Multi-Band Spectral Properties of Fermi Blazars

摘要

The multi-band data covering optical, X-ray and γ-ray energy regions of 130 Fermi blazars in the First LAT AGN Catalog (1LAC) were collected to investigate the broadband spectral properties. The composite spectral indices show that HBLs have convex optical-to-X-ray continua and concave X-ray-to-γ-ray continua, α _(γXγ)<0 and α _(XOX) < 0, while FSRQs and LBLs have α _(γXγ) < 0. The α _(XOX) distribution of FSRQs and LBLs extends from negative to positive values. We suggest α _(γXγ) > 0 and α _(XOX) < 0 could be considered as a criterion for HBLs. Moreover, HBLs have narrow distribution of peak interval of log v _p ~(ic) - log v _p ~(syn), and FSRQs have significant anti-correlation between log v _p ~(ic) - log v _p ~(syn) and log v _p ~(syn) This indicates that SSC model is responsible for high energy emission of HBLs, while EC for FSRQs. Our results also indicate that FSRQs with larger break energy of electrons have smaller bulk Lorentz factor of dissipation region.