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Fermi LAT detection of a GeV flare from the high redshift blazar B3 1343+451

ATEL # 2217; Rolf Buehler (SLAC) on behalf of the Fermi Large Area Telescope Collaboration
on 26 Sep 2009; 21:05 UT
Password Certification: Rolf Buehler (

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

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 the FSRQ B3 1343+451 (z=2.534, Shaw, M.S. et al., in preparation; J2000, RA: 13h45m33.2s, Dec: +44d53'00", Kovalev, Y. Y. et al., 2007, AJ 133, 1236). Preliminary analysis indicates that the source is in a high state. The source has been detected daily, with an average >100 MeV flux of (0.83+/-0.12) x 10-6 ph s-1 cm-1 between the 22nd and the 25th of September (statistical errors only). This corresponds to a flux increase of a factor of ~15 compared to the average flux measured from this source over the last year. The highest daily-averaged flux in this period was measured on the 25th of September, at (1.02+/-0.28) x 10-6 ph s-1 cm-1.

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 is: Rolf Buehler (

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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