Fermi LAT Detection of a Hard Spectrum Gamma-ray Flare from Gravitationally Lensed Blazar S3 0218+357
ATel #6316; S. Buson (INFN & Univ. of Padova), C. C. Cheung (NRL), on behalf of the Fermi LAT Collaboration
on 16 Jul 2014; 11:02 UT
Credential Certification: Sara Buson (buson@pd.infn.it)
Subjects: Gamma Ray, >GeV, TeV, VHE, Request for Observations, AGN, Blazar
Referred to by ATel #: 6349
The Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope has observed a gamma-ray flare from the gravitationally lensed blazar S3 0218+357 (lens B0218+357) with an unusually hard spectrum. Preliminary analysis indicates that on 2014 July 13 and 14, the gamma-ray source was observed with respective daily averaged fluxes (E>100MeV) of (6.5+/-1.4) x 10^-7 photons cm^-2 s^-1 with hard photon index of 1.4 +/- 0.1 and (6.7+/-1.5) x 10^-7 photons cm^-2 s^-1 with photon index of 1.6 +/- 0.1 (errors are statistical only).
The source, located at a redshift z=0.944+/-0.002 (Cohen et al. 2003, ApJ, 583, 67), was already observed in gamma-ray flaring state in 2012 (ATel #4343, ATel #4371). During past flares observed with the LAT, the spectral hardness did not change from the quiescent state index of 2.3. The gravitationally lensed delayed emission from past flares was also detected 11.46 +/- 0.16 days later (1 sigma; see Cheung et al. 2014, ApJ, 782, L14).
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 (link:http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/source/S3_0218p35).
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 persons are Sara Buson (buson@pd.infn.it) and Teddy Cheung (Teddy.Cheung@nrl.navy.mil).
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.
