Constraining the black hole mass and accretion rate in the narrow-line Seyfert 1 galaxy RE J1034+396

We present a comprehensive study of the spectrum of the narrow-line Seyfert 1 (NLS1) galaxy RE J1034+396, summarizing the information obtained from th e optical to X-rays with observations from the William Herschel 4.2 m Teles cope, the Hubble Space Telescope, the Extreme Ultraviolet Explorer, ROSAT, ASCA, and BeppoSAX. The BeppoSAX spectra reveal a soft component which is w ell represented by two blackbodies with kT(eff) = 60 and 160 eV, mimicking that expected from a hot, optically thick accretion disk around a low-mass black hole. This is borne out by our modeling of the optical-to- X-ray nucl ear continuum, which constrains the physical parameters of a NLS1 for the f irst time. The models demonstrate that RE J1034+396 is likely to be a syste m with a nearly edge-on accretion disk (60 degrees -75 degrees from the dis k axis), accreting at nearly Eddington rates (0.3-07L(Edd)) onto a low-mass black hole (M-bh similar to 2-10 x 10(6) M.). This is consistent with the hypothesis that NLS1s are Seyfert-scale analogies of galactic black hole ca ndidates. The unusually high temperature of the big blue bump reveals a fla t power-law-like continuum in the optical/UV which is consistent with an ex trapolation to the hard X-ray power law, and which we speculate may be simi lar to the continuum component observed in BL Lac objects in their quiescen t periods. From the BeppoSAX and ASCA data, we find that the slope of the h ard X-ray power law depends very much on the form of the soft component whi ch is assumed. For our best-fitting models, it lies somewhere between alpha = 0.7 and 1.3 and thus may not be significantly softer than active galacti c nuclei in general.