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Fermi-LAT Detection of a Hard Spectrum and Enhanced Gamma-ray Emission from the Blazar PMN J2052-5533

ATel #8096; Bryce Carpenter (CUA/NASA/GSFC), Jeff Magill (UMCP/NASA/GSFC) and Roopesh Ojha (NASA/GSFC/UMBC) on behalf of the Fermi Large Area Telescope Collaboration
on 25 Sep 2015; 15:13 UT
Credential Certification: Roopesh Ojha (Roopesh.Ojha@gmail.com)

Subjects: Gamma Ray, >GeV, AGN, Blazar, Quasar

Referred to by ATel #: 8114, 8282

The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope has observed an unusually hard spectrum gamma-ray flare from a source positionally consistent with the blazar PMN J2052-5533 (3FGL J2051.8-5535; Acero et al. 2015, ApJS 218, 23), with coordinates RA: 20h52m13.68s, Dec: -55d33m10.0s, J2000, (Healey et al. 2007, ApJS, 171, 61). There is no redshift reported for this source in the literature.

Preliminary analysis indicates that on 23 September 2015 this source was in a high-flux state, with a daily averaged gamma-ray flux (E>100MeV) of (0.3+/-0.1) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only) corresponding to a flux increase of a factor of about 16 with respect to the four-year average flux of 3FGL J2051.8-5535. The corresponding photon spectral index (E>100MeV) of 1.6+/-0.2 is considerably harder than the average index of 2.5+/-0.2 for the 3FGL source.

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. We encourage further multifrequency observations of this source. For this source the Fermi LAT contact person is Bryce Carpenter (carpb01@gmail.com).

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.