The broad band spectral index of blazars in a low state

Abstract

Using the broad band spectral index of 164 blazars in a low state, we studied the possible correlation between different broad band spectral index (α r.ir , α r.o , α r.x , α r.γ , α ir.o , α ir.x , α ir.γ , α o.x , α o.γ , α x.γ ). We also studied the possible correlation between different broad band spectral index of high-frequency peaked Bl Lac object (HBL), low-frequency peaked BL Lac object (LBL) and flat spectral radio quasars (FSRQs), respectively. The strong anti-correlations were found between α r.o and α o.γ , between α r.o and α x.γ in a low state for our blazar sample. For LBL and FSRQs, the strong anti-correlations were found between α r.ir and α ir.x , between α r.o and α o.x , and between α r.o and α o.γ in a low state. Based on these results, we suggested that the seed photons of the γ-ray drive from both the jet and the external accretion disk or the broad-line region, and that the subclasses of blazars seem to the different emission mechanism.