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Fermi-LAT detection of a GeV flare from a source positionally consistent with PKS 1244-255

ATEL # 1894; A. Tramacere (CIFS Torino/SLAC Stanford), N. Rea (University of Amsterdam/IEEC-CSIC), on behalf of the Fermi Large Area Telescope Collaboration
on 8 Jan 2009; 14:49 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: Nanda Rea (N.Rea@sron.nl)

Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Black Holes, Transients

The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope (formerly GLAST, launched on June 11, 2008), has observed a large flare from a GeV source positionally consistent with PKS 1244-255, at: RA = 191.6 and Dec = -25.7 (error circle at 95% = 0.2 deg).

PKS 1244-255, with a redshift z~0.64 is also reported in the three-year WMAP point source catalog (G. Hinshaw et al., 2007, ApJS 170). The low energy bump of the Spectral Energy Distribution (SED) of PKS 1244-255 reported in the ASI/ASDC Multi-frequency Catalogue of Blazars (Massaro et. al 2008, arXiv:0810.2206; http://www.asdc.asi.it/bzcat/) peaks around 10^12 Hz.

Preliminary analysis of the Fermi-LAT data indicates that during January 4, 2009, the source was detected with a flux (E >100 MeV) of 0.4+/-0.2 x 10^-6 ph cm^-2 s^-1, rising in January 5, 2009, to 0.8+/-0.2 x 10^-6 ph cm^-2 s^-1 on a daily time scale, and reaching a value of 1.9+/-0.5 x 10^-6 ph cm^-2 s^-1 on a six-hour time scale starting from 18:00:00 (UT) of the same day. On January 7, 2009 the source was detected with a flux (E >100 MeV) of 0.4+/-0.2 x 10^-6 ph cm^-2 s^-1. The flux in the past few days is more than one order of magnitude brighter than the Fermi-LAT detection of the past months.

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. In consideration of the violent outburst we strongly encourage multiwavelength observations in particular the evolution of the flux in the optical, IR and mm band to follow the evolution of the peak energy and peak flux of the low energy bump.

For this source the Fermi-LAT contact persons are Andrea Tramacere (tramacer@slac.stanford.edu) and Nanda Rea (N.Rea@uva.nl) 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.


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