Fermi LAT detection of a very intense and rapid gamma-ray flare from the blazar PKS 1510-089

ATel #3473; F. D'Ammando (INAF-IASF Palermo and CIFS) and D. Gasparrini (ASDC/INAF) on behalf of the Fermi Large Area Telescope Collaboration
on 5 Jul 2011; 22:58 UT
Credential Certification: Filippo D'Ammando (filippo.dammando@iasf-roma.inaf.it)

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The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope, has observed since July 1, 2011, an increasing gamma-ray activity from the flat spectrum radio quasar PKS 1510-089 (also known as 1FGL J1512.8-0906, Abdo et al. 2010, ApJS, 188, 405; R.A. = 15h12m50.5329s, Dec. =-09d05m59.828s, J2000, Johnston et al. 1995, AJ, 110, 880) at redshift z = 0.360 (Thompson et al. 1990, PASP, 102, 1235).

Preliminary analysis indicates that on July 4, 2011 the source reached a gamma-ray flux (E > 100 MeV) of (8.3+/-1.0)e-6 ph cm^-2 s^-1 (statistical uncertainty only) in the daily time scale and a flux of (12.0+/-1.9)e-6 ph cm^-2 s^-1 (statistical uncertainty only) in the 6-hour interval starting at 06:00 UT of the same day. Enhanced gamma-ray emission from this source was recently observed also by AGILE (ATel #3470). This is the fourth time Fermi has reported a gamma-ray flare from this source (Sep 2008, ATel #1743; Jan 2009, ATel #1897; Apr 2009, ATel #2033). The flare reported here represents the highest gamma-ray flux observed from PKS 1510-089 since the beginning of the Fermi mission.

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of these sources will continue. Swift ToO observations were already activated, further multi-wavelength observations are encouraged. The LAT contact persons for this flaring activity are F. D'Ammando (dammando@ifc.inaf.it) and D. Gasparrini (dario.gasparrini@asdc.asi.it). This source 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 (link: http://fermi.gsfc.nasa.gov/FTP/glast/data/lat/catalogs/asp/current/lightcurves/1510-089_86400.png ).

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.