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Fermi LAT detection of a GeV flare from blazar B2 2319+31

ATel #5231; D. Gasparrini (ASDC/INAF) and C. C. Cheung (NRL) on behalf of the Fermi LAT collaboration
on 28 Jul 2013; 07:05 UT
Credential Certification: Dario Gasparrini (dario.gasparrini@asdc.asi.it)

Subjects: Gamma Ray, >GeV, AGN, Blazar

The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, observed a gamma-ray outburst from a source positionally consistent with the flat spectrum radio quasar B2 2319+31, also known as TXS 2319+317 and BZQJ2321+3204 (RA: 23h21m54.9559s DEC :+32d04m07.622s, J2000.0, Petrov et al. 2005) with redshift z=1.489 (Shaw et al. 2012).

Preliminary analysis indicates that on 2013 July 26, B2 2319+31 appeared in a flaring state with a daily gamma-ray flux (E>100MeV) of 0.7+/-0.2 x 10^-6 photons cm^-2 s^-1 (statistical uncertainty only), about 27 times the average flux of 2FGL J2322.2+3206, the gamma-ray counterpart (Nolan et al. 2012, ApJS 199, 31). The source was already active on July 14, when it reached a similar daily gamma-ray flux (E>100MeV) of 0.8+/-0.2 x 10^-6 photons cm^-2 s^-1 (statistical uncertainty only) in coincidence with the historically brightest optical state reported by MASTER in Atel #5218.

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. In consideration of the ongoing prominent gamma-ray outburst, we strongly encourage multiwavelength observations of this object. For this source the Fermi LAT contact person is D. Gasparrini (gasparrini@asdc.asi.it).

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.