Space Telescope and Optical Reverberation Mapping Project VI: reverberating Disk Models for NGC 5548

Abstract

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 to 9157 angstroms) 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, temperature T1 at 1 light day from the black hole, and a temperature-radius slope, alpha. 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

V2: Oops wrong title! V1: Accepted for publication in ApJ, 20 Pages, 11 Figures

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• X-ray reverberation around accreting black holes
• Testing thermal reprocessing in AGN accretion discs
• A fast and long-lived outflow from the supermassive black hole in NGC 5548
• Sizes and Temperature Profiles of Quasar Accretion Disks from Chromatic Microlensing
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