Broad-Line and Multi-Wave Band Emission from Blazars

Abstract

We studied the correlations of the flux of the broad-line emission ($F_{\rm BLR}$) with the X-ray emission flux, optical emission flux at 5500 ${\AA}$ and radio emission flux at 5 GHz, respectively, for a large sample of 50 blazars [39 flat-spectrum radio quasars (FSRQs) and 11 BL Lac objects]. Our main results are as follows. There are very strong correlations between $F_{\rm BLR}$ and $F_{\rm X}$ and between $L_{\rm BLR}$ and $L_{\rm X}$ in both states for 39 FSRQs, and the slopes of the linear-regression equations are almost equal to 1. There are weak correlations between $F_{\rm BLR}$ and $F_{\rm X}$ and between $L_{\rm BLR}$ and $L_{\rm X}$ for 11 BL Lac objects in both states, and the slopes of the linear-regression equations are close to 1. There are significant correlations between $F_{\rm BLR}$ and $F_{\rm X}$ and between $L_{\rm BLR}$ and $L_{\rm X}$ for 50 blazars in both states, the slopes of both linear-regression equations are also close to 1. These results support a close link between relativistic jets and accretion onto the central Kerr black hole. On the other hand, we find that BL Lac objects have a low accretion efficiency, $\eta$, whereas FSRQs have a high $\eta$. The unified model of FSRQs and BL Lac objects is also discussed.