Continuum Reverberation Mapping of the Accretion Disks in Two Seyfert 1 Galaxies

Author(s): Fausnaugh, MM; Starkey, DA; Horne, K; Kochanek, CS; Peterson, BM; Bentz, MC; Denney, KD; Grier, CJ; Grupe, D; Pogge, RW; De Rosa, G; Adams, SM; Barth, AJ; Beatty, TG; Bhattacharjee, A; Borman, GA; Boroson, TA; Bottorff, MC; Brown, JE; Brown, JS; Brotherton, MS; Coker, CT; Crawford, SM; Croxall, KV; Eftekharzadeh, S; Eracleous, M; Joner, MD; Henderson, CB; Holoien, TWS; Hutchison, T; Kaspi, S; Kim, S; King, AL; Li, M; Lochhaas, C; Ma, Z; Macinnis, F; Manne-Nicholas, ER; Mason, M; Montuori, C; Mosquera, A; Mudd, D; Musso, R; Nazarov, SV; Nguyen, ML; Okhmat, DN; Onken, CA; Ou-Yang, B; Pancoast, A; Pei, L; Penny, MT; Poleski, R; Rafter, S; Romero-Colmenero, E; Runnoe, J; Sand, DJ; Schimoia, JS; Sergeev, SG; Shappee, BJ; Simonian, GV; Somers, G; Spencer, M; Stevens, DJ; Tayar, J; Treu, T; Valenti, S; Van Saders, J; Villanueva, S; Villforth, C; Weiss, Y; Winkler, H; Zhu, W | Abstract: © 2018. The American Astronomical Society. All rights reserved.. We present optical continuum lags for two Seyfert 1 galaxies, MCG+08-11-011 and NGC 2617, using monitoring data from a reverberation mapping campaign carried out in 2014. Our light curves span the ugriz filters over four months, with median cadences of 1.0 and 0.6 days for MCG+08-11-011 and NGC 2617, respectively, combined with roughly daily X-ray and near-UV data from Swift for NGC 2617. We find lags consistent with geometrically thin accretion-disk models that predict a lag-wavelength relation of τ ∝ λ 4/3. However, the observed lags are larger than predictions based on standard thin-disk theory by factors of 3.3 for MCG+08-11-011 and 2.3 for NGC 2617. These differences can be explained if the mass accretion rates are larger than inferred from the optical luminosity by a factor of 4.3 in MCG+08-11-011 and a factor of 1.3 in NGC 2617, although uncertainty in the SMBH masses determines the significance of this result. While the X-ray variability in NGC 2617 precedes the UV/optical variability, the long (2.6 day) lag is problematic for coronal reprocessing models.