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Fermi LAT detection of an extraordinary GeV outburst from 3C 454.3

ATel #2328; L. Escande (CNRS/IN2P3 Bordeaux) and Y. T. Tanaka (ISAS/JAXA) on behalf of the Fermi Large Area Telescope Collaboration
on 3 Dec 2009; 21:20 UT
Credential Certification: Dario Gasparrini (dario.gasparrini@asdc.asi.it)

Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Quasar

Referred to by ATel #: 2329, 2330, 2332, 2333, 2344, 2345, 2534, 2535, 3041

The Large Area Telescope (LAT) one of the two instruments on the Fermi Gamma-ray Space Telescope, has detected an extraordinary gamma-ray flare from the blazar 3C 454.3 (J2000, RA: 22:53:57.748, Dec: +16:08:53.56, Fey et al. 2004, AJ, 127, 3587). Preliminary analysis indicates that the source on December 2nd, 2009, has reached a very high state with an average gamma-ray flux over the day (E>100MeV) of 22 ± 1 (statistical only) × 10-6 ph cm-2 s-1 and peaking at 26 ± 3 (statistical only) × 10-6 ph cm-2 s-1 in the 6 hour period between 12 and 18 UT of December 2nd. This flare is the highest ever recorded in this energy range and represents more than twice the flux of the Vela pulsar, the brightest persistent source in the gamma-ray sky. This flare has been detected by the AGILE Collaboration with a flux of 18 ± 4 x 10-6 ph cm-2 s-1 (ATel #2326) on December 3rd.

Recent gamma-ray activity exhibited by 3C 454.3 was reported by the AGILE Collaboration (ATel #2322) on December 1st with a flux of 7 x 10-6 ph cm-2 s-1. A correlated brightening in the optical band was reported (Atel #2325) on December 2nd by the GASP Collaboration. The last gamma-ray flare displayed by 3C 454.3 reported by Fermi was on September 15th (ATel #2200) with a gamma-ray flux reaching 6.0 ± 0.6 (statistical only) × 10-6 ph cm-2 s-1.

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. The blazar 3C 454.3 is a "LAT Monitored Source"(link: http://fermi.gsfc.nasa.gov/ssc/data/policy/LAT_Monitored_Sources.html ), and consequently, a quick look estimation of the daily gamma-ray flux observed by Fermi LAT is publicly available(link: http://fermi.gsfc.nasa.gov/ssc/data/access/ ). In consideration of the ongoing activity of this source we strongly encourage multiwavelength observations. The Fermi LAT contact person is Greg Madejski (madejski@stanford.edu).

The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.