A Multiwavelength Study of Distant Blazar PKS 0537-286

Abstract

We report the results of broadband observations of distant blazar PKS 0537-286 (z = 3.1) using data spanning more than ten years from the Fermi Large Area Telescope together with Swift UVOT/XRT archival data taken between 2005 and 2017. In the γ -ray band, the peak flux above 100 MeV, F$_{γ}$ = (6 23 ± 0 56) ∙ 10$^{-7}$ photon cm$^{-2}$ s$^{-1}$ observed on MJD 57874 within one week, corresponds to L$_{γ}$ = 2 46 ∙ 10$^{49}$ erg s$^{-1}$ isotropic γ -ray luminosity. The Swift XRT data analyses show that the X-ray emission is characterized by a significantly hard photon index, Γ$_{X-ray}$ ≤ 1.3 , and an X-ray flux of 4 ∙ 10$^{-12}$ erg cm$^{-2}$ s$^{-1}$, which is almost constant over twelve years. The spectral energy distribution is modeled within one-zone leptonic models assuming the emission region is within the broad-line region. The observed X-ray and γ -ray data are modeled as inverse Compton scattering of (i) only synchrotron photons and (ii) synchrotron and external photons on the electron population that produces the radioto-optical emission. The modeling shows that the nonthermal electrons in the jet of PKS 0537-286 have a hard power-law index (<1.9) and that the jet should be particle dominated with a luminosity within 10$^{45}$-10$^{46}$ erg s$^{-1}$.