Fermi-Large Area Telescope observations of the brightest Gamma-ray flare ever detected from CTA 102

TL;DR

This study reports the detection of the brightest gamma-ray flare from CTA 102, analyzing its temporal and spectral properties, and modeling the emission with a single-region leptonic approach across multiple wavelengths.

Contribution

First detailed multi-wavelength analysis and modeling of the brightest gamma-ray flare from CTA 102, revealing significant electron luminosity increase during flares.

Findings

Highest gamma-ray flux ever from CTA 102.

Significant increase in electron luminosity during flares.

Single emission region explains spectral energy distributions.

Abstract

We present a multi-wavelength 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 Sep, 2016 to Mar, 2017. In the 190 days of 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 $\gamma$-ray flux of (30.12$\pm$4.48)$\times 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 modelling of the pre-flare, rising state, flares and decaying state has been done. A single emission region of size $6.5\times 10^{16}$ cm has been used in our work to explain the multi-wavelength spectral energy distributions. During flares the luminosity in electrons increases nearly seventy times compared to the pre-flare state.