OPTICAL MONITORING OF THE BROAD-LINE RADIO GALAXY 3C 390.3

We have undertaken a new ground-based monitoring campaign on the broad-line radio galaxy 3C 390.3 to improve the measurement of the size of the broad emission-line region and to estimate the black hole mass. This provides strong support for gravitationally bound orbital motion of the dominant part of the line-emitting gas. Combining the time delay of the strong Balmer emission lines of H[alpha] and H[beta] and the separation of the blue and red peaks in the broad double-peaked profiles in their rms spectra, we determine M super(vir) sub(bh) = 1.77 super(+0.29) sub(-0.31) x 10 super(8) M sub([middot in circle]) and using [sigma] sub(line) of the rms spectra = M super(vir) sub(bh) = 2.60 super(+0.23) sub(-0.31) x 10 super(8) M sub([middot in circle]) for the central black hole of 3C 390.3, respectively. This result is consistent with the black hole masses indicated by simple accretion disk models to describe the observed double-peaked profiles, derived from the stellar dynamics of 3C 390.3, and with the AGN radius-luminosity relation.