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Title: Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the UV anomaly in NGC 5548 with X-Ray Spectroscopy
Authors: Mathur, S.
Gupta, A.
Page, K.
Pogge, R. W.
Krongold, Y.
Goad, M. R.
Adams, S. M.
Anderson, M. D.
Arévalo, P.
Barth, A. J.
Bazhaw, C.
De Rosa, G.
Dietrich, M.
Edelson, R.
Ely, J.
Grier, C. J.
Eracleous, M.
Evans, P. A.
Fausnaugh, M. M.
Ferland, G. J.
Filippenko, A. V.
Ma, Z.
Flatland, K.
Fox, O. D.
Gates, E. L.
Gehrels, N.
Geier, S.
Grupe, D.
Hall, P. B.
Henderson, C. B.
Hicks, S.
Holmbeck, E.
MacInnis, F.
Holoien, T. W.-S.
Netzer, H.
Horenstein, D.
Horne, Keith
Hutchison, T.
Im, M.
Jensen, J. J.
Johnson, C. A.
Joner, M. D.
Jones, J.
Manne-Nicholas, E. R.
Kaastra, J.
Kaspi, S.
Nguyen, M. L.
Kelly, B. C.
Kelly, P. L.
Kennea, J. A.
Kim, M.
Kim, S.
Kim, S. C.
King, A.
Malkan, M. A.
Klimanov, S. A.
Kochanek, C. S.
Korista, K. T.
Norris, R. P.
Kriss, G. A.
Lau, M. W.
Lee, J. C.
Leonard, D. C.
Li, M.
Lira, P.
Nousek, J. A.
Mauerhan, J. C.
McGurk, R.
McHardy, I. M.
Montouri, C.
Morelli, L.
Uttley, P.
Mosquera, A.
Mudd, D.
Muller-Sanchez, F.
Musso, R.
Nazarov, S. V.
Ochner, P.
Okhmat, D. N.
Ou-Yang, B.
Pancoast, A.
Papadakis, I.
Van Saders, J.
Parks, J. R.
Beatty, T. G.
Pei, L.
Peterson, B. M.
Pizzella, A.
Poleski, R.
Pott, J.-U.
Rafter, S. E.
Rix, H.-W.
Runnoe, J.
Vestergaard, M.
Saylor, D. A.
Schimoia, J. S.
Bentz, M. C.
Schnülle, K.
Sergeev, S. G.
Shappee, B. J.
Shivvers, I.
Siegel, M.
Simonian, G. V.
Siviero, A.
Vican, L.
Skielboe, A.
Somers, G.
Spencer, M.
Bigley, A.
Starkey, D.
Stevens, D. J.
Sung, H.-I.
Tayar, J.
Tejos, N.
Turner, C. S.
Bisogni, S.
Villanueva Jr., S.
Villforth, C.
Weiss, Y.
Woo, J.-H.
Yan, H.
Gelbord, J. M.
Young, S.
Yuk, H.
Zheng, W.
Zhu, W.
Zu, Y.
Borman, G. A.
Boroson, T. A.
Bottorff, M. C.
Brandt, W. N.
Breeveld, A. A.
Gorjian, V.
Brown, J. E.
Brown, J. S.
Cackett, E. M.
Canalizo, G.
Carini, M. T.
Clubb, K. I.
Comerford, J. M.
Coker, C. T.
Corsini, E. M.
Crenshaw, D. M.
Greene, J. E.
Croft, S.
Croxall, K. V.
Dalla Bontà, E.
Deason, A. J.
Denney, K. D.
De Lorenzo-Cáceres, A.
First Published: 31-Aug-2017
Publisher: American Astronomical Society, IOP Publishing
Citation: Astrophysical Journal, 2017, 846:55
Abstract: During the Space Telescope and Optical Reverberation Mapping Project (STORM) observations of NGC 5548, the continuum and emission-line variability became decorrelated during the second half of the 6-month long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as a part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide the Swift data into on- and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than being due to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. This model simultaneously explains all the three observations: the UV emission line flux decrease, the soft-excess increase, and the emission line anomaly.
DOI Link: 10.3847/1538-4357/aa832b
ISSN: 0004-637X
eISSN: 1538-4357
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright ©2017, American Astronomical Society, IOP Publishing. Deposited with reference to the publisher’s open access archiving policy.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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