Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ B3 0227+403

ATel #17890; F. Casaburo (INAF-OAR, INFN Roma Tor Vergata, Sapienza University of Roma), S. Ciprini (INFN Roma Tor Vergata, ASI-SSDC), on behalf of the Fermi Large Area Telescope Collaboration
on 13 Jul 2026; 21:42 UT
Credential Certification: Giovanni La Mura (giovanni.lamura@inaf.it)

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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 (FSRQ) B3 0227+403, also known as 4FGL J0230.8+4032 (Abdollahi et al. 2022, ApJS, 260, 53), with coordinates R.A. = 37.69046 deg, Dec. = +40.54808 deg (J2000; Abdollahi et al. 2022, ApJS, 260, 53), and redshift z= 1.019 (Henstock et al. 1997, MNRAS, 290, 380).

Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on July 12, 2026, with a daily averaged gamma-ray flux (E>100MeV) of (0.3+/-0.1) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of nearly 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 2.1+/-0.3 and is consistent with the 4FGL-DR4 value of 2.45+/-0.03 within the uncertainties.

Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. A preliminary light curve for B3 0227+403 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_J0230.8+4032. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Fausto Casaburo (fausto[dot]Casaburo[at]roma2[dot]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.