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Fermi LAT detection of a GeV flare from blazar B2 1520+31

ATEL # 2026; S. Cutini (ASDC) and E. Hays (NASA/GSFC) on behalf of Fermi LAT collaboration
on 21 Apr 2009; 22:45 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: Elizabeth Hays (

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

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 B2 1520+31 (RA: 15 22 09.99 , Dec: +31 44 14.4 , J2000, A. J. Beasley et al. 2002, ApJS, 41, 13) since April 20, 2009.

This object is a known Flat Spectrum Radio Quasar with a redshift of 1.487 (D. Sowards-Emmerd et al. 2005, ApJ, 626, 95).

Preliminary analysis indicates that on April 20, 2009, the source was in a high state with a gamma-ray flux (E>100MeV) of 1.0 +/-0.3 e-6 ph/cm^2/s (statistical only) on a daily time scale and reached a value of 1.9 +/- 0.7 e-6 ph/cm^2/s (statistical only) in the 6-hour interval starting at 06:00 UT of the same day. During this period the source has a flux around 4 times greater than the average flux reported in the three month LAT Bright AGN Source List (A. Abdo et al. 2009,

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 Dario Gasparrini (

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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