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Fermi LAT detection of a GeV flare from blazar PKS 1622-253

ATEL # 2231; Luis C. Reyes (U. of Chicago - KICP) on behalf of the Fermi LAT Collaboration
on 6 Oct 2009; 15:07 UT
Password Certification: Luis C. Reyes (

Subjects: Gamma Ray, >GeV, Transients

The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed an increasing gamma-ray flux from a source positionally consistent with PKS 1622-253 (RA: 16h25m46.9s, Dec: -25d27'38", J2000). Preliminary analysis indicates that the source on Oct 4 was in a high state with a gamma-ray flux (E>100MeV) of (1.9 +/- 0.2) x 10-6 ph cm-2 s-1. This corresponds to a relative increase up to a factor of ~17 with respect to the average flux of PKS 1622-253 during the first year of Fermi operation. This blazar at z=0.786 (di Serego Alighieri, S. et al. 1994, MNRAS, 269, 998) was detected by EGRET as 3EG J1626-2519 (Hartman, R.C. et al. 1999, ApJS, 123, 79).

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. In consideration of the ongoing activity of this source we strongly encourage multiwavelength observations. For this source the Fermi LAT contact person is Luis C. Reyes (

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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