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Fermi LAT confirmation of a strong GeV flare from 4C 21.35 (PKS 1222+21)

ATel #2349; S. Ciprini (Perugia Univ. / ASI-INAF, Italy), on behalf of the Fermi Large Area Telescope Collaboration
on 16 Dec 2009; 20:35 UT
Credential Certification: Stefano Ciprini (stefano.ciprini@pg.infn.it)

Subjects: Gamma Ray, >GeV, AGN, Quasar

Referred to by ATel #: 2584, 2641, 2686, 2687, 6207

The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed an increasing gamma-ray flaring activity from a source positionally consistent with 4C 21.35 (also known as PKS 1222+21, z=0.432, RA: 12h24m54.4s, Dec: +21d22m46s, J2000). Preliminary analysis indicates that the source on December 15 2009 was in a high state with a gamma-ray flux (E>100MeV) of (3.4 +/- 0.5) x 10^-6 (statistical only) photons cm^-2 s^-1, which represents an increase of a factor of about 40 with respect to the averaged flux level in the past 11 months.

The start of the current phase of bright gamma-ray flaring activity in 4C 21.35 was observed by AGILE (ATEL#2348). Fermi announced in April (ATEL #2021) already a period of increased brightness but at a substantial lower level. 

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. The blazar 4C 21.35 is a "LAT Monitored Source" and, consequently, a quick look estimation of the daily gamma-ray flux observed by Fermi LAT is publicly available. In consideration of the ongoing activity of this source we encourage multiwavelength observations. For this source the Fermi LAT contact persons are G. Iafrate (iafrate@oats.inaf.it) and Y. Tanaka (tanaka@astro.isas.jaxa.jp).

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.