Distributions of gamma-ray bursts and blazars in the Lp-Ep-plane and possible implications for their radiation physics

Abstract

We present a spectral analysis for a sample of redshift-known gamma-ray bursts (GRBs) observed with Fermi/GBM. Together with the results derived from our systematical spectral energy distribution modeling with the leptonic models for a Fermi/LAT blazar sample, we compare the distributions of the GRBs and the blazars by plotting the synchrotron peak luminosity (L<inf>s</inf>) and the corresponding peak photon energy E<inf>s</inf>of blazars in the L<inf>p</inf>-E<inf>p</inf>-plane of GRBs, where L<inf>p</inf>and E<inf>p</inf>are the peak luminosity and peak photon energy of the GRB time-integrated νf<inf>ν</inf>spectrum, respectively. The GRBs are in the high-L<inf>p</inf>, high-E<inf>p</inf>corner of the plane and a tight L<inf>p</inf>-E<inf>p</inf>relation is found, i.e., L<inf>p</inf>∝ E<inf>p</inf>^{2.13+0.54-0.46}. Both flat spectrum radio quasars (FSRQs) and low-synchrotron peaking BL Lac objects (LBLs) are clustered in the low-E<inf>p</inf>, low-L<inf>p</inf>corner. Intermediate- and high-synchrotron peaking BL Lac objects (IBLs and HBLs) have E<inf>s</inf>∼ 2 × 10^-3-10²keV and L<inf>s</inf>∼ 10⁴⁴-10⁴⁷erg s^-1, but no dependence of L<inf>s</inf>on E<inf>s</inf>is found. We show that the tight L<inf>p</inf>-E<inf>p</inf>relation of GRBs is potentially explained with the synchrotron radiation of fast-cooling electrons in a highly magnetized ejecta, and the weak anti-correlation of L<inf>s</inf>-E<inf>s</inf>for FSRQs and LBLs may be attributed to synchrotron radiation of slow-cooling electrons in a moderately magnetized ejecta. The distributions of IBLs and HBLs in the L<inf>p</inf>-E<inf>p</inf>-plane may be interpreted with synchrotron radiation of fast-cooling electrons in a matter-dominated ejecta. These results may present a unified picture for the radiation physics of relativistic jets in GRBs and blazars within the framework of the leptonic synchrotron radiation models.