Fermi-LAT detection of renewed gamma-ray activity from the radio galaxy NGC 1275
ATel #16988; Pietro Monti-Guarnieri (University Trieste and INFN Trieste) and Denis Bernard (LLR, Ecole Polytechnique & CNRS / IN2P3), on behalf of the Fermi Large Area Telescope Collaboration
on 21 Jan 2025; 17:08 UT
Credential Certification: Denis Bernard (Denis.bernard@in2p3.fr)
Subjects: Gamma Ray, >GeV, AGN, Blazar, Star
Referred to by ATel #: 17020
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 galaxy NGC 1275 also known as Perseus A, 3C 84 and 4FGL J0319.8+4130 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates RA= 49.95067, DEC= 41.51170 (J2000, Beasley et al. 2002, ApJS, 141, 13) and redshift z=0.017559+/-0.000037 (Strauss et al. 1992, ApJS, 83, 29).
We have observed increased activity from that source since November 2024. Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on 2025 January 20, with a daily averaged gamma-ray flux (E>100MeV) of (1.42 +/- 0.25) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of four relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL). The corresponding photon index is 2.01 +/- 0.12, and is consistent with the 4FGL value of 2.12 +/- 0.01 within the uncertainties. This is the fourth time that Fermi is announcing enhanced gamma-ray activity from NGC 1275 (after ATel#2737, ATel#4753, ATel#8219). On the same day, a high-energy photon (36 GeV) was associated with the source at a confidence level p > 0.999.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. A preliminary estimation of the daily gamma-ray flux observed by Fermi-LAT is publicly available ( https://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/source/NGC_1275 ). A preliminary light curve for NGC 1275 can be accessed via the Fermi-LAT Light-Curve Repository at this link. We encourage multifrequency observations of this source. The Fermi LAT contact persons for this source are J. Kataoka (kataoka.jun at waseda.jp) and C.C. Cheung (chi.c.cheung2.civ at us.navy.mil).
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.