2021ApJS..253...20H

In this work, we present the first results of the long-term high-cadence spectroscopic monitoring of 15 PG quasars with relatively strong Fe II emission, as a part of a broader reverberation mapping campaign performed using the Calar Alto Observatory's 2.2 m telescope. The V-band, 5100 Å continuum, and Hβ broad emission line light curves are measured for a set of quasars for periods ranging from dozens to more than a hundred epochs between 2017 May and 2020 July. Accurate time lags between the variations of the Hβ broad-line fluxes and the optical continuum strength are obtained for all 15 quasars, ranging from 17.0_–3.2^+2.5 to 95.9_–23.9^+7.1 days in the rest frame. The virial masses of the central supermassive black holes are derived for all 15 quasars, ranging between 0.50_–0.19^+0.18 and 19.17_–2.73^+2.98 in units of 10⁷M_☉. For 11 of the objects in our sample, this is the first reverberation analysis to be published. Of the rest, two objects have been the subject of previous reverberation studies, but we determine time lags for these that are only half as long as those found in the earlier investigations, which had only been able to sample much more sparsely. The remaining two objects have previously been monitored with high sampling rates. Our results here are consistent with the earlier findings, in the sense that the time lag and the line width vary inversely, consistent with virialization.