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Fermi LAT detection of a GeV flare from blazar PMN J2345-1555

ATEL # 2408; S. Ciprini (Perugia Univ. / ASI-INAF, Italy), on behalf of the Fermi Large Area Telescope Collaboration
on 28 Jan 2010; 22:34 UT
Password Certification: Stefano Ciprini (

Subjects: Gamma Ray, >GeV, AGN, Quasars

The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed an increasing gamma-ray flaring activity from a source positionally consistent with  the flat spectrum radio quasar  PMN J2345-1555 (also know as IVS B2342-161 and 1FGL J2344.6-1554,  VLBI coordinates, J2000, R.A.: 23h45m12.4623s,  Dec.: -15d55m07.834s, Petrov et al. 2006, AJ, 131, 1872). The redshift of this source is 0.621 (Healey et al. 2008, ApJS, 175, 97), its parsec-scale radio structure is dominated by a compact core (see MOJAVE database, Lister et al., 2009, AJ, 137, 3718), which is typical for a faint blazar.

Preliminary analysis indicates that the source on 2010, January 27 was in a high state with an averaged daily gamma-ray flux (E>100MeV) of (1.0 +/- 0.2) x 10^-6 (statistical only) photons cm^-2 s^-1, representing a factor of about 25 times the averaged flux reported in the first year catalog, and a photon index 2.0 +/- 0.1. This blazar is showing increased gamma-ray activity from January  20. 

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 encourage multiwavelength observations. For this source the Fermi LAT contact person is S. Ciprini (

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.

 MOJAVE page of the source.

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R. E. Rutledge , Editor
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