Detection of an exceptionally bright VHE gamma-ray flare from the radiogalaxy NGC 1275 with MAGIC and LST-1

ATel #18060; David Paneque (Max Planck Institute for Physics), Mireia Nievas Rosillo (IAC), Sami Caroff (LAPP), Mario Pecimotika (IFAE), Axel Arbet-Engels (University of Geneva), Jorge Otero Santos (INFN Padova) on behalf of the MAGIC and CTAO-LST collaborations
on 19 Sep 2026; 11:49 UT
Credential Certification: David Paneque (dpaneque@mpp.mpg.de)

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The MAGIC and CTAO LST Collaborations report the detection of very-high-energy (VHE; E>100 GeV) gamma-ray emission from NGC 1275 (a.k.a. 3C 84, R.A. 49.95 deg, Dec. +41.51 deg, J2000.0). The preliminary analysis of the MAGIC data taken on the nights of September 16 and 17 resulted in the detection of NGC 1275 with a highly significant signal after about 5.6 hours of observations. The LST-1 telescope observed simultaneously, and a preliminary analysis further confirms the highly significant detection. Our preliminary results indicate an increase in the VHE gamma-ray activity above 100 GeV by a factor of >40 with respect to its average emission of ~0.025 Crab Units, as reported in the TeVCat (https://www.tevcat.org/). LST-1 and MAGIC Observations from the past two nights (September 18 and 19) reveal that the strong flaring activity is till ongoing.

NGC 1275 is a radiogalaxy located in the Perseus Cluster at redshift z=0.0176 (Strauss et al., 1992, Astrophysical Journal Supplement v.83, p.29). The source has been detected in a high emission state by our Fermi-LAT monitoring pipelines FlaapLUC (Lenain, 2018, Astronomy and Computing, Volume 22, p. 9-15) and Flaschep, revealing several high-energy (E>10 GeV) photons and a gamma-ray spectral index ~2. The MAGIC and LST-1 observations were triggered by this flaring activity in gamma-rays.

MAGIC and LST-1 observations on NGC 1275 will continue during the next few days. Follow-up observations (gamma-rays, X-rays, optical, NIR, radio) are strongly encouraged. The contact persons for these observations are David Paneque (dpaneque@mpp.mpg.de), Masahiro Teshima (mteshima@mpp.mpg.de) and Mireia Nievas Rosillo (mireia.nievas@iac.es).

The preliminary analysis has been performed by Mireia Nievas Rosillo (MAGIC), Sami Caroff and Mario Pecimotika (LST-1). The observations were performed by the operators on site: Jorge Buces Sáez, Rosamaria Carraro, Mykhailo Dalchenko, Susmita Das, Pawel Gliwny, Gevorg Harutyunyan, Lorena Lulić, Marina Manganaro, Dimitris Maniadakis, Toni Marante, Abhradeep Roy. MAGIC is a system of two 17m-diameter Imaging Atmospheric Cherenkov Telescopes located at the Canary island of La Palma, Spain, and designed to perform gamma-ray astronomy in the energy range from 50 GeV to greater than 50 TeV. LST-1 is the first Large-Sized Telescope of the Cherenkov Telescope Array Observatory, and is located on the Canary island of La Palma, Spain. The telescope design is optimized for observation of gamma rays in the range from 20 GeV to 3 TeV.