Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ PKS 2332-017
ATel #16345; Federica Giacchino (INFN Sezione Roma TorVergata & ASI Science Data Center, Italy) on behalf of the Fermi Large Area Telescope Collaboration
on 22 Nov 2023; 22:41 UT
Credential Certification: Federica Giacchino (federica.giacchino@roma2.infn.it)
Subjects: Gamma Ray, >GeV, AGN, Quasar
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed a gamma-ray flare from a source positionally consistent with the flat-spectrum radio quasar PKS 2332-017, also known as 4FGL J2335.4-0128 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 353.901 deg, Decl. = -1.498 deg (J2000; Johnston et al. 1995, AJ, 110, 880), and redshift z=1.182 (Ajello et al. 2022, ApJS, 263,9).
A dedicated analysis indicates that this source was in an elevated gamma-ray emission state on November 20, 2023, with a daily averaged gamma-ray flux (E>100MeV) of (0.61 +/- 0.14) x 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 110 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL). This is the highest LAT daily flux ever observed for this source. The photon index is 2.26 +/- 0.18, corresponding to a harder spectrum than the 4FGL value of 2.47 +/- 0.09. This is the first report of enhanced activity from PKS 2332-017, although inspection of the https://fermi.gsfc.nasa.gov/ssc/data/access/lat/lcr/source.html?source_name=4FGL_J2335.4-0128 indicates that it has been moderately active in recent weeks.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. We encourage multifrequency observations of this source, especially in light of the large redshift and hard spectrum. For this source, the Fermi-LAT contact person is Federica Giacchino (federica.giacchino@roma2.infn.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.
