Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ PKS B2258-022
ATel #16952; Omer Faruk Coban (Institute of Space Sciences, ICE-CSIC), Giovanni La Mura (INAF - O. A. Cagliari), on behalf of the Fermi Large Area Telescope Collaboration
on 15 Dec 2024; 21:14 UT
Credential Certification: Giovanni La Mura (glamura@lip.pt)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar, Quasar
Referred to by ATel #: 16953
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 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 345.28324 deg, Decl. = -1.96794 deg (J2000; Hunt et al. 2021, AJ, 162, 18), and redshift z=0.777 (Albareti et al. 2017, ApJS, 233, 25).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on December 14, 2024, with a daily averaged gamma-ray flux (E>100MeV) of (1.3+/-0.3) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This value is about 40 times larger than 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 1.8+/-0.1, indicating a significantly harder spectrum than the 4FGL value of 2.34+/-0.02. Two high-energy (>10 GeV) photons were associated with the source at a confidence level p > 0.999. The highest energy event was a 45 GeV photon observed on December 14 at 11:47:45 UT. The Fermi-LAT Collaboration has previously reported flaring activity from this source in ATels #7445 and #16815.
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 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 Monica Orienti (orienti@ira.inaf.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.
