Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ PKS 0215+015
ATel #17452; P. Monti-Guarnieri (University of Trieste and INFN Trieste), E. Bissaldi (Politecnico and INFN Bari), A. Holzmann Airasca (University of Trento and INFN Bari), G. La Mura (INAF - Astronomical Observatory of Cagliari), S. Lopez-Perez (LLR, Ecole Polytechnique & CNRS/IN2P3), on behalf of the Fermi Large Area Telescope Collaboration
on 24 Oct 2025; 15:05 UT
Credential Certification: Giovanni La Mura (giovanni.lamura@inaf.it)
Subjects: Gamma Ray, >GeV, Blazar, Quasar
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 0215+015, also known as 4FGL J0217.8+0144 (Abdollahi et al. 2022, ApJS, 260, 53), with coordinates R.A. = 34.45398 deg, Dec. = +1.74714 deg (J2000; Le Bail et al., 2016, AJ, 151, 79), and redshift z=1.715 (Boisse et al., 1988, A&A, 192, 1-8).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on October 23, 2025, with a daily averaged gamma-ray flux (E>100MeV) of (0.7+/-0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 15 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 1.5+/-0.1, indicating a significantly harder spectrum than the one corresponding to the 4FGL-DR4 value of 2.18+/-0.01. The highest-energy photon associated with the source at a probability p>0.999 had an energy of 25 GeV, and was recorded at 06:35:50.096 UTC on 2025-10-23.
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 0215+015 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_J0217.8+0144. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Pietro Monti-Guarnieri (pietro.monti-guarnieri@phd.units.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.
