Fermi-LAT detection of renewed gamma-ray activity from the high-redshift FSRQ PKS 0537-286
ATel #14285; R. Angioni (SSDC/INFN) on behalf of the Fermi Large Area Telescope Collaboration
on 22 Dec 2020; 19:39 UT
Credential Certification: Roberto Angioni (r.angioni90@gmail.com)
Subjects: Gamma Ray, Request for Observations, AGN, Blazar, Quasar
Referred to by ATel #: 15405
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed renewed gamma-ray flaring activity from a source positionally consistent with the flat-spectrum radio quasar PKS 0537-286, also known as 4FGL J0539.9-2839 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 84.976173 deg, Decl. = -28.665541 deg (J2000; Johnston et al. 1995 AJ, 110, 880), and redshift z=3.104 (Osmer et al. 1994, ApJ, 436, 678).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on 21 December 2020, with a daily averaged gamma-ray flux (E>100MeV) of (1.1+/-0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 25 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL). The corresponding photon index is 2.20+/-0.16, and is significantly smaller compared to the average value recorded in the 4FGL catalog, i.e., 2.73+/-0.04. The current flux is comparable with the one recorded by the LAT during a previous flaring episoide in May 2017 (ATel #10356).
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. This source is included in the "LAT Monitored Sources" and consequently, a preliminary estimation of the daily gamma-ray flux observed by Fermi-LAT will be publicly available ( http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/ ). A Swift ToO proposal has been submitted. We encourage further multifrequency observations of this source. For this source, the Fermi-LAT contact person is C. C. Cheung (teddy.cheung@nrl.navy.mil).
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.
