Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ PKS B0027-024
ATel #17391; F. Longo (University of Trieste and INFN Trieste), A. Holzmann Airasca (University of Trento and INFN Bari) and P. Monti-Guarnieri (University of Trieste and INFN Trieste), on behalf of the Fermi Large Area Telescope Collaboration
on 16 Sep 2025; 17:23 UT
Credential Certification: Francesco Longo (francesco.longo@ts.infn.it)
Subjects: Gamma Ray, >GeV, AGN
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 FSRQ PKS B0027-024, also known as 4FGL J0030.6-0212 (Abdollahi et al. 2022, ApJS, 260, 53), with coordinates R.A. = 7.63260 deg, Dec. = -2.19893 deg (J2000; Hunt et al. 2021, AJ, 162, 121), and redshift z = 1.804 (Sexton et al. 2022, ApJS, 260, 33).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on September 15, 2025, with a daily averaged gamma-ray flux (E>100MeV) of (0.6+/-0.1) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 20 relative to the average flux reported in the fourth data release of the fourth Fermi-LAT catalog (4FGL-DR4, Ballet et al. 2023, arXiv:2307.12546). 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 spectral state than the one inferred from the average power-law spectral index of 2.41 +/- 0.02 reported in 4FGL-DR4. We observed a photon with an energy of 44 GeV with a probability p>0.999 to be associated with the flaring source.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. A preliminary light curve for PKS B0027-024 can be accessed via the Fermi-LAT Light-Curve Repository at 4FGL J0030.6-0212. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Francesco Longo (Francesco.Longo@ts.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.
