GCN Circular 43419

The IceCube Collaboration announces that, starting on IceCube-260115A, IceCube’s real-time GCN Notices for high-energy track alerts (Gold and Bronze alerts) are being streamed via the GCN Kafka system, for both preliminary and revised reconstructions.

During an initial transition period, IceCube alerts will be distributed simultaneously through both the classic GCN system (via AMON; https://gcn.gsfc.nasa.gov/amon_icecube_gold_bronze_events.html) and GCN over Kafka. This dual-distribution phase is intended to ensure continuity for existing subscribers while enabling the community to migrate to the new Kafka-based infrastructure. After this transition period, alert dissemination will fully switch to GCN Kafka; a further announcement will follow.

The transition to GCN Kafka introduces important new features for IceCube alerts:

1. Release of multi-order probability sky maps

For each revised alert reconstruction (Revision 1), IceCube now provides a multi-order probability map (MOC/HEALPix; https://gcn.nasa.gov/docs/sample/healpix) describing the directional probability distribution of the neutrino event. These maps were not available through the previous alert system and include both statistical and systematic uncertainties, with probability density expressed in units of 1/sr.

2. Updated calculation of astrophysical probability and false-alarm rate

With GCN Kafka, the reported astrophysical probability (now denoted p_astro, previously referred to as signalness) and false-alarm rate (FAR) are recalculated using the revised best-fit event direction provided in the updated reconstruction (associated with the second GCN Notice). In the previous system, these quantities were reported using values from the preliminary reconstruction and were not updated after directional refinement.

We encourage all users of IceCube real-time alerts to begin subscribing to the Kafka topic = gcn.notices.icecube.gold_bronze_track_alerts

IceCube Gold/Bronze alerts now follow this GCN schema structure.

Detailed documentation describing the alert distribution, schemas, and probability maps will be available soon at: https://gcn.nasa.gov/missions/icecube

Questions regarding IceCube alerts may be directed to the IceCube Collaboration.

The IceCube real-time alert point of contact can be reached at roc@icecube.wisc.edu.