Fermi-LAT detection of renewed gamma-ray activity from the FSRQ OI 280
ATel #17731; Petra Benke (GFZ, MPIfR), on behalf of the Fermi Large Area Telescope Collaboration
on 29 Mar 2026; 21:07 UT
Credential Certification: Petra Benke (pbenke@mpifr-bonn.mpg.de)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Quasar
Referred to by ATel #: 17739
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed renewed gamma-ray activity from a source positionally consistent with the flat-spectrum radio quasar OI 280, also known as 4FGL J0750.8+1229 (Abdollahi et al. 2022, ApJS, 260, 53), with coordinates R.A. = 117.71688 deg, Dec. = +12.51801 deg (J2000; Le Bail et al. 2016, AJ, 151, 3, 79), and redshift z=0.889 (Torrealba et al. 2012, RMxAA, 48, 9).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on March 28, 2026 , with a daily averaged gamma-ray flux (E>100MeV) of (1.5+/-0.4) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of nearly 70 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 2.0+/-0.1, and indicates a harder spectrum than the 4FGL-DR4 value of 2.44 +/- 0.03. In addition, two high-energy photons of 13 GeV and 23 GeV are spatially consistent with this blazar at a confidence level p > 0.999. The Fermi-LAT collaboration has previously reported gamma-ray flaring activity positionally consistent with this source in ATels #17181, #17394, and #17573.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. This source has been added to the "LAT Monitored Sources" and, consequently, a preliminary estimation of the daily gamma-ray flux observed by Fermi-LAT is publicly available at 4FGL J0750.8+1229 . We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Sarah Wagner (sarah.wagner@uni- wuerzburg.de).
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.
