Details

Autor(en) / Beteiligte

• Ackermann, M
• Ajello, M
• Bechtol, K
• Berenji, B
• Blandford, R D
• Borgland, A W
• Buehler, R
• Cameron, R A
• Baldini, L
• Bellazzini, R
• Bregeon, J
• Ballet, J
• Barbiellini, G
• Bastieri, D
• Buson, S
• Bonamente, E
• Brigida, M
• Bruel, P
• Burnett, T H
• Caliandro, G. A.

Titel

FERMI GAMMA-RAY SPACE TELESCOPE OBSERVATIONS OF GAMMA-RAY OUTBURSTS FROM 3C 454.3 IN 2009 DECEMBER AND 2010 APRIL

Ist Teil von

• The Astrophysical journal, 2010-10, Vol.721 (2)

Ort / Verlag

United States

Erscheinungsjahr

2010

Quelle

EZB Free E-Journals

Beschreibungen/Notizen

• The flat spectrum radio quasar 3C 454.3 underwent an extraordinary outburst in 2009 December when it became the brightest {gamma}-ray source in the sky for over 1 week. Its daily flux measured with the Fermi-Large Area Telescope at photon energies E>100 MeV reached F{sub 100} = 22 {+-} 1 x 10{sup -6} photon cm{sup -2} s{sup -1}, representing the highest daily flux of any blazar ever recorded in high-energy {gamma}-rays. It again became the brightest source in the sky in 2010 April, triggering a pointed-mode observation by Fermi. The correlated {gamma}-ray temporal and spectral properties during these exceptional events are presented and discussed. The main results show flux variability over time scales less than 3 hr and very mild spectral variability with an indication of gradual hardening preceding major flares. The light curves during periods of enhanced activity in 2008 July-August and 2010 December show strong resemblance, with a flux plateau of a few days preceding the major flare. No consistent loop pattern emerged in the {gamma}-ray spectral index versus the flux plane as would be expected in acceleration and cooling scenarios. The maximum energy of a photon from 3C 454.3 is {approx}20 GeV and a minimum Doppler factor of {approx}13 is derived. The {gamma}-ray spectrum of 3C 454.3 shows a significant spectral break between {approx}2 and 3 GeV that is very weakly dependent on the flux state, even when the flux changes by an order of magnitude.