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

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_s) and the corresponding peak photon energy E_sof blazars in the L_p-E_p-plane of GRBs, where L_pand E_pare the peak luminosity and peak photon energy of the GRB time-integrated νf_νspectrum, respectively. The GRBs are in the high-L_p, high-E_pcorner of the plane and a tight L_p-E_prelation is found, i.e., L_p∝ E_p^{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_p, low-L_pcorner. Intermediate- and high-synchrotron peaking BL Lac objects (IBLs and HBLs) have E_s∼ 2 × 10^-3-10²keV and L_s∼ 10⁴⁴-10⁴⁷erg s^-1, but no dependence of L_son E_sis found. We show that the tight L_p-E_prelation 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_s-E_sfor 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_p-E_p-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.