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Fermi LAT Detection of Renewed Activity from B2 2308+34

ATel #5477; S. Buson (INFN/Univ. Padova) on behalf of the Fermi LAT Collaboration
on 16 Oct 2013; 17:14 UT
Credential Certification: Sara Buson (buson@pd.infn.it)

Subjects: Gamma Ray, Request for Observations, AGN, Blazar, Variables

Referred to by ATel #: 5487, 5517, 5564

The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope has observed increasing gamma-ray flux from a source positionally consistent with the Flat Spectrum Radio Quasar B2 2308+34 (R.A.=23:11:05.3288 Dec.=+34:25:10.905, J2000.0; z=1.817, Wills & Wills 1976, ApJS, 31,143).

Preliminary analysis indicates that, on 2013 October 15, B2 2308+34 was detected with a daily averaged flux (E>100MeV) of (1.0 +/- 0.2) x 10^-6 photons/cm^2/s (errors are statistical only) and a daily photon index of 2.0+/-0.1. The observed flux is about 13 times the average flux of its gamma-ray counterpart 2FGL J2311.0+3425 (Nolan et al. 2012, ApJS, 199, 31). This source is also reported in the 1FHL catalog of LAT sources detected above 10 GeV (1FHL J2311.0+3425, Ackermann et al. 2013, ApJS, submitted, arXiv:1306.6772).

A previous detection of B2 2308+34 at a similar gamma-ray flux on 2010 August 8 (ATel #2783) signaled the beginning of an active phase that lasted for a few months. This is the first LAT detection of this source on daily timescales since mid-2011. This source is one of the "LAT Monitored Sources" and consequently a preliminary estimation of the daily gamma-ray flux observed by Fermi LAT is publicly available at http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/source/B2_2308p34

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 multi-wavelength observations. For this source the Fermi LAT contact person is Filippo D'Ammando (dammando@ira.inaf.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.