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A wind-based unification model for NGC 5548: spectral holidays, non-disk emission, and implications for changing-look quasars

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journal contribution
posted on 2021-01-22, 15:00 authored by M Dehghanian, GJ Ferland, BM Peterson, GA Kriss, KT Korista, M Chatzikos, F Guzman, N Arav, G De Rosa, MR Goad, M Mehdipour, PAM Van hoof
The 180-day Space Telescope and Optical Reverberation Mapping campaign on NGC 5548 discovered an anomalous period, the broad-line region (BLR) holiday, in which the emission lines decorrelated from the continuum variations. This is important since the correlation between the continuum-flux variations and the emission-line response is the basic assumption for black hole (BH) mass determinations through reverberation mapping. During the BLR holiday, the high-ionization intrinsic absorption lines also decorrelated from the continuum as a result of variable covering factor of the line of sight (LOS) obscurer. The emission lines are not confined to the LOS, so this does not explain the BLR holiday. If the LOS obscurer is a disk wind, its streamlines must extend down to the plane of the disk and the base of the wind would lie between the BH and the BLR, forming an equatorial obscurer. This obscurer can be transparent to ionizing radiation, or can be translucent, blocking only parts of the SED, depending on its density. An emission-line holiday is produced if the wind density increases only slightly above its transparent state. Both obscurers are parts of the same wind, so they can have associated behavior in a way that explains both holidays. A very dense wind would block nearly all ionizing radiation, producing a Seyfert 2 and possibly providing a contributor to the changing-look AGN phenomenon. Disk winds are very common and we propose that the equatorial obscurers are too, but mostly in a transparent state.


Support for HST program number GO-13330 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.We thank NSF (1816537), NASA (ATP 17-0141), and STScI (HST-AR.13914, HST-AR-15018) for their support and Huffaker scholarship for funding the trip to Atlanta to attend the annual AGN STORM meeting, 2017. MC acknowledges support from NASA through STScI grant HST-AR14556.001-A and STScI grant HST-AR-14286, and also support from National Science Foundation through grant AST1910687. M.D. and G.F. and F. G. acknowledge support from the NSF (AST-1816537), NASA (ATP 17-0141), and STScI (HST-AR-13914, HST-AR-15018), and the Huffaker Scholarship. B.M.P. and G.D.R. are grateful for the support of the National Science Foundation through grant AST1008882 to The Ohio State University. M.M. is supported by the Netherlands Organization for Scientific Research (NWO) through the Innovational Research Incentives Scheme Vidi grant 639.042.525.



Astrophysical Journal Letters, 2019, 882 L30

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/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy


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