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Fermi LAT detection of a GeV flare from the high-redshift blazar PKS 0528+134

ATel #3412; F. D'Ammando (INAF-IASF Palermo and CIFS) on behalf of the Fermi Large Area Telescope Collaboration
on 8 Jun 2011; 12:28 UT
Credential Certification: Filippo D'Ammando (filippo.dammando@iasf-roma.inaf.it)

Subjects: Gamma Ray, >GeV, AGN, Blazar

Referred to by ATel #: 3422

The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope has observed an increasing gamma-ray flux from a source positionally coincident with PKS 0528+134 (also known as 1FGL J0531.0+1331, Abdo et al. 2010, ApJS, 188, 405; R.A.= 05:30:56.4167, Dec.= +13:31:55.150, J2000.0, Johnston et al. 1995, AJ, 110, 880), a flat spectrum radio quasar at redshift z = 2.07 (Hunter et al. 1993, ApJ, 409, 134). PKS 0528+134 was one of the most variable blazars observed by EGRET, with several gamma-ray flaring episodes detected between 1991 and 1996 (Mukherjee et al. 1999, ApJ, 527, 132).

Preliminary analysis indicates that on June 5, 2011, the source was in a high state, with a daily gamma-ray flux (E > 100 MeV) of (1.1 +/- 0.4) x 10^-6 ph cm^-2 s^-1 (statistical uncertainty only), which represents an increase of a factor of 7 with respect to the average source flux observed in the first eleven months of Fermi observations (Abdo et al. 2010, ApJS, 188, 405). This is only the second daily detection of this source by Fermi-LAT since the beginning of the mission (see http://fermi.gsfc.nasa.gov/FTP/glast/data/lat/catalogs/asp/current/lightcurves/PKS0528+134_86400.png ).

Because Fermi operates in an all-sky scanning mode, regular 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 F. D'Ammando (dammando@ifc.inaf.it).

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.