LONG-TERM SPECTRAL EVOLUTION OF TIDAL DISRUPTION CANDIDATES SELECTED BY STRONG CORONAL LINES

	LONG-TERM SPECTRAL EVOLUTION OF TIDAL DISRUPTION CANDIDATES SELECTED BY STRONG CORONAL LINES
	Yang, Chen-Wei 1; Wang, Ting-Gui 1; Ferland, Gary 2; Yuan, Weimin3 ; Zhou, Hong-Yan 1,4; Jiang, Peng 1
刊名	ASTROPHYSICAL JOURNAL
	2013-09-01
卷号	774 期号:1
关键词	black hole physics galaxies: nuclei line: formation
英文摘要	We present results of follow-up optical spectroscopic Multi-Mirror Telescope (MMT) observations of seven rare, extreme coronal line-emitting galaxies reported by Wang et al. Large variations in coronal lines are found in four objects, making them strong candidates for tidal disruption events (TDEs). For the four TDE candidates, all the coronal lines with ionization states higher than [Fe VII] disappear within 5-9 yr. The [Fe VII] line faded by a factor of about five in one object (J0952+2143) within 4 yr, whereas the line emerged in another two objects that previously did not show the line. A strong increment in the [O III] flux is observed, shifting the line ratios toward the loci of active galactic nuclei on the BPT diagram. Surprisingly, we detect a non-canonical [O III]lambda 5007/[O III]lambda 4959 ratio of similar or equal to 2 in two objects, indicating a large column density of O2+ and thus probably optically thick gas. This result also requires a very large ionization parameter and a relatively soft ionizing spectral energy distribution (e. g., a blackbody with T < 5 x 10(4) K). Our observations can be explained as the echoing of a strong ultraviolet to soft X-ray flare caused by TDEs on molecular clouds in the inner parsecs of the galactic nuclei. Reanalyzing the Sloan Digital Sky Survey spectra reveals double-peaked or strongly blue-shouldered broad lines in three of the objects, which disappeared in the MMT spectra of two objects and faded by a factor of 10 in 8 yr in the remaining object with a decrease in both the line width and centroid offset. We interpret these broad lines as arising from decelerating biconical outflows. Our results demonstrate that the signatures of echoing can persist for as long as 10 yr and can be used to probe the gas environment in quiescent galactic nuclei.
收录类别	SCI
语种	英语
WOS记录号	WOS:000323426700046
内容类型	期刊论文
源URL	[http://ir.bao.ac.cn/handle/114a11/5983]
专题	国家天文台_空间科学研究部
作者单位	1.Chinese Acad Sci, Univ Sci & Technol China, Key Lab Res Galaxies & Cosmol, Hefei 230026, Anhui, Peoples R China 2.Univ Kentucky, Dept Phys, Lexington, KY 40506 USA 3.Chinese Acad Sci, Natl Astron Observ, Beijing, Peoples R China 4.Polar Res Inst China, Shanghai 200136, Peoples R China
推荐引用方式 GB/T 7714	Yang, Chen-Wei,Wang, Ting-Gui,Ferland, Gary,et al. LONG-TERM SPECTRAL EVOLUTION OF TIDAL DISRUPTION CANDIDATES SELECTED BY STRONG CORONAL LINES[J]. ASTROPHYSICAL JOURNAL,2013,774(1).
APA	Yang, Chen-Wei,Wang, Ting-Gui,Ferland, Gary,Yuan, Weimin,Zhou, Hong-Yan,&Jiang, Peng.(2013).LONG-TERM SPECTRAL EVOLUTION OF TIDAL DISRUPTION CANDIDATES SELECTED BY STRONG CORONAL LINES.ASTROPHYSICAL JOURNAL,774(1).
MLA	Yang, Chen-Wei,et al."LONG-TERM SPECTRAL EVOLUTION OF TIDAL DISRUPTION CANDIDATES SELECTED BY STRONG CORONAL LINES".ASTROPHYSICAL JOURNAL 774.1(2013).