Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ PKS 0915-213
ATel #16797; Adithiya Dinesh (UCM, Madrid), Denis Bernard (LLR, Ecole Polytechnique & CNRS / IN2P3), on behalf of the Fermi Large Area Telescope Collaboration
on 2 Sep 2024; 08:30 UT
Credential Certification: Denis Bernard (Denis.bernard@in2p3.fr)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed enhanced gamma-ray activity from a source positionally consistent with the flat-spectrum radio quasar PKS 0915-213, also known as 4FGL J0917.1-2131 (4FGL-DR4; Ballet et al. 2024, arXiv:2307.12546), with coordinates R.A. = 139.362568 deg, Decl. = -21.526239 deg (J2000; Beasley et al., 2002 ApJS, 141, 13), and redshift z=0.847 (Wright et al., 1979 ApJ, 229, 73).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on August 29, 2024, with a daily averaged gamma-ray flux (E>100MeV) of (0.2+/-0.1) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 40 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 corresponding photon index is 1.9+/-0.3, and is significantly smaller than the 4FGL value of 2.4+/-0.1.
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. For this source, the Fermi-LAT contact person is Adithiya Dinesh (adinesh@ucm.es).
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.
