Fermi LAT detection of renewed GeV gamma-ray activity from the gravitationally lensed blazar PKS 1830-211

ATel #12136; Sara Cutini (INFN-Perugia, Italy), on behalf of the Fermi Large Area Telescope Collaboration
on 21 Oct 2018; 17:38 UT
Credential Certification: David J. Thompson (David.J.Thompson@nasa.gov)

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The Large Area Telescope (LAT), the principal instrument on-board the Fermi Gamma-ray Space Telescope, has observed increasing gamma-ray flux from a source positionally consistent with PKS 1830-211 (also known as 3FGL J1833.6-2103, Acero et al. 2015, ApJS, 218, 2, placed at RA: 18h 33m 39.9s, Dec -21d 03m 40s, J2000, van Ommen et al., 1995, ApJ, 444, 561).

Preliminary analysis indicates that the source on October 18, 2018 showed a significantly increased daily average gamma-ray flux (E>100MeV) of (2.8+/0.3) x10^-6 ph cm^-2 s^-1 (errors are statistical only), more than a factor of 4 greater than the average flux reported in the Third Fermi LAT catalog (3FGL). It was detected also on October 19 with an average flux of of (1.7+/-0.3) x10^-6 ph cm^-2 s^-1. 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/ssc/data/access/lat/msl_lc/ ).

PKS 1830-211 (z=2.507, Lovell et al. 1998, ApJ, 508, L51) is a flat spectrum radio quasar located behind the southern Galactic Bulge with gravitational magnification and absorption features. It is gravitationally lensed by a galaxy at z=0.886 (Wiklind & Combes 1996, Nature, 379, 11). It showed bright GeV gamma-ray flares detected by the LAT in October 2010 (ATel #2943 ), June 2012 (ATel #4158) and in July 2014 (ATel #6361). A gamma-ray flare was also detected by AGILE in October 2009 (ATel #2242).

Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. In consideration of the ongoing activity of this source we encourage multi-wavelength observations. For this source the Fermi-LAT contact person is S. Ciprini (stefano.ciprini@asdc.asi.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.