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Fermi/LAT detection of strong activity on short timescales of the blazar AO 0235+164

ATel #1784; Luigi Foschini (INAF/IASF-Bologna), Francesco Longo (INFN Trieste), Giulia Iafrate (INAF/OA Trieste) on behalf of the Fermi Large Area Telescope Collaboration
on 15 Oct 2008; 22:16 UT
Credential Certification: Luigi Foschini (foschini@bo.iasf.cnr.it)

Subjects: Gamma Ray, >GeV, AGN, Quasar

Referred to by ATel #: 1785, 1849, 7975, 8802

The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope (formerly GLAST) (launched June 11, 2008) has detected a strong and short increase of gamma-rays from a sky position consistent with the blazar AO 0235+164 (RA = 39.66 deg; Dec = +16.62 deg; z=0.94). The flare occurred on Oct. 14, 2008 and the preliminary flux measurement was (5+/-2)E-6 ph/cm^2/s with 30% systematic uncertainty in a 6 hour period (12-18 UTC), which significantly exceeds the the public announcement flux threshold of 2E-6 ph/cm^2/s (E>100 MeV). The source was already active at the end of September (Corbel and Reyes, ATEL # 1744).

This source is one of the "LAT Monitored Sources" (http://fermi.gsfc.nasa.gov/ssc/data/policy/LAT_Monitored_Sources.html) and consequently, a preliminary estimate of the gamma-ray flux observed by Fermi LAT will be publicly available (http://fermi.gsfc.nasa.gov/ssc/data/access/) after the next weekly data delivery to the Fermi Science Support Center. Please note that these data are produced for daily and weekly integrations, so will not show the high flux reported here from a 6 hour integration.

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 strongly encourage multiwavelength observations. The Fermi LAT contact person for this source is Luis C. Reyes (lreyes@kicp.uchicago.edu).

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.