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Fermi LAT detection of a GeV flare from CGRaBS J1848+3219

ATel #2954; D. Donato (NASA/GSFC), S. Ciprini (Perugia Univ. / ASI-INAF, Italy), C. C. Cheung (NRC, resident at NRL), on behalf of the Fermi LAT Collaboration
on 19 Oct 2010; 18:03 UT
Credential Certification: Davide Donato (davide.donato-1@nasa.gov)

Subjects: Gamma Ray, >GeV, Blazar, Transient

Referred to by ATel #: 2963

The Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope, has observed a gamma-ray flare from a source positionally consistent with the flat spectrum radio quasar CGRaBS J1848+3219, also known as B2 1846+32A (RA = 08:48:22.09, Dec =+32:19:02.6, J2000; A. Beasley et al. 2002 ApJS 141, 13). The source is located at intermediate redshift (z=0.798; D. Sowards-Emmerd et al. 2005 ApJ 626, 95).

Preliminary analysis indicates that the source on October 18, 2010 showed a bright gamma-ray outburst with a daily flux (E>100MeV) of (2.2 +/- 0.3) x10^-6 ph cm^-2 s^-1 (errors are statistical only), a factor of 20 greater than reported in the Fermi-LAT 1st year catalog (1FGL J1848.5+3224; Abdo et al. 2010, ApJS 188, 405). The gamma-ray source was also detected on October 17th with a daily flux (E>100 MeV) of (0.7 +/- 0.2) x10^-6 ph cm^-2 s^-1. This initial flare is coincident with activity observed in the near-infrared (ATel #2953). The source also showed high gamma-ray flux level on daily intervals on September 20 and 22, 2010 (http://fermisky.blogspot.com/).

Because Fermi operates in all-sky survey mode, gamma-ray monitoring of this source will continue. In consideration of the activity of this source we strongly encourage multiwavelength observations. The Fermi LAT contact person for this source is D. Donato (donato@milkyway.gsfc.nasa.gov) .

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.