SUPERMASSIVE BLACK HOLES WITH HIGH ACCRETION RATES IN ACTIVE GALACTIC NUCLEI. IV. Hβ TIME LAGS AND IMPLICATIONS FOR SUPER-EDDINGTON ACCRETION

We have completed two years of photometric and spectroscopic monitoring of a large number of active galactic nuclei (AGNs) with very high accretion rates. In this paper, we report on the result of the second phase of the campaign, during 2013-2014, and the measurements of five new H beta time lags out of eight monitored AGNs. All five objects were identified as super-Eddington accreting massive black holes (SEAMBHs). The highest measured accretion rates for the objects in this campaign are (M) over dot(center dot) greater than or similar to 200, (M) over dot(center dot) = M over dot(center dot)/L(Edd)c(-2), (M) over dot(center dot) is the mass accretion rates, L-Edd is the Eddington luminosity and c is the speed of light. We find that the H beta time lags in SEAMBHs are significantly shorter than those measured in sub-Eddington AGNs, and the deviations increase with increasing accretion rates. Thus, the relationship between broad-line region size (R-H beta) and optical luminosity at 5100 angstrom, R-H beta-L-5100, requires accretion rate as an additional parameter. We propose that much of the effect may be due to the strong anisotropy of the emitted slim-disk radiation. Scaling R-H beta by the gravitational radius of the black hole (BH), we define a new radius-mass parameter (Y) and show that it saturates at a critical accretion rate of (M) over dot(c) = 6 similar to 30, indicating a transition from thin to slim accretion disk and a saturated luminosity of the slim disks. The parameter Y is a very useful probe for understanding the various types of accretion onto massive BHs. We briefly comment on implications to the general population of super-Eddington AGNs in the universe and applications to cosmology.