Fermi LAT detection of increased gamma-ray activity from blazar S5 0716+71
A. Cannon (University College Dublin, GSFC) on behalf of the Fermi Large Area Telescope Collaboration
The Large Area Telescope (LAT), one of two instruments on-board the Fermi Gamma-ray Space Telescope, has observed an increase in gamma-ray activity from a source positionally coincident with the Low-frequency BL Lac object S5 0716+71 (also known as 1FGL J0721.9+7120, Abdo et al. 2010, ApS, 188, 405; R.A.= 07h21m53.4484s, Dec.=+71d20m36.363s, J2000, Johnston et al. 1995, AJ 110, 880). Nilsson et al. (2008, A&A 487, L29) derived a photometric redshift for this source of z = 0.31+/- 0.08.

Preliminary analysis indicates that the source on July 12th, 2011, was detected in a high state with an average daily flux (E>100 MeV) of (1.4+/-0.3)x10^-6 ph cm^-2 s^-1 (statistical uncertainty only), peaking with a flux (E>100 MeV) of (2.6+/-0.7)x10^-6 ph cm^-2 s^-1 in the 6-hour interval starting at 12:00 UT of the same day. The source continued to be bright on July 13th, 2011, with a similar average daily flux (E>100 MeV) of (1.4+/-0.2) x10^-6 ph cm^-2 s^-1. This represents a greater than one order of magnitude increase in flux with respect to the average flux reported in the first Fermi LAT catalog (Abdo et al. 2010, ApS, 188, 405) and is the first flare from this source reported by Fermi. The source was also observed on July 9th and 10th, 2011, with average daily fluxes of (0.7+/-0.2) x10^-6 ph cm^-2 s^-1 and (0.9+/-0.2) x10^-6 ph cm^-2 s^-1, respectively.

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. In consideration of the activity of this source we strongly encourage multiwavelength observations. The Fermi LAT contact person for this source is D. Bastieri (bastieri@pd.infn.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.
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