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Fermi LAT detection of increasing gamma-ray activity of blazar OJ 287

ATel #3680; L. Escande (CENBG) & F. K. Schinzel (MPIfR), on behalf of the Fermi Large Area Telescope Collaboration
on 12 Oct 2011; 07:46 UT
Credential Certification: Kirill Sokolovsky (kirx@scan.sai.msu.ru)

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

Referred to by ATel #: 3681, 3682

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 optically bright BL Lac object OJ 287 (RA: 08h 54m 48.874s , Dec: +20d 06m 30.64s, J2000.0, Johnston et al. 1995, AJ, 110, 880) at z=0.306 (Falomo, Scarpa, & Bersanelli 1994, ApJS, 93, 125; Sitko & Junkkarinen 1985, PASP, 97, 1158).

Preliminary analysis indicates that the source on 10 October 2011 was in a high state with a gamma-ray flux (E>100MeV) of (1.0+/-0.2) x 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This flux is equivalent to the one reported by Ciprini et al. in ATel #2256, in October 2009. This flux represents an increase by a factor of about 16 with respect to the average flux for the first two years of the Fermi mission, as listed in the 2FGL catalog (2FGL J0854.8+2005; Abdo et al. 2011, submitted to ApJS, arXiv:1108.1435). The peak flux of (2.0+/-0.6) x 10^-6 photons cm^-2 s^-1 on a 6h time scale was reached between 06:00 and 12:00 UT on 10 October 2011. The source has been detected sporadically in the last few days.

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 S. Ciprini (stefano.ciprini@pg.infn.it), E. Ferrara (Elizabeth.C.Ferrara@nasa.gov), and K. Sokolovsky (kirx@scan.sai.msu.ru).

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.