Published in

American Astronomical Society, Astrophysical Journal Letters, 1(714), p. L73-L78, 2010

DOI: 10.1088/2041-8205/714/1/l73

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Fermi Large Area Telescope observations of the exceptional gamma-ray outbursts of 3C 273 in 2009 september

Journal article published in 2010 by Markus Ackermann ORCID, A. A. Abdo, Marco Ajello, Luca Baldini ORCID, J. Ballet, R. D. Blandford, Guido Barbiellini, D. Bastieri ORCID, K. Bechtol, E. D. Bloom, R. Bellazzini, B. Berenji, R. D. Blandford, A. W. Borgland, E. D. Bloom and other authors.
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Data provided by SHERPA/RoMEO

Abstract

We present the light curves and spectral data of two exceptionally luminous gamma-ray outbursts observed by the Large Area Telescope experiment on board the Fermi Gamma-ray Space Telescope from 3C 273 in 2009 September. During these flares, having a duration of a few days, the source reached its highest gamma-ray flux ever measured. This allowed us to study, in some details, their spectral and temporal structures. The rise and the decay are asymmetric on timescales of 6 hr, and the spectral index was significantly harder during the flares than during the preceding 11 months. We also found that short, very intense flares put out the same time-integrated energy as long, less intense flares like that observed in 2009 August.