UNIQUE BROAD-LINE PROFILE VARIATIONS IN THE RADIO GALAXY 3C-390.3

We report the results of a variability study of the flux and profile of H-beta in 3C 390.3. Spectra of this object were obtained at 39 epochs during the years 1974-1988. We show that the fluctuations of the H-beta-flux closely mimic the variations of the optical continuum during that period. The time scale for the emission-line variations is shorter than a year, and perhaps as short as a month. We note that the blue side of the H-beta-profile ("blue bump") also followed closely the continuum variations, but the red side ("red bump") did not. The ratio of the fluxes of the blue and red bumps behaved in a very regular, nearly sinusoidal fashion. It reached a maximum in mid-1975 and at the end of 1985, a time interval of 10.4 yr. The velocity of the peak of the blueshifted bump drifted by +900 km s-1 during the 14 yr interval covered by the observations. Another emission feature at a velocity of +4600 km s-1 relative to systemic velocity was visible in the broad-line profiles of 1974-1975. Various scenarios are proposed to explain these results. The more successful models are those involving an inhomogeneous line-emitting disk or a biconical broad-line region.