Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ PKS B2258-022

ATel #16815; Adithiya Dinesh (UCM, Madrid), Denis Bernard (LLR, Ecole Polytechnique & CNRS / IN2P3), on behalf of the Fermi LAT Collaboration
on 16 Sep 2024; 12:44 UT
Credential Certification: David J. Thompson (David.J.Thompson@nasa.gov)

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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 B2258-022, also known as 4FGL J2301.0-0158 (4FGL-DR4; Ballet et al. 2024, arXiv:2307.12546), with coordinates R.A. = 345.283242 deg, Decl. = -1.967941 deg (J2000; Beasley et al. 2002, ApJS, 141, 13), and redshift z=0.778 (Jackson et al. 2002, A&A, 386, 97).

Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on September 10, 2024, 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 about 30 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 2.16+/-0.16, and is consistent with the 4FGL value of 2.34 +/- 0.02 within the uncertainties.

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/ ). A preliminary light curve for PKS B2258-022 can be accessed via the Fermi-LAT Light Curve Repository at https://fermi.gsfc.nasa.gov/ssc/data/access/lat/LightCurveRepository/source.html?source_name=4FGL_J2301.0-0158. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Adithiya Dinesh (adinesh[at]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. Like Be the first to like this