Jet power extracted from ADAFs and the application to Fermi BL Lacertae objects

Abstract

We calculate the jet power of the Blandford–Znajek (BZ) model and the hybrid model based on the self-similar solution of advection-dominated accretion flows (ADAFs). We study the formation mechanism of the jets of BL Lacertae (BL Lacs) with known redshifts detected by the Fermi satellite after 10 yr of data (4FGL-DR2). The kinetic power of the jets of Fermi BL Lacs is estimated through radio luminosity. The main results are as follows. (1) We find that the jet kinetic power of about 72 per cent intermediate peak frequency BL Lacs (IBL) and 94 per cent high-frequency peak BL Lacs (HBL) can be explained by the hybrid jet model based on ADAFs surrounding Kerr black holes. However, the jet kinetic power of about 74 per cent low-frequency peak BL Lacs (LBL) cannot be explained by the BZ jet model or the hybrid model. (2) The LBL has a higher accretion rate than IBL and HBL. About 14 per cent IBL and 62 per cent HBL have pure optically thin ADAFs. However, 7 per cent LBL may have a hybrid structure consisting of an standard thin disc (SS) plus optically thin ADAFs. (3) After excluding the redshift dependence, there is a weak correlation between the jet kinetic power and the accretion disc luminosity for Fermi BL Lacs. (4) There is a significant correlation between inverse-Compton luminosity and synchrotron luminosity for Fermi BL Lacs. The slope of the relation between inverse-Compton luminosity and synchrotron luminosity for Fermi BL Lacs is consistent with the synchrotron self-Compton (SSC) process. The result may suggest that the high-energy components of Fermi BL Lacs are dominated by the SSC process.