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dc.contributor.authorDehghanian, M.
dc.contributor.authorFerland, G. J.
dc.contributor.authorKriss, G. A.
dc.contributor.authorPeterson, B. M.
dc.contributor.authorMathur, S.
dc.contributor.authorMehdipour, M.
dc.contributor.authorGuzmán, F.
dc.contributor.authorChatzikos, M.
dc.contributor.authorvan Hoof, P. A. M.
dc.contributor.authorWilliams, R. J. R.
dc.contributor.authorArav, N.
dc.contributor.authorBarth, A. J.
dc.contributor.authorBentz, M. C.
dc.contributor.authorBisogni, S.
dc.contributor.authorBrandt, W. N.
dc.contributor.authorCrenshaw, D. M.
dc.contributor.authorBontà, E. Dalla
dc.contributor.authorDe Rosa, G.
dc.contributor.authorFausnaugh, M. M.
dc.contributor.authorGelbord, J. M.
dc.contributor.authorGoad, M. R.
dc.contributor.authorGupta, A.
dc.contributor.authorHorne, Keith
dc.contributor.authorKaastra, J.
dc.contributor.authorKnigge, C.
dc.contributor.authorKorista, K. T.
dc.contributor.authorMcHardy, I. M.
dc.contributor.authorPogge, R. W.
dc.contributor.authorStarkey, D. A.
dc.contributor.authorVestergaard, M.
dc.date.accessioned2019-10-02T23:17:17Z
dc.date.available2019-10-02T23:17:17Z
dc.date.issued2019-06-03
dc.identifier.citationM. Dehghanian et al 2019 ApJ 877 119en_US
dc.identifier.issn0004-637X
dc.identifier.doi10.3847/1538-4357/ab1b48
dc.identifier.urihttp://hdl.handle.net/10150/634667
dc.description.abstractThe Space Telescope and Optical Reverberation Mapping Project (AGN STORM) on NGC 5548 in 2014 is one of the most intensive multiwavelength AGN monitoring campaigns ever. For most of the campaign, the emission-line variations followed changes in the continuum with a time lag, as expected. However, the lines varied independently of the observed UV-optical continuum during a 60-70 day "holiday," suggesting that unobserved changes to the ionizing continuum were present. To understand this remarkable phenomenon and to obtain an independent assessment of the ionizing continuum variations, we study the intrinsic absorption lines present in NGC 5548. We identify a novel cycle that reproduces the absorption line variability and thus identify the physics that allows the holiday to occur. In this cycle, variations in this obscurer's line-of-sight covering factor modify the soft X-ray continuum, changing the ionization of helium Ionizing radiation produced by recombining helium then affects the level of ionization of some ions seen by the Hubble Space Telescope. In particular, high-ionization species are affected by changes in the obscurer covering factor, which does not affect the optical or UV continuum, and thus appear as uncorrelated changes, a "holiday." It is likely that any other model that selectively changes the soft X-ray part of the continuum during the holiday can also explain the anomalous emission-line behavior observed.en_US
dc.description.sponsorshipNASA through a grant from the Space Telescope Science Institute [NNX15AH49G, 80NSSC17K0126, NAS5-26555]; NSF [1816537, AST-1816537, AST-1412693, AST-1009756, AST-1412315]; NASA [NNX15AH49G, 80NSSC17K0126, ATP 17-0141, AR7-18013X, NAS8-03060, PF5-160141]; STScI [HST-AR.13914, HST-AR-15018]; NASA through STScI grant [HST-AR-14556.001A, HST-AR-14286]; Huffaker Scholarship; National Science Foundation [AST-1008882]; NSF CAREER [AST-1253702]; Padua University [DOR1699945/16, DOR1715817/17, DOR1885254/18, BIRD164402/16]; NSF Fellowship award [AST-1302093]; STFC [ST/R000824/1, ST/M001326/1]; NWO; Netherlands Organization for Scientific Research; Packard Foundation; Danish Council [DFF 4002-00275]; Royal Society Leverhulme Trust Senior Research Fellowship [LT160006]; [HST-AR-13240.009]en_US
dc.language.isoenen_US
dc.publisherIOP PUBLISHING LTDen_US
dc.rightsCopyright © 2019. The American Astronomical Society. All rights reserved.en_US
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/
dc.subjectgalaxies: activeen_US
dc.subjectgalaxies: individual (NGC 5548)en_US
dc.subjectgalaxies: nucleien_US
dc.subjectgalaxies: Seyferten_US
dc.subjectline: formationen_US
dc.titleSpace Telescope and Optical Reverberation Mapping Project. X. Understanding the Absorption-line Holiday in NGC 5548en_US
dc.typeArticleen_US
dc.contributor.departmentUniv Arizona, Steward Observen_US
dc.identifier.journalASTROPHYSICAL JOURNALen_US
dc.description.collectioninformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.en_US
dc.eprint.versionFinal published versionen_US
dc.source.volume877
dc.source.issue2
dc.source.beginpage119
refterms.dateFOA2019-10-02T23:17:18Z


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