Constraints on the location of $\gamma$-ray emitting region for a sample of blazars with radio core-shift measurements

摘要: We model simultaneous or quasi-simultaneous multi-band spectral energy distributions (SEDs) for a sample of 25 blazars that have radio core-shift measurements, where one-zone leptonic and Markov chain Monte Carlo technique are adopted. In the SED fitting 23 low-synchrotron-peaked (LSP) blazars, seed photons from broad line region (BLR) molecular torus considered respectively in external Compton process. find with better than those utilizing BLR photons, which suggests $\gamma$-ray emitting may be located outside BLR. Assuming magnetic field strength as constrained follows distribution derived measurements (i.e., $B(R)\simeq B_{\rm 1 pc}(R/\rm 1pc)^{-1}$, $R$ is distance central engine $B_{\rm pc}$ at pc), we further calculate location region, $R_{\gamma}$, these blazars. $R_{\gamma}\sim2\times10^{4}R_{\rm S}\simeq10 R_{\rm BLR}$ ($R_{\rm S}$ Schwarzschild radius $R_{\rm size), estimated luminosities using empirical correlations obtained reverberation mapping methods.