Record gamma-ray flux level detected from PKS 1510-089 by Fermi/LAT

ATel #3694; F. Hungwe (Rhodes U, HartRAO), M. Dutka (Catholic U) & R. Ojha (NASA/GSFC), on behalf of the Fermi Large Area Telescope Collaboration
on 20 Oct 2011; 17:04 UT
Credential Certification: Roopesh Ojha (Roopesh.Ojha@gmail.com)

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The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope, has observed a sharp increase in the gamma-ray flux of the flat spectrum radio quasar PKS 1510-089 (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 shows that the enhanced gamma-ray activity began on 17 October 2011 with a gamma-ray flux of 6e-6 ph cm^-2s^-1 (E>100MeV), reaching a maximum of (15.9+/-1.0) e-6 ph cm^-2 s^-1 in the daily run and (30.1 +/- 2.3)e-6 ph cm^-2 s^-1 in the six hour run that began at 18:00 hrs UT on 19 October 2011. This is the highest gamma-ray flux ever reported for this source. The last time Fermi reported this source to be flaring was in July 2011 (ATel #3473), when it reached a flux of (8.3+/-1.0)e-6 ph cm^-2 s^-1. The current flare compares to a flux of (56 +/- 4)x10-6 photons cm-2 s-1 reached by 3C454.3 in Nov 2010 (ATel #3041) making this the second brightest AGN observed by LAT.

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of the source will continue. At the moment, the source is only 23 degrees from the Sun thus too close to be observed by Swift but other multi-wavelength observations are encouraged. The LAT contact persons for this flaring activity are Filippo D’Ammando (dammando@ifc.inaf.it) and Dario 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.