Long term multi-wavelength analysis of the Flat Spectrum Radio Quasar OP 313

Abstract

The Flat Spectrum Radio Quasar OP 313 is a high-redshift blazar that was characterized by intense γ-ray emission starting from November 2023 to March 2024, as observed by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi). We present a multi-wavelength analysis covering 15 years of Fermi-LAT observations, from August 2008 to March 2024, to understand the mechanisms involved in particle acceleration inside the jet of this galaxy, and how emitted radiation in different wavelengths is connected. We analyzed a large sample of datasets coming from different facilities and projects to look at the trend in the multi-wavelength light-curves. From these, we identified the 7 most intense γ-ray flaring periods, and we analyzed each of them to unveil the responsible physical mechanisms. We realized for each of them the photon index versus flux plot in order to identify potential hysteresis patterns, and then, a kinematic study of the VLBA dataset was pursued to see if new knots arose in the jet before or during the 7 flaring periods we see. Finally, we performed an SED modeling for 2 of the 7 flaring periods. From the SED modeling, we found that a photon field coming from the dusty torus outside the jet is responsible for the γ-ray emission we saw starting from November 2023.