Insights on the X-ray weak quasar phenomenon from XMM–Newton monitoring of PHL1092

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dc.creator Gallo, Luigi C.
dc.creator Miniutti, G.
dc.creator Brandt, W. N.
dc.creator Schneider, D. P.
dc.creator Fabian, A. C.
dc.creator Boller, Th.
dc.date.accessioned 2015-04-24T14:56:52Z
dc.date.available 2015-04-24T14:56:52Z
dc.date.issued 2012
dc.identifier.issn 1365-2966
dc.identifier.issn 0035-8711
dc.identifier.uri http://library2.smu.ca/xmlui/handle/01/26073
dc.description Publisher's version/PDF en_CA
dc.description.abstract PHL 1092 is a z ∼ 0.4 high-luminosity counterpart of the class of Narrow-Line Seyfert 1 galaxies. In 2008, PHL 1092 was found to be in a remarkably low X-ray flux state during an XMM–Newton observation. Its 2 keV flux density had dropped by a factor of ∼260 with respect to a previous observation performed 4.5 yr earlier. The ultraviolet (UV) flux remained almost constant, resulting in a significant steepening of the optical-to-X-ray slope [alpha][subscript ox] from −1.57 to −2.51, making PHL 1092 one of the most extreme X-ray weak quasars with no observed broad absorption lines (BALs) in the UV. We have monitored the source since 2008 with three further XMM–Newton observations, producing a simultaneous UV and X-ray data base spanning almost 10 yr in total in the activity of the source. Our monitoring programme demonstrates that the [alpha][subscript ox] variability in PHL 1092 is entirely driven by long-term X-ray flux changes. We apply a series of physically motivated models with the goal of explaining the UV-to-X-ray spectral energy distribution and the extreme X-ray and [alpha][subscript ox] variability. We consider three possible models. (i) A breathing corona scenario in which the size of the X-ray-emitting corona is correlated with the X-ray flux. In this case, the lowest X-ray flux states of PHL 1092 are associated with an almost complete collapse of the X-ray corona down to the marginal stable orbit. (ii) An absorption scenario in which the X-ray flux variability is entirely due to intervening absorption. If so, PHL 1092 is a quasar with standard X-ray output for its optical luminosity, appearing as X-ray weak at times due to absorption. (iii) A disc-reflection-dominated scenario in which the X-ray-emitting corona is confined within a few gravitational radii from the black hole at all times. In this case, the intrinsic variability of PHL 1092 only needs to be a factor of ∼10 rather than the observed factor of ∼260. We discuss these scenarios in the context of non-BAL X-ray weak quasars. en_CA
dc.description.provenance Submitted by Janine Mills (janine.mills@smu.ca) on 2015-04-24T14:56:52Z No. of bitstreams: 1 Gallo_Luigi_C_article_2012_d.pdf: 1344149 bytes, checksum: 62ad8dfeeede4b9afd59647a70e05225 (MD5) en
dc.description.provenance Made available in DSpace on 2015-04-24T14:56:52Z (GMT). No. of bitstreams: 1 Gallo_Luigi_C_article_2012_d.pdf: 1344149 bytes, checksum: 62ad8dfeeede4b9afd59647a70e05225 (MD5) Previous issue date: 2012 en
dc.language.iso en en_CA
dc.publisher Royal Astronomical Society en_CA
dc.publisher Oxford University Press
dc.relation.uri http://dx.doi.org/10.1111/j.1365-2966.2012.21648.x
dc.rights This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2012 The Authors ©: 2012 RAS. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
dc.subject.lcsh Active galaxies
dc.subject.lcsh Quasars
dc.subject.lcsh X-ray sources, Galactic
dc.title Insights on the X-ray weak quasar phenomenon from XMM–Newton monitoring of PHL1092 en_CA
dc.type Text en_CA
dcterms.bibliographicCitation Monthly Notices of the Royal Astronomical Society 425(3), 1718-1737. (2012) en_CA
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This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2012 The Authors ©: 2012 RAS. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
 
Published Version: http://dx.doi.org/10.1111/j.1365-2966.2012.21648.x
 
 

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