Steps Toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei: III. Further Observations of NGC 5548 at Optical Wavelengths
Peterson B.M., et al., 1992, ApJ 392, 470

We report on the results of the second year of an intensive ground- based spectroscopic and photometric study of variability in the bright Seyfert 1 galaxy NGC 5548, which has been undertaken in order to study the relationship between continuum and emission-line variability. Relative to the first year of the monitoring program, the nucleus of NGC 5548 was considerably fainter and the continuum variations slower during the second year, but the continuum-H{beta} cross-correlation results for the two years are nearly identical. The variations in the broad H{beta} emission line lag behind those in the continuum by somewhat less than 20 days, as concluded from the first year's data.