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

ATel #13030; S. Buson (Univ. of Wuerzburg, DE; UMBC, USA), D. Constantin (Univ. of Padua, IT) on behalf of the Fermi-LAT Collaboration
on 14 Aug 2019; 19:48 UT
Credential Certification: Sara Buson (sara.buson@gmail.com)

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The Large Area Telescope (LAT), one of the two instruments on board the Fermi Gamma-ray Space Telescope, has observed renewed gamma-ray flaring activity from a source positionally consistent with PKS 1830-211 (also known as 4FGL J1833.6-2103, The Fermi-LAT Collaboration 2019, arXiv:1902.10045), with coordinates RA = 18h 33m 39.9s, Dec = -21d 03m 40s (J2000, van Ommen et al., 1995, ApJ, 444, 561). PKS 1830-211 (z=2.507, Lindman et al. 1999, ApJ, 514, 57) is a flat spectrum radio quasar located behind the southern Galactic Bulge. It is gravitationally lensed by a galaxy at z=0.886 (Wiklind & Combes 1996, Nature, 379, 139).

Preliminary analysis indicates that the source has been undergoing a long-term brightening since October 2018 (ATels #12136 and #12252). On 12 August 2019, PKS 1830-211 reached a daily averaged gamma-ray flux (E>100MeV) of (7.3+/-0.7) X 10^-6 photons cm^-2 s^-1. The observed daily photon index is 2.48+/-0.09 (statistical uncertainty only), compatible with the average index value reported in the 4FGL. The object reached a six-hrs peak flux of (12+/-1) X 10^-6 photons cm^-2 s^-1 on 12 August 2019, between 06:00:00 / 11:17:04 UTC.

The current gamma-ray activity is comparable to that previously reported in ATel #12601 and observed throughout the brightest and longest outburst from PKS 1830-211 recorded by the Fermi-LAT, during March / May 2019. PKS 1830-211 is included in the Fermi-LAT monitored source list; therefore a preliminary estimation of its daily gamma-ray flux observed by Fermi-LAT will be publicly available (http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/).

Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. We encourage further multi-wavelength observations. For this source, the Fermi-LAT contact persons are S. Ciprini (stefano.ciprini@ssdc.asi.it) and S. Buson (sara.buson@gmail.com).

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.