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Fermi LAT detection of increasing gamma-ray activity of blazar 4C +28.07

ATel #3670; F. K. Schinzel (MPIfR), S. Ciprini (ASI-INAF), on behalf of the Fermi Large Area Telescope Collaboration
on 5 Oct 2011; 16:46 UT
Credential Certification: Frank Schinzel (schinzel@mpifr-bonn.mpg.de)

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

Referred to by ATel #: 3672, 3674, 3676, 3709

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 4C +28.07 (RA: 2h37m52.406s, Dec: +28d48m8.990s, J2000, Fey et al. 2004, AJ, 127, 3587) at z=1.207 (Veron-Cetty & Veron 1998).

Preliminary analysis indicates that the source on 3 October 2011 was in a high state with a gamma-ray flux (E>100MeV) of (1.4 +/-0.3) x 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This is the highest flux value of 4C +28.07 observed by Fermi so far and represents an increase by a factor of about 14 with respect to the average flux level for the first two years of the Fermi mission, as listed in the 2FGL catalog (2FGL J0237.8+2846; Abdo et al. 2011, submitted to ApJS, arXiv:11081435). The flux measured on 6-hour intervals increased continuously on 3 October and reached a flux level of (3.5 +/-1.5) x 10^-6 photons cm^-2 s^-1 (statistical uncertainty only) between 18:00 and 24:00 UT on 3 October 2011.

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. For this source the Fermi LAT contact persons are Frank Schinzel (schinzel@mpifr.de) and Roopesh Ojha (roopesh.ojha@gmail.com).

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.