Fermi LAT detection of a GeV flare from quasar 4C +38.41
ATel #3333; A. Szostek (Stanford/SLAC), on behalf of the Fermi Large Area Telescope Collaboration
on 9 May 2011; 22:19 UT
Credential Certification: Anna Szostek (aszostek@slac.stanford.edu)
Subjects: Gamma Ray, >GeV, AGN, Transient
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 coincident with 4C +38.41 (RA: 16h 35m 15.493s, Dec. +38d 08m 04.50s (J2000); Johnston et al. 1995, AJ, 110, 880). This is a flat spectrum radio quasar also known as B2 1633+38, OS 356 and 3EG J1635+3813, with a redshift of 1.814 (Adelman-McCarthy et al. 2008, ApJS, 175, 297).
Preliminary analysis indicates that the source on May 8, 2011 was in a high state with a gamma-ray flux (E>100 MeV) of (2.1 +/- 0.3) x 10^-6 photons/cm^2/s (statistical uncertainty only). During May 7-8, 2011, the flux has increased by a factor of 10 over the average flux reported in the first Fermi-LAT catalog (1FGL 1635.0+3808, Abdo et al. 2010, ApJS, 188, 405). The flux is also higher than during a GeV flare reported on February 23, 2010 (ATel #2456).
Since Fermi operates in an all-sky scanning mode, regular monitoring of this source will continue. In consideration of the ongoing activity of this source we strongly encourage multiwavelength observations. The Fermi LAT contact persons are S. Ciprini (stefano.ciprini@pg.infn.it) and S. Buson (buson@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.