Clues on High Energy Emission Mechanism from Blazar 3C 454.3 during 2015 August Flare

Abstract

We perform a detailed spectral study of a recent flaring activity from the Flat Spectrum Radio Quasar (FSRQ), 3C\,454.3, observed simultaneously in optical, UV, X-ray and $\gamma$-ray energies during 16 to 28 August, 2015. The source reached its peak $\gamma$-ray flux of $(1.9\pm 0.2)\times 10^{-05}\mathrm{ph}\mathrm{c}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$ on 22 August. The time averaged broadband spectral energy distribution (SED) is obtained for three time periods, namely "flaring state"; covering the peak $\gamma$-ray flux, "post flaring state"; immediately following the peak flare and "quiescent state"; separated from the flaring event and following the post flaring state. The SED corresponding to the flaring state is investigated using different emission models involving synchrotron, synchrotron self Compton (SSC) and external Compton (EC) mechanisms. Our study suggests that the X-ray and $\gamma$-ray emission from 3C\,454.3 cannot be attributed to a single emission mechanism and instead, one needs to consider both SSC and EC mechanisms. Moreover, the target photon energy responsible for the EC process corresponds to an equivalent temperature of 564 K, suggesting that the flare location lies beyond the broad line emitting region of the FSRQ. SED fitting of the other two flux states further supports these inferences.

28 pages, 9 figures, 5 tables Accepted 2017 May 12. Received 2017 May 12; in original form 2016 November 07

References in corpus (5)

• Swift and infra-red observations of the blazar 3C~454.3 during the giant X-ray flare of May 2005
• Multiwavelength observations of 3C 454.3. I. The AGILE 2007 November campaign on the "Crazy Diamond"
• The high activity of 3C 454.3 in autumn 2007. Monitoring by the WEBT during the AGILE detection
• Gamma-ray Flare of PKS 1222+216 in 2010: Effect of Jet Dynamics at the Recollimation Zone
• MAGIC upper limits to the VHE gamma-ray flux of 3C454.3 in high emission state

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