. N.1,2,3; Yi,W.1,4,5; Luo,B.6,7,8; Timlin,J. D.1,2; Hall,P. B.9; Liu,Hezhen6,7,8; Plotkin,R. M.10; Shemmer,O.11; Vito,F.12,13; Wu,Jianfeng14
Source PublicationThe Astrophysical Journal Letters
AbstractAbstract 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.
KeywordX-ray active galactic nuclei Active galaxies Quasars X-ray quasars Radio quiet quasars X-ray sources
WOS IDIOP:2041-8205-889-2-ab6d78
PublisherThe American Astronomical Society
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Document Type期刊论文
Affiliation1.Department of Astronomy & Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802, USA;
2.Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA
3.Department of Physics, The Pennsylvania State University, University Park, PA 16802, USA
4.Yunnan Observatories, Kunming, 650216, People's Republic of China
5.Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650216, People's Republic of China
6.School of Astronomy and Space Science, Nanjing University, Nanjing, Jiangsu 210093, People's Republic of China
7.Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing, Jiangsu 210093, People's Republic of China
8.Collaborative Innovation Center of Modern Astronomy and Space Exploration, Nanjing 210093, People's Republic of China
9.Department of Physics & Astronomy, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada
10.Department of Physics, University of Nevada, 1664 N. Virginia Street, Reno, NV 89557, USA
11.Department of Physics, University of North Texas, Denton, TX 76203, USA
12.Instituto de Astrofísica and Centro de Astroingeniería, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
13.Chinese Academy of Sciences South America Center for Astronomy, National Astronomical Observatories, CAS, Beijing 100012, People's Republic of China
14.Department of Astronomy, Xiamen University, Xiamen, Fujian 361005, People's Republic of China
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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).
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