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Fermi LAT detection of a GeV flare from PKS B 1622-297

ATEL # 2531; Eric Wallace (University of Washington, Seattle), Frank Schinzel (MPIfR, Bonn); on behalf of the Fermi LAT Collaboration
on 1 Apr 2010; 22:05 UT
Password Certification: Teddy Cheung (

Subjects: Gamma Ray, >GeV, AGN, Quasars

The Large Area Telescope (LAT), on board the Fermi Gamma-Ray Space Telescope, has detected a heightened gamma-ray flux from a source positionally consistent with the blazar PKS B 1622-297 (J2000, RA = 16h26m06.0208s, Dec = -29d51m26.970s, Johnston, et al. 1995 AJ, 110, 880; z=0.815, Wright & Otrupcek 1990, Parkes Catalogue). Preliminary analysis indicates that on March 29, the source was in a high state, with flux (E>100 MeV) of (5.7 +/- 2.4)*10^-7 photons/cm^2/s, about an order of magnitude greater than its average flux over the first 11 months of Fermi operations (The Fermi-LAT Collaboration, arXiv:1002.2280). The average flux over the preceding week (March 23-29) was (3.1 +/- 1.3)*10^-7 photons/cm^2/s. An optical/IR flare of this source was recently reported (Buxton et al., ATel #2522). This blazar produced one of the brightest gamma-ray flares seen by EGRET (Mattox et al. 1997, ApJ 476, 692).

Because Fermi operates in all-sky survey mode, regular gamma-ray monitoring of this source will continue. In consideration of the ongoing activity of this source we strongly encourage multiwavelength observations. The Fermi LAT contact person for this source is Eric Wallace (

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.

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