Fermi-LAT detection of renewed gamma-ray activity from the gravitationally-lensed FSRQ PKS 1830-211
ATel #15770; S. Garrappa (Ruhr-University Bochum; DESY, Germany), on behalf of the Fermi Large Area Telescope Collaboration
on 21 Nov 2022; 23:00 UT
Credential Certification: Simone Garrappa (simone.garrappa@gmail.com)
Subjects: Gamma Ray, Request for Observations, Blazar
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 2020, ApJS, 247, 33), with coordinates RA = 278.416201, Dec = -21.061048 (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 this source was in an elevated gamma-ray emission state on November 20, 2022, with a daily averaged gamma-ray flux (E>100MeV) of (6.3+/-0.8) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of about 15 with respect to the average value reported in the third release of the Fourth Fermi-LAT source catalogue (4FGL-DR3, Abdollahi et al. 2022, ApJS, 260, 53). The observed daily photon index is 2.4+/-0.1 (statistical uncertainty only), compatible with the average index value of 2.53 +/- 0.01 reported in the 4FGL. The flux of PKS 1830-211 has been progressively increasing since April 2022, similar to the trend observed during the long outburst in 2019 (ATel #13030)
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. This source belongs to the list of daily monitored LAT sources; therefore a preliminary gamma-ray light curve is available at https://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/source/PKS_1830-211. Its light curve can also be accessed through the Fermi-LAT Light Curve Repository (LCR) at https://fermi.gsfc.nasa.gov/ssc/data/access/lat/LightCurveRepository/source.html?source_name=4FGL_J1833.6-2103. We encourage multifrequency observations of this source. 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.
