Space Telescope and Optical Reverberation Mapping Project.VI. Reverberating Disk Models for NGC 5548

D. Starkey, K. Horne, M.~M. Fausnaugh, B.~M. Peterson, M.~C. Bentz, C.~S. Kochanek, K.~D. Denney, R. Edelson, M.~R. Goad, G. De Rosa, M.~D. Anderson, P. Arévalo, A.~J. Barth, C. Bazhaw, G.~A. Borman, T.~A. Boroson, M.~C. Bottorff, W.~N. Brandt, A.~A. Breeveld, E.~M. CackettM.~T. Carini, K.~V. Croxall, D.~M. Crenshaw, E. Dalla Bontà, A. De Lorenzo-Cáceres, M. Dietrich, N.~V. Efimova, J. Ely, P.~A. Evans, A.~V. Filippenko, K. Flatland, N. Gehrels, S. Geier, J.~M. Gelbord, L. Gonzalez, V. Gorjian, C.~J. Grier, D. Grupe, P.~B. Hall, S. Hicks, D. Horenstein, T. Hutchison, M. Im, J.~J. Jensen, M.~D. Joner, J. Jones, J. Kaastra, S. Kaspi, B.~C. Kelly, J.~A. Kennea, S.~C. Kim, M. Kim, S.~A. Klimanov, K.~T. Korista, G.~A. Kriss, J.~C. Lee, D.~C. Leonard, P. Lira, F. MacInnis, E.~R. Manne-Nicholas, S. Mathur, I.~M. McHardy, C. Montouri, R. Musso, S.~V. Nazarov, R.~P. Norris, J.~A. Nousek, D.~N. Okhmat, A. Pancoast, J.~R. Parks, L. Pei, R.~W. Pogge, J.-U. Pott, S.~E. Rafter, H.-W. Rix, D.~A. Saylor, J.~S. Schimoia, K. Schnülle, S.~G. Sergeev, M.~H. Siegel, M. Spencer, H.-I. Sung, K.~G. Teems, C.~S. Turner, P. Uttley, M. Vestergaard, C. Villforth, Y. Weiss, J.-H. Woo, H. Yan, S. Young, W. Zheng, Y. Zu

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We conduct a multiwavelength continuum variability study of the Seyfert 1 galaxy NGC 5548 to investigate the temperature structure of its accretion disk. The 19 overlapping continuum light curves ($1158\,\mathring{\rm A} $ to $9157\,\mathring{\rm A} $) combine simultaneous Hubble Space Telescope, Swift, and ground-based observations over a 180 day period from 2014 January to July. Light-curve variability is interpreted as the reverberation response of the accretion disk to irradiation by a central time-varying point source. Our model yields the disk inclination $i=36^\circ \pm 10^\circ $, temperature ${T}_{1}=(44\pm 6)\times {10}^{3}$ K at 1 light day from the black hole, and a temperature–radius slope ($T\propto {r}^{-\alpha }$) of $\alpha =0.99\pm 0.03$. We also infer the driving light curve and find that it correlates poorly with both the hard and soft X-ray light curves, suggesting that the X-rays alone may not drive the ultraviolet and optical variability over the observing period. We also decompose the light curves into bright, faint, and mean accretion-disk spectra. These spectra lie below that expected for a standard blackbody accretion disk accreting at $L/{L}_{\mathrm{Edd}}=0.1$.
Original languageEnglish
Pages (from-to)65
Number of pages1
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 18 Jan 2017


  • accretion, accretion disks, galaxies: active, galaxies: individual: NGC 5548, galaxies: nuclei, galaxies: Seyfert


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