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Fermi LAT detection of a GeV flare from 3C 273

ATel #2168; D. Bastieri (INFN/University Padova) on behalf of the Fermi Large Area Telescope Collaboration
on 20 Aug 2009; 20:36 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Denis Bastieri (denis.bastieri@pd.infn.it)

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

Referred to by ATel #: 2200, 2330

The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed an increasing gamma-ray flux from a source positionally consistent with 3C 273 (J2000, R.A.: 12:29:06.6997, Dec: +02:03:08.598 Johnston et al. 1995, AJ, 110, 880). Preliminary analysis indicates that the source on August 19th, 2009, has brightened to a high state with an average gamma-ray flux over the day (E>100MeV) of 3.18 ± 0.54 (statistical only) × 10−6 ph cm−2 s−1 and peaking at 5.48 ± 1.85 (statistical only) × 10−6 ph cm−2 s−1 in the 6 hour period between 0 and 6 UT of August 20th. This is the second time that Fermi has reported a similar GeV flare for this blazar (ATel #1707, 8 Sept 2008). 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. For this source the Fermi LAT contact persons are Jim Chiang (jchiang@slac.stanford.edu) and Werner Collmar (wec@mpe.mpg.de). 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.