(IOP Publishing, 2002) Peterson, B. M.; Berlind, Perry; Bertram, R.; Bischoff, K.; Bochkarev, N. G.; Borisov, N.; Burenkov, A. N.; Calkins, Michael; Carrasco, L.; Chavushyan, V. H.; Chornock, R; Dietrich, M.; Doroshenko, V. T.; Ezhkova, O. V.; Filippenko, A. V.; Gilbert, A. M.; Huchra, J. P.; Kollatschny, W.; Leonard, D. C.; Li, W.; Lyuty, V. M.; Malkov, Yu. F.; Matheson, T.; Merkulova, N. I.; Mikhailov, V. P.; Modjaz, M.; Onken, C. A.; Pogge, R. W.; Pronik, V. I.; Qian, B.; Romano, P.; Sergeev, S. G.; Sergeeva, E. A.; Shapovalova, A. I.; Spiridonova, O. I.; Tao, J.; Tokarz, S.; Valdes, J. R.; Vlasiuk, V. V.; Wagner, R. M.; Wilkes, Belinda
We present the final installment of an intensive 13 year study of variations of the optical continuum and broad Hβ emission line in the Seyfert 1 galaxy NGC 5548. The database consists of 1530 optical continuum measurements and 1248 Hβ measurements. The Hβ variations follow the continuum variations closely, with a typical time delay of about 20 days. However, a year-by-year analysis shows that the magnitude of emission-line time delay is correlated with the mean continuum flux. We argue that the data are consistent with the simple model prediction between the size of the broad-line region and the ionizing luminosity, r ∝ Lion. Moreover, the apparently linear nature of the correlation between the Hβ response time and the nonstellar optical continuum Fopt arises as a consequence of the changing shape of the continuum as it varies, specifically Fopt ∝ FUV.
