Volume 635, March 2020
|Number of page(s)||10|
|Published online||02 March 2020|
Investigation of the γ-ray spectrum of CTA 102 during the exceptional flaring state in 2016–2017
ICRANet-Armenia, Marshall Baghramian Avenue 24a, Yerevan, 0019, Armenia
2 ICRANet, P.zza della Repubblica 10, 65122 Pescara, Italy
Accepted: 27 November 2019
The flat spectrum radio quasar CTA 102 entered an extended period of activity from 2016 to 2017 during which several strong γ-ray flares were observed. By using Fermi large area telescope data, a detailed investigation of γ-ray spectra of CTA 102 during the flaring period was performed. In several periods, the γ-ray spectrum is not consistent with a simple power-law, having a hard photon index with an index of ∼(1.8−2.0) that shows a spectral cut-off around an observed photon energy of ∼(9−16) GeV. The internal γ-ray absorption via photon-photon pair production on the broad-line-region-reflected photons cannot account for the observed cut-off and break even if the emitting region is very close to the central source. This cut-off and break are likely due to a similar intrinsic break in the energy distribution of emitting particles. The origin of the spectral break is investigated through the multiwavelength modeling of the spectral energy distribution in considering a different location for the emitting region. The observed X-ray and γ-ray data is modeled as inverse Compton scattering of synchrotron and/or external photons on the electron population that produces the radio-to-optical emission, which allowed to constrain the power-law index and cut-off energy in the electron energy distribution. The obtained results are discussed in the context of a diffusive acceleration of electrons in the CTA 102 jet.
Key words: quasars: individual: CTA 102 / radiation mechanisms: non-thermal / gamma-rays: galaxies / galaxies: jets
© ESO 2020
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