2013/07/02 by B. Rani, B. Lott, T. P. Krichbaum +2 · 1 citation
Physics and Astronomy · #astro-ph.CO #astro-ph.HE
paper · pdf · doi:10.1051/0004-6361/201321440
11 pages, 8 figures, accepted for publication in A&A
arxiv created 2013/07/02 · arxiv updated 2015/06/16
We present a γ-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 γ-ray flares allow us to constrain the location and size of the γ-ray emission region in the source. The γγ-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 γ-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 γ-ray spectral breaks. Our study suggests that the γ-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.