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Constraining the location of rapid gamma-ray flares in the FSRQ 3C 273

B. Rani B. Lott 1 T. P. Krichbaum L. Fuhrmann J. A. Zensus
CENBG - Centre d'Etudes Nucléaires de Bordeaux Gradignan
Abstract : We present a \gamma-ray photon flux and spectral variability study of the flat-spectrum radio quasar 3C 273 over a rapid flaring activity period between September 2009 to April 2010. Five major flares are observed in the source during this period. The most rapid flare observed in the source has a flux doubling time of 1.1 hr. The rapid \gamma-ray flares allow us to constrain the location and size of the \gamma-ray emission region in the source. The \gamma \gamma-opacity constrains the Doppler factor, δγ≥ 10 for the highest energy (15 GeV) photon observed by the {\it Fermi}-Large Area Telescope (LAT). Causality arguments constrain the size of the emission region to 1.6×1015 cm. The \gamma-ray spectra measured over this period show clear deviations from a simple power law with a break in 1-2 GeV energy range. We discuss possible explanations for the origin of the \gamma-ray spectral breaks. Our study suggests that the \gamma-ray emission region in 3C 273 is located within the broad line region (<1.6 pc). The spectral behavior and temporal characteristics of the individual flares indicate the presence of multiple shock scenarios at the base of the jet.
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Submitted on : Monday, December 9, 2013 - 9:54:36 AM
Last modification on : Monday, November 16, 2020 - 4:10:11 PM

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B. Rani, B. Lott, T. P. Krichbaum, L. Fuhrmann, J. A. Zensus. Constraining the location of rapid gamma-ray flares in the FSRQ 3C 273. Astronomy and Astrophysics - A&A, EDP Sciences, 2013, 557, pp.A71. ⟨10.1051/0004-6361/201321440⟩. ⟨in2p3-00915615⟩



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