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Fermi LAT detection of gamma-ray re-brightening of blazar PKS1510-089

ATel #2033; S. Cutini (ASDC) and E. Hays (NASA/GSFC) on behalf of Fermi LAT collaboration
on 26 Apr 2009; 22:42 UT
Credential Certification: Paolo Giommi (paolo.giommi@asi.it)

Subjects: Gamma Ray, AGN

Referred to by ATel #: 2045, 3470, 3473

The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope (formerly GLAST, launched June 11, 2008), has observed, since April 25th, 2009, a flare from a gamma-ray source positionally consistent with the blazar PKS 1510-089 (RA:15h12m50.5329s, Dec:-09d05m59.828s, redshift 0.360 and already known as an EGRET gamma-ray source, 3EG J1512-0849). Preliminary analysis indicates that on 25th April the source was in a high state with a gamma-ray flux (E>100MeV) of 6.5+/-0.7e-6 cm^-2 s^-1 (statistical only) in the daily time scale and it reached a value of 8.2+/-1.9e-6 cm^-2 s^-1 (statistical only) in the 6-hours interval starting at 06:00 UT of the same day. This is the third time that Fermi is observing and announcing a similar GeV flare of this blazar (January 2009, ATEL#1897 and September 2008, ATEL#1743). During the first hours of April 26, 2009 the source shows hints of increasing flux reaching a value greater then 12 times the average of previous months. This blazar is classified as a Flat Spectrum Radio Quasar (FSRQ), and it is rather bright in the optical bands, allowing an easier ground-based follow up. Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. PKS 1510-089 is one of the "LAT Monitored Sources" and consequently a preliminary estimation of the daily gamma-ray flux observed by Fermi LAT is publicly available (http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/). In consideration of the ongoing activity of this source we strongly encourage multiwavelength observations. For this source the Fermi LAT contact person is A. Tramacere (tramacer@slac.stanford.edu). 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.