Identifying multiplets of IceCube alert events

Abstract

The IceCube Neutrino Observatory publishes "alert events", i.e. detections of high-energy neutrinos with a moderate-to-high probability of being of astrophysical origin. While some events are produced in the atmosphere, a fraction of alert events should point back to their astrophysical sources. We aim to identify multiple alert events possibly related to a single astrophysical counterpart by searching for spatial and temporal clusterings in 13 years of alert data. We identify spatial clusters ("multiplets") by checking for events overlapping within their uncertainty regions. In order to reduce chance coincidences and to improve the signal purity of our sample, we apply different thresholds. We investigate the weighted mean position of these multiplets for an over-fluctuation of gamma-ray counterparts. As a final step, we apply expectation maximization to search for temporal clusters around the identified weighted mean positions. We find no statistically significant clustering of alert events around a specific origin direction or in time. This could be because the selections are still dominated by atmospheric background. Another possibility is that we are not yet sensitive enough and only detect single events from sources. In this case, we need more data in order to observe a clustering of events around their origin.

8 pages, 7 figures. Accepted for publication in A&A on 5 March 2025

References in corpus (23)

• Multi-messenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A
• Neutrino emission from the direction of the blazar TXS 0506+056 prior to the IceCube-170922A alert
• Evidence for neutrino emission from the nearby active galaxy NGC 1068
• Observation of high-energy neutrinos from the Galactic plane
• Improved Characterization of the Astrophysical Muon-Neutrino Flux with 9.5 Years of IceCube Data
• Constraining High-Energy Cosmic Neutrino Sources: Implications and Prospects
• The IceCube Realtime Alert System
• Observational evidence for the origin of high-energy neutrinos in parsec-scale nuclei of radio-bright active galaxies
• Dissecting the regions around IceCube high-energy neutrinos: growing evidence for the blazar connection
• IceCat-1: the IceCube Event Catalog of Alert Tracks
• Very High-Energy Gamma-Ray Follow-Up Program Using Neutrino Triggers from IceCube
• Growing evidence for high-energy neutrinos originating in radio blazars
• Searching for soft relativistic jets in Core-collapse Supernovae with the IceCube Optical Follow-up Program
• Multiwavelength follow-up of a rare IceCube neutrino multiplet
• Detection of a Type IIn Supernova in Optical Follow-up Observations of IceCube Neutrino Events
• The neutrino background from non-jetted active galactic nuclei
• The Spectra of IceCube Neutrino (SIN) candidate sources -- V. Modeling and interpretation of multiwavelength and neutrino data
• Two 100 TeV neutrinos coincident with the Seyfert galaxy NGC 7469
• Association of the IceCube neutrinos with blazars in the CGRaBS sample
• Search for Continuous and Transient Neutrino Emission Associated with IceCube's Highest-Energy Tracks: An 11-Year Analysis
• $Fermi$-LAT follow-up observations in seven years of real-time high-energy neutrino alerts
• The Spectra of IceCube Neutrino (SIN) candidate sources -- IV. Spectral energy distributions and multi-wavelength variability
• Fast Identification of Transients: Applying Expectation Maximization to Neutrino Data