Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ NRAO 512
ATel #17752; Janeth Valverde (Marquette University), Giovanni La Mura (INAF - Astronomical Observatory of Cagliari), on behalf of the Fermi Large Area Telescope Collaboration
on 13 Apr 2026; 21:37 UT
Credential Certification: Janeth Valverde (valverde@llr.in2p3.fr)
Subjects: Gamma Ray, >GeV, AGN, Blazar
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 NRAO 512, also known as 4FGL J1640.4+3945 (Abdollahi et al. 2022, ApJS, 260, 53), with coordinates R.A. = 250.12347 deg, Dec. = +39.77945 deg (J2000; Xu et al. 2019, ApJS, 242, 1), and redshift z=1.672 (Albareti et al. 2017, ApJS, 233, 2).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state from April 11 to 12, 2026 , with an averaged gamma-ray flux (E>100MeV) of (0.5+/-0.1) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 10 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+/-0.2, slightly harder than the 4FGL-DR4 value of 2.44+/-0.04.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. A preliminary light curve for NRAO 512 can be accessed via the Fermi-LAT Light-Curve Repository at 4FGL J1640.4+3945. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Janeth Valverde (janeth.phd@gmail.com).
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.
