The Nature of the High-energy γ-Ray Radiation Associated with the High-redshift Blazar B3 1343+451

Abstract High-redshift blazars are the most powerful extragalactic astrophysical sources ever detected in the high-energy γ -ray band. In this study, we present a temporal and spectral analysis of the high-redshift blazar B3 1343+451 based on 14 yr of the Fermi Large Area Telescope observations, spanning from 2008 August 4 to 2022 June 6 (MJD = 54686–59733). We extract a 7 day binned γ -ray light curve in the energy range 0.1–500 GeV and identify seven outburst periods with a peak flux of >4.32 × 10 −7 ph cm −2 s −1 . The highest 7 day flux (above 100 MeV) reaches (8.06 ± 0.56) × 10 −7 erg cm −2 s −1 on MJD = 56177.16, which is 10 times higher than the flux in the quiescent period. To understand the properties of distant blazar jets, we employ a standard one-zone leptonic scenario and model the multiwavelength spectral energy distributions of one quiescent and seven flaring periods. We find that the γ -ray spectrum is better reproduced when the dissipation region of the jet, R diss , is located within the molecular torus, where infrared emission is the dominant external photon field. We infer that the jets in higher-redshift blazars have larger power and kinetic energy, where the kinetic energy is significantly greater than the radiation power, and the jet production efficiency suggests that we need to lower the accretion efficiency. These results imply that B3 1343+451 may have a standard thin disk surrounding its massive black hole, and the jets of B3 1343+451 may not be fully explained by the Blandford–Payne process.