The Jet-Disk Symbiosis in Blazar and Unified Model of FSRQs and BL Lac Objects

Abstract

Using multi-wave band data for a large sample of 70 blazars, including 38 flat-spectrum radio quasars (FSRQs) and 32 BL Lac Objeces, we studied the correlations for both the flux and luminosity of the broad-line emission ($F_{\rm BLR}$) with the near-infrared flux ($F_{K}$), X-ray flux ($F_{X}$) and radio flux at 5 GHz ($F_{R}$), respectively. We could see that there is always a strong correlation between the broad-line and multi-wave bands for a sample of 70 blazars; also, the slopes of the corresponding linear-regression equations are close to 1, which is consistent with the theoretical results. These results provide some new experimental evidence about coupling of the accretion disk and the jet of blazars. Simultaneously, we also indicated that the relative location of BL Lacs and FSRQs are quite separated, and that the luminosity of the the broad-line emission for BL Lacs is much less for FSRQs, which can prove that FSRQs and BL Lacs could be considered as a single population, or FSRQs and BL Lacs should be regarded as a class. But they are in different evolutionary stages of blazars, and have different types of accretion disks with different line-to-continuum ratios. Finally, the unified model of FSRQs and BL Lacs is also discussed.