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Fermi LAT detection of renewed GeV activity from blazar 3C 279

ATel #6036; Stefano Ciprini (ASI ASDC & INAF Rome), Josefa Becerra Gonzalez (NASA GSFC) on behalf of the Fermi Large Area Telescope Collaboration
on 1 Apr 2014; 17:19 UT
Credential Certification: Stefano Ciprini (stefano.ciprini@asdc.asi.it)

Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar, Quasar

Referred to by ATel #: 6053, 7633

The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed high-level gamma-ray activity from a source positionally consistent with the blazar 3C 279 (RA: 194.046527 deg, Dec: -5.789312 deg, J2000; Johnston et al.1995, AJ, 110, 880). This source is classified as a flat spectrum radio quasar (FSRQ) at redshift of 0.536 (Marziani et al. ApJS, 1996, 104, 37) and is one of the three FSRQs known to be VHE gamma-ray emitters.

Preliminary analysis indicates that on 2014 March 30 the daily averaged flux (E>100MeV) was (4.0 +/- 0.5) x 10^-6 photons cm^-2 s^-1, more than a factor of 6 greater than reported in the second Fermi LAT catalog (2FGL J1256.1-0547, Nolan et al. 2012, ApJS 199, 31). The corresponding average gamma-ray spectrum had a photon index of about 2.1. The flux of 3C 279 peaked at (1.0 +/- 0.2) x 10^-5 photons cm^-2 s^-1 in a 6-hour interval on the same day (errors are statistical only).

This outburst corresponds to the second highest gamma-ray flux ever observed by the LAT from this blazar since the start of the Fermi mission, after the flaring activity reported last December 2013 in ATel#5680. At 21:56:26 UT on March 31, Fermi started a 350ks target of opportunity observation to increase LAT exposure on 3C 279.

The Fermi LAT contact people for this source are Greg Madejski (madejski@slac.stanford.edu) and Masaaki Hayashida (mahaya@slac.stanford.edu). In consideration of the ongoing activity of this source we strongly encourage multiwavelength observations.

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.