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Fermi LAT detection of Increased Flux from new gamma-ray blazar PKS 0250-225

ATEL # 1933; Stephane Corbel (University Paris Diderot & CEA Saclay) and Luis C. Reyes (KICP - University of Chicago) on behalf of the Fermi Large Area Telescope Collaboration
on 19 Feb 2009; 21:47 UT
Password Certification: Gino Tosti (

Subjects: Gamma Ray, >GeV, Transients

The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope (formerly GLAST, launched June 11, 2008), has observed an increasing gamma-ray flux from a source positionally consistent with PKS 0250-225 (RA: 02h52m47.9s, Dec:-22d19m25s, J2000). Preliminary analysis indicates that PKS 0250-225 (z=1.427 ; as CGRaBS J0252-2219 in Healey S. et al. 2007, ApJS, 175, 97) has been in a high state since Feb 17 with a gamma-ray flux (E>100MeV) of (0.5 +/- 0.1) x 10-6 ph cm-2 s-1, which represents a > 3-fold increase in flux with respect to the average preliminary flux observed during the first 6 months of data of the Fermi mission and about an 8-fold increase with respect to the first 3 months, suggesting thus a long-term trend of increasing flux.

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

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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