GCN Circular 45768
GRB 260924A: Upper limits from a neutrino search with IceCube
From: Sam Hori at IceCube/U Wisc-Madison
Issued: 2026-09-27 00:54 UTC

The IceCube Collaboration (http://icecube.wisc.edu/) reports:

IceCube has performed a search for track-like muon neutrino events arriving from the direction of GRB 260924A (GCN 45712) at the position determined by NOT observations of the afterglow (GCN 45718) in a time range of (-1 hour, +2 hours) from the initial trigger (GCN 45723) reported by Fermi-GBM (T0=2026-09-24 01:13:23.56 UTC) during which IceCube was collecting good quality data.

Zero track-like events are found to coincide with the position of the GRB. We accordingly derive a time-integrated muon-neutrino flux upper limit of E^2 dN/ dE = 3.5e-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 have energies between approximately 940 GeV and 1.6 PeV.

A subsequent search was performed including 2 days of data centered on the Fermi-GBM trigger (2026-09-23 01:13:23.56 UTC to 2026-09-25 01:13:23.56 UTC). In this search, we report a p-value of 1.0, consistent with background expectation. We accordingly derive a time-integrated muon neutrino flux upper limit of E^2 dN/ dE = 4.1e-2 GeV cm^-2 at 90% CL, under the assumption of an E^-2 power law.

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)

Filter: gamma-ray bursts are posted only if in the top 10% of the past year's — by fluence (total energy received per cm², from Fermi GBM, Konus-Wind, GECAM and similar circulars; now ≥ 3.9×10^-5 erg/cm²) or by the number of GCN Circulars about the burst (now ≥ 14). Thresholds are recalculated monthly.
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