Fermi-Large Area Telescope Observations of the Brightest Gamma-Ray Flare Ever Detected from CTA 102

Abstract

We present a multiwavelength study of the FSRQ CTA 102 using Fermi-LAT and simultaneous Swift-XRT/UVOT observations. The Fermi-LAT telescope detected one of the brightest flares from this object during 2016 September to 2017 March. In the 190 days of the observation period, the source underwent four major flares. A detailed analysis of the temporal and spectral properties of these flares indicates the flare at MJD 57751.594 has a γ-ray flux of (30.12 ± 4.48) × 10−6 ph cm−2 s−1 (from 90 minutes binning) in the energy range of 0.1–300 GeV. This has been found to be the highest flux ever detected from CTA 102. Time dependent leptonic modeling of the preflare, rising state, flares and decaying state has been done. A single emission region of size 6.5 × 1016 cm has been used in our work to explain the multiwavelength spectral energy distributions. During flares, the luminosity in electrons increases nearly seventy times compared to the preflare state.