We present the light curves obtained during an eight-year program of optical spectroscopic monitoring of nine Seyfert 1 galaxies: 3C 120, Akn 120, Mrk 79, Mrk 110, Mrk 335, Mrk 509, Mrk 590, Mrk 704, and Mrk 817. All objects show significant variability in both the continuum and emission-line fluxes. We use cross-correlation analysis to derive the sizes of the broad Hβ-emitting regions based on emission-line time delays, or lags. We successfully measure time delays for eight of the nine sources, and find values ranging from about two weeks to a little over two months. Combining the measured lags and widths of the variable parts of the emission lines allows us to make virial mass estimates for the active nucleus in each galaxy. The virial masses are in the range 10 7−8 M ⊙ .

We present results of an intensive 2 month campaign of ground-based spectrophotometric monitoring of the Seyfert 1 galaxy NGC 7469, with a temporal resolution day. The broad Ha and Hb emission [ 1 lines respond to D35% ultraviolet continuum variations with an amplitude of D10% and time delays of 5.6^1.3 days and 5.4^0.8 days, respectively. We interpret this as evidence of variable Balmer line gas D5È6 light days from the central source in this object, widely believed to be a supermassive black hole. The virial mass of the central source implied by line widths and time delays is D106È107 Concomi-M _. tantly, we Ðnd evidence for wavelength-dependent continuum time delays : optical continuum variations lag those at 1315 by 1.0^0.3 days at 4865 to 1.5^0.7 days at 6962 This suggests a stratiÐed A A A. continuum reprocessing region extending several light days from the central source, possibly an accretion disk.

We report on the results of a three-year program of coordinated X-ray and optical monitoring of the narrow-line Seyfert 1 galaxy NGC 4051. The rapid continuum variations observed in the X-ray spectra are not detected in the optical, although the time-averaged X-ray and optical continuum fluxes are well-correlated. Variations in the flux of the broad Hβ line are found to lag behind the optical continuum variations by 6 days (with an uncertainty of 2-3 days), and combining this with the line width yields a virial mass estimate of ∼ 1.1 × 10 6 M ⊙ , at the very low end of the distribution of AGN masses measured by line reverberation. Strong variability of He ii λ4686 is also detected, and the response time measured is similar to that of Hβ, but with a much larger uncertainty. The He ii λ4686 line is almost five times broader than Hβ, and it is strongly blueward asymmetric, as are the high-ionization UV lines recorded in archival spectra of NGC 4051. The data are consistent with the Balmer lines arising in a low to moderate inclination disk-like configuration, and the high-ionization lines arising in an outflowing wind, of which we observe preferentially the near side. Previous observations of the narrow-line region morphology of this source suggest that the system is inclined by ∼ 50 o , and if this is applicable to the broad Hβ-emitting region, a central mass of ∼ 1.4 × 10 6 M ⊙ can be inferred. During the third year of monitoring, both the X-ray continuum and the He ii λ4686 line went into extremely low states, although the optical continuum and the Hβ broad line were both still present and 6 Deceased.-2variable. We suggest that the inner part of the accretion disk may have gone into an advection-dominated state, yielding little radiation from the hotter inner disk.2. NLS1s are low-inclination (i.e., nearly face-on) systems (Osterbrock & Pogge 1985). In this model, the line widths are again due to orbital motion around the central black hole, and the bulk of the broad-line region (BLR) gas orbits in a common plane that is almost perpendicular to the line of sight, leading to relatively small Doppler widths.3. NLS1s have relatively low black-hole masses, but high accretion rates. Again, the basic assumption is that the BLR motions are virial, but the central source has a lower mass. The luminosity can be kept relatively high by supposing that the accretion rate (relative to the Eddington rate) is correspondingly high in these sources.