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

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dc.contributor.authorNi, Q.
dc.contributor.authorBrandt, W. N.
dc.contributor.authorYi, W.
dc.contributor.authorLuo, B.
dc.contributor.authorTimlin, J. D., III
dc.contributor.authorHall, P. B.
dc.contributor.authorLiu, Hezhen
dc.contributor.authorPlotkin, R. M.
dc.contributor.authorShemmer, O.
dc.contributor.authorVito, F.
dc.contributor.authorWu, Jianfeng
dc.date.accessioned2025-01-23T19:51:33Z
dc.date.available2025-01-23T19:51:33Z
dc.date.issued2020
dc.description.abstractWe report the discovery of an extreme X-ray flux rise (by a factor of greater than or similar to 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.
dc.fuente.origenWOS
dc.identifier.doi10.3847/2041-8213/ab6d78
dc.identifier.eissn2041-8213
dc.identifier.issn2041-8205
dc.identifier.urihttps://doi.org/10.3847/2041-8213/ab6d78
dc.identifier.urihttps://repositorio.uc.cl/handle/11534/100586
dc.identifier.wosidWOS:000537504700002
dc.issue.numero2
dc.language.isoen
dc.revistaAstrophysical journal letters
dc.rightsacceso restringido
dc.titleAn Extreme X-Ray Variability Event of a Weak-line Quasar
dc.typeartículo
dc.volumen889
sipa.indexWOS
sipa.trazabilidadWOS;2025-01-12
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