SIMBAD references

Using a sample of 208 broad-line active galactic nuclei (AGNs) from the Swift/BAT AGN Spectroscopic Survey in the ultra-hard X-ray band (14-195 keV), the hot corona properties are investigated, i.e. the fraction of gravitational energy dissipated in the hot corona and the hard X-ray photon index. The bolometric luminosity, L_Bol, is calculated from host-corrected luminosity at 5100 Å. Virial supermassive black-hole masses (SMBH, M_BH) are calculated from the Hβline width and the corresponding broad-line region size-luminosity empirical relation at 5100 Å. We find a strong anti-correlation between the fraction of energy released in corona (F_X ≡ L_14–195keV/L_Bol) and the Eddington ratio (ε ≡ L_Bol/L_Edd), F_X ∝ ε^–0.60±0.1. It is found that this fraction also has a correlation with the SMBH mass, F_ X_ ∝ε^-0.74±0.14^ M_ BH_^-0.30±0.03^. Assuming that magnetic buoyancy and field reconnection lead to the formation of a hot corona, our result favours the shear stress tensor being a proportion of the gas pressure. For our entire sample, it is found that the hard X-ray photon index Γ has a weak but significant correlation with the Eddington ratio, Γ = 2.17 + 0.21log ε. However, this correlation is not robust because the relation is not statistically significant for its subsample of 32 reverberation-mapping AGNs with relatively reliable M_BH or its subsample of 166 AGNs with single-epoch M_BH. We do not find a statistically significant relation between the photon index and the Eddington ratio taking into account an additional dependence on F_X.