NGC 1275: Upper limits from a neutrino search with IceCube
ATel #18079; Alicia Mand (University of Wisconsin-Madison), Justin Vandenbroucke (University of Wisconsin-Madison)
on 23 Sep 2026; 21:44 UT
Credential Certification: Justin Vandenbroucke (justin.vandenbroucke@wisc.edu)
The IceCube Collaboration (http://icecube.wisc.edu/) reports:
IceCube has performed a search for track-like muon neutrino events arriving from the direction of the radio galaxy NGC 1275 following reports of an exceptionally bright very-high-energy gamma-ray flare by MAGIC, LST-1 (ATel #18060), and MACE (ATel #18064). We adopt a time window of 20 days to cover the reported enhanced emission phase in gamma rays (2026-09-04 12:00:00.00 UTC to 2026-09-23 12:00:00.00 UTC), during which IceCube was collecting good quality data. IceCube performed a similar search for track-like muon neutrino events from the direction of NGC 1275 a month prior following a previous gamma-ray flare (ATel #18018).
For this search, we report a p-value of 1.0 with respect to an atmospheric background-only hypothesis. We accordingly derive a time-integrated muon-neutrino flux upper limit for this source of E^2 dN/dE = 7.2e-2 GeV cm^-2 at 90% CL, for an E^-2 power law. 90% of events IceCube would detect from a source at this declination with an E^-2 spectrum are between approximately 650 GeV and 350 TeV.
The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc@icecube.wisc.edu.
[1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021)
