Fermi LAT detection of GeV flares from 3C454.3 and 3C273

ATel #2200; A. B. Hill (LAOG); on behalf of the Fermi Large Area Telescope Collaboration
on 17 Sep 2009; 03:08 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Dario Gasparrini (dario.gasparrini@asdc.asi.it)

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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 454.3 (J2000, RA: 22:53:57.748, Dec: +16:08:53.56, Fey et al. 2004, AJ, 127, 3587). Preliminary analysis indicates that the source on September 15th, 2009, has brightened to a high state with an average gamma-ray flux over the day (E>100MeV) of 6.0 ± 0.6 (statistical only) × 10−6 ph cm−2 s−1 and peaking at 7.2 ± 1.2 (statistical only) × 10−6 ph cm−2 s−1 in the 6 hour period between 6 and 12 UT of September 15th. In recent weeks optical, IR and mm flares have been observed from this source (ATEL #2181; ATEL #2155; ATEL #2150). This is the second time that Fermi has reported activity for this blazar (ATEL #1628, 24 July 2008).

The LAT has also observed an increasing gamma-ray flux from a source positionally consistent with 3C 273 (J2000, R.A.: 12:29:06.700, Dec: +02:03:08.60 Johnston et al. 1995, AJ, 110, 880). Preliminary analysis indicates that the source on September 15th, 2009, has brightened to a high state with an average gamma-ray flux over the day (E>100MeV) of 3.1 ± 0.5 (statistical only) × 10−6 ph cm−2 s−1 and peaking at 5.0 ± 1.2 (statistical only) × 10−6 ph cm−2 s−1 in the 6 hour period between 0 and 6 UT of September 15th. This is the third time that Fermi has reported a similar GeV flare for this blazar (ATEL #1707, 8 Sept 2008; ATEL #2168, 19 August 2009).

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. The blazars 3C 454.3 and 3C 273 are "LAT Monitored Sources"(link: http://fermi.gsfc.nasa.gov/ssc/data/policy/LAT_Monitored_Sources.html ), and consequently, a quick look estimation of the daily gamma-ray flux observed by Fermi LAT is publicly available(link: http://fermi.gsfc.nasa.gov/ssc/data/access/ ).

In consideration of the ongoing activity of this source we strongly encourage multiwavelength observations. The Fermi LAT contact persons are: 3C 454.3, Greg Madejski (madejski@stanford.edu); 3C 273, Jim Chiang (jchiang@slac.stanford.edu), 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.