Status of Realtime Neutrino Alerts in IceCube

Parallel talk presented at the XXI International Workshop on Neutrino Telescopes - Padova 29 September - 3 October 2025

(https://agenda.infn.it/event/44606/)

On behalf of the IceCube Collaboration

Abstract:

Neutrino astronomy benefits from multimessenger collaboration, particularly in the search for time-variable astrophysical sources. Identifying statistically significant astrophysical neutrino flares amid a sea of atmospheric muon and neutrino background remains challenging. In the case of a true neutrino flare, coincident detections of electromagnetic activity can strengthen the case for an astrophysical origin. The IceCube neutrino observatory nearly continuously monitors the full sky making it well suited to provide targets of opportunity for follow-up by pointed instruments. Given this, IceCube has implemented a realtime program that provides neutrino alerts to the multimessenger community. These alerts fall into three major categories: single high-energy event alerts, multiple-event (or cluster) alerts, and rapid follow-up analyses of interesting transient phenomena. A major milestone of this program was the observation of a multiwavelength flare from the blazar TXS 0506+056, triggered by an IceCube alert from a single, high-energy neutrino event. In this presentation, we will provide an overview of the realtime program and highlight recent efforts to update IceCube’s cluster alerts.