Fermi-LAT detection of renewed gamma-ray activity from the Radio-Loud Narrow-Line Seyfert 1 1H 0323+342
ATel #17407; F. Longo (University of Trieste and INFN Trieste), A. Holzmann Airasca (University of Trento and INFN Bari) and G. La Mura (INAF - Astronomical Observatory of Cagliari) on behalf of the Fermi Large Area Telescope Collaboration
on 21 Sep 2025; 19:32 UT
Credential Certification: Francesco Longo (francesco.longo@ts.infn.it)
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 renewed gamma-ray activity from a source positionally consistent with the radio-loud narrow-line Seyfert 1 1H 0323+342, also known as 4FGL J0324.8+3412 (Abdollahi et al. 2022, ApJS, 260, 53), with coordinates R.A. = 51.17150 deg, Dec. = 34.17941 deg (J2000; Hunt at al. 2021, AJ 162, 121), and redshift z=0.0629 (Zhou et al. 2007, ApJ 658, L13).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on September 20, 2025 with a daily averaged gamma-ray flux (E>100MeV) of (0.9+/-0.2) 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). The corresponding photon index is 2.9+/-0.2, and is consistent with the 4FGL-DR4 value of 2.82+/-0.03 within the uncertainties. The Fermi LAT Collaboration has previously reported flaring activity from this source in ATel #5344.
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 this link. A preliminary light curve for 1H 0323+342 can also be accessed via the Fermi-LAT Light-Curve Repository at 4FGL J03424.8+3412. 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.
