posted on 2016-11-21, 14:21authored byD. 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. Cackett, M. T. Carini, K. V. Croxall, D. M. Crenshaw, E. Dalla Bontà, A. De Lorenzo-Cáceres, M. Dietrich, N. V. Efimova2, 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. Pott5, 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
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 ˚A to 9157 ˚A) combine
simultaneous HST , 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◦ ± 10◦
, temperature T1 = (44 ± 6) × 103 K at 1 light day
from the black hole, and a temperature-radius slope (T ∝ r
−α) of α = 0.99±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/LEdd = 0.1.
Funding
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. D.A.S. and K.D.H.
acknowledge support from the UK Science and Technology
Facilities Council through grant ST/K502339/1
and ST/J001651/1. M.M.F., G.D.R., B.M.P., C.J.G.,
and R.W.P. are grateful for the support of the National
Science Foundation (NSF) through grant AST-1008882
to The Ohio State University. A.J.B. and L.P. have
been supported by NSF grant AST-1412693. A.V.F.
and W.Z. are grateful for financial assistance from NSF
grant AST-1211916, the TABASGO Foundation, and
the Christopher R. Redlich Fund. M.C. Bentz gratefully
acknowledges support through NSF CAREER grant
AST-1253702 to Georgia State University. M.C. Bottorff
acknowledges HHMI for support through an undergraduate
science education grant to Southwestern
University. K.D.D. is supported by an NSF Fellowship
awarded under grant AST-1302093. R.E. gratefully
acknowledges support from NASA under awards
NNX13AC26G, NNX13AC63G, and NNX13AE99G.
J.M.G. gratefully acknowledges support from NASA under
award NNX15AH49GHi Jonathan. P.B.H. is supported
by NSERC. M.I. acknowledges support from the
Creative Initiative program, No. 20080060544, of the
National Research Foundation of Korea (NRFK) funded
by the Korean government (MSIP). M.D.J. acknowledges
NSF grant AST-0618209. SRON is financially supported
by NWO, the Netherlands Organization for Scientific Research.
B.C.K. is partially supported by the UC Center
for Galaxy Evolution. C.S.K. acknowledges the support
of NSF grant AST-1515876. D.C.L. acknowledges support
from NSF grants AST-1009571 and AST-1210311.
P.L. acknowledges support from Fondecyt grant 1120328.
A.P. acknowledges support from an NSF graduate fellowship
and a UCSB Deans Fellowship. J.S.S. acknowledges
CNPq, National Council f
History
Citation
The Astrophysical Journal, 2017, 835(1)
Author affiliation
/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy