RADIATION MECHANISM AND JET COMPOSITION OF GAMMA-RAY BURSTS AND GeV-TeV-SELECTED RADIO-LOUD ACTIVE GALACTIC NUCLEI

Abstract

Gamma-ray bursts (GRBs) and GeV–TeV-selected radio-loud active galactic nuclei (AGNs) are compared based on our systematic modeling of the observed spectral energy distributions of a sample of AGNs with a single-zone leptonic model. We show that the correlation between the jet power (Pjet) and the prompt gamma-ray luminosity (Ljet) of GRBs is consistent, within the uncertainties, with the correlation between jet power and the synchrotron peak luminosity (Ls, jet) of flat spectrum radio quasars (FSRQs). Their radiation efficiencies (ε) are also comparable (>10% for most sources), which increase with the bolometric jet luminosity (Lbol, jet) for FSRQs and with the Ljet for GRBs with similar power-law indices. BL Lac objects (BL Lacs) do not follow the Pjet–Ls, jet relation of FSRQs. They have lower ε and Lbol, jet values than FSRQs, and a tentative Lbol, jet–ε relation is also found, with a power-law index different from that of the FSRQs. The magnetization parameters (σ) of FSRQs are on average larger than that of BL Lacs. They are anti-correlated with ε for the FSRQs, but positively correlated with ε for the BL Lacs. GeV narrow-line Seyfert 1 galaxies potentially share similar properties with FSRQs. Based on the analogy between GRBs and FSRQs, we suggest that the prompt gamma-ray emission of GRBs is likely produced by the synchrotron process in a magnetized jet with high radiation efficiency, similar to FSRQs. The jets of BL Lacs, on the other hand, are less efficient and are likely more matter-dominated.