Blazar Black Hole Masses

Black hole mass, along with the ratio of the accretionrate to the Eddington accretion rate, is a fundamental parameter of active galactic nuclei (AGNs).Using Xie's method of the black mass estimate, we developed our sample and estimated the black hole masses represented by M_H for 21 blazars.We compare 21cases for each of which the relevant black hole mass has been also estimated by the MBH-_σ correlation method, which is represented by M_σ.And we find that (1)M_H are systematically lower thanM_σ, but the differences between M_σ and M_H are very small for most of the sources;(2)there is a significant correlation between M_σ and M_H, the correlation coefficient r=0.823 with chance probability p~1.0×10^-4.Based on these properties mentioned above and the standard model of AGNs, we prove that the nature of the systematical difference between M_σ and M_H is that M_σ represents the mass in broad emission line region (r≤rb), while M_H represents the mass in the continual emission region (r≤ra and ra rb)which is near the innermost stable orbit around the black hole.That is, M_σwould be overestimated.From M_σ, we calculate the central black hole mass again, which is indicated by M_H^*, and find that M_H^* is almost equal to the correspondent M_H.