Multifrequency Spectra of Blazars

Abstract

BL Lacs, Highly Polarized Quasars (HPQs) and Optically Violent Variables (OVVs) are called blazars. Different types of blazars display certain similarities among them, but clear distinctions are not well known. In this paper we present the results of X-ray spectral analysis and multi-frequency (radio through X-ray) spectra of 30 blazars. HPQs/OVVs are flat spectrum and hard X-ray sources and the BL Lacs are steep spectrum and soft X-ray sources. Again, HPQs/OVVs show very steep UV spectral indices in contrast to BL Lac objects. Because of these properties HPQs/OVVs show the spectral break between UV and X-ray region (Fig. la) and it is absent in BL Lac objects (Fig. lb). Multifrequency spectra of BL Lacs and HPQs/OVVs can be fitted by using single-component and two-components power-law spectra, respectively. Luminosities of adjacent bands, in radio to UV region, show strong correlations (Figs. 2a and 2b). However, X-ray and UV luminosities do not show any correlations and radio and X-ray luminosities show bimodal nature of the distribution of blazars (Fig. 3). All these results can be explained in the frame work of a relativistically beamed pair-dominated plasma model with electrons from different regions with different energy distributions.