Fermi observations of gamma-ray outbursts from 3C 454.3 in December 2009 and April 2010

摘要

The flat-spectrum-radio-quasar 3C 454.3 underwent an extraordi-nary outburst in December 2009 when it became the brightest gamma-ray source in the sky for over one week. Its daily flux measured with the Fermi Large Area Telescope at photon energies E > 100 MeV reached 22 ± 1 × 10~(-6) ph cm~(-2)s~(-1). It again became the brightest source in the sky in April 2010, triggering a pointed-mode observation by Fermi. The γ-ray temporal and spectral properties during these exceptional events are presented and discussed.