COMPTONIZATION IN SUPER-EDDINGTON ACCRETION FLOW AND GROWTH TIMESCALE OF SUPERMASSIVE BLACK HOLES

摘要

Super-Eddington accretion onto black holes (BHs) may occur at ultraluminous compact X-ray sources in nearby galaxies, Galactic microquasars, and narrow-line Seyfert 1 galaxies (NLS1s). Effects of electron scattering (opacity and Comptonization) and the relativistic correction (gravitational redshift and transverse Doppler effect) on the emergent spectra from super-Eddington accretion flows onto non-rotating BHs are examined for 10~(1.5) and 10~(6.5) solar mass BH masses (M_(BH)). With m[≡ M/(L_(Edd)/c~2)] ≥ 100 (where M is the accretion rate), the spectral hardening factor via electron scattering is approx< 2.3-6.5. As a result of the m-sensitive hardening factor, the color temperature of the innermost radiation is not proportional to L~(0.25), differing from the simplest standard accretion disk. The model is applied to optical-soft X-ray emission from NLS1s. We pick up one NLS1, namely, PG 1448+273 with an inferred M_(BH) of 10~(6.4) solar mass, among the highest m candidates. The broadband spectral distribution is successfully reproduced by the model with an extremely high m (=1000) and the viscosity parameter a of 0.01. This implies that this object, as well as some other highest m systems, is really young: the inferred age, M_(BH)/M, is about 10~6 yr. We also briefly discuss the distribution of m for transient and highly variable NLS1s, finding that those are located at 3 appros