Fermi-LAT detection of enhanced gamma-ray activity from the radio source 7C 2238+5117
ATel #16661; Adithiya Dinesh (Universidad Complutense de Madrid), Denis Bernard (LLR, Ecole Polytechnique & CNRS / IN2P3), on behalf of the Fermi Large Area Telescope Collaboration
on 18 Jun 2024; 15:36 UT
Credential Certification: Janeth Valverde (valverde@llr.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 blazar 7C 2238+5117, also known as 4FGL J2240.4+5133 in the fourth Fermi-LAT catalog (4FGL) Data Release 4 (4FGL-DR4; Ballet et al. 2024, arXiv:2307.12546), with coordinates R.A. = 340.0828 deg, Dec = +51.5533 deg (J2000; Beasley, A. J et al., 2002 ApJS, 141, 13), and unknown redshift.
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on 2024 June 12 , with a daily averaged gamma-ray flux (E>100MeV) of (1.7+/-0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 240 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 2.2+/-0.1, and is significantly harder than the 4FGL value of 2.50+/-0.07.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. This source is being added to 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/ ). 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.
