IceCube Neutrino Observatory

Construction Completion Date: December 2010

End of Operations: No specific requirement

Data Archives:

• Dataverse
• Data Releases
• HEASARC

The IceCube Neutrino Observatory is a cubic-kilometer Cherenkov particle detector deployed in the Antarctic ice beneath the Amundsen-Scott South Pole Station. It consists of 86 strings of photo-detectors, extending to a depth of about 2,500 meters below the glacier's surface and instrumenting a cubic-kilometer of ice. The Digital Optical Module photo-detectors detect the light produced by relativistic charged particles produced by neutrino interactions in or near the instrumented volume of ice.

IceCube is sensitive to neutrinos from all directions. As neutrinos pass through the ice, their interactions can leave track signatures (~km in length) in the IceCube detector array when they produce secondary muons or compact signatures (cascades of ~m in extent) when they produce secondary electrons or hadrons. Track events can be reconstructed with an uncertainty of less than 1 degree, while cascade events have higher signal purity. IceCube triggers on signals for neutrino energies greater than ~10 GeV (10¹⁰ eV) and can identify likely astrophysical neutrino events for neutrino energies greater than ~50 TeV (5×10¹³ eV) and issue alerts to the community.

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

GCN Notice Types in GCN Classic and GCN Classic Over Kafka

IceCube has been sending alerts generated by realtime on astrophysical neutrino searches^{1 2} over the GCN classic system through the Astrophysical Multimessenger Observatory Network (AMON). Work is underway to update and transition these to the new GCN Kafka system. Detailed Descriptions and Examples are available.

GCN Notice Types in GCN Over Kafka

IceCube LVK Alert Nu Track Search
topic = gcn.notices.icecube.lvk_nu_track_search
IceCube performs realtime searches for coincident neutrino signals with all LIGO/Virgo/KAGRA gravitational-wave alerts, using a realtime muon neutrino track event selection³ and the sky maps from gravitational wave detectors. These low-latency joint searches identify neutrino signals within a ±500 second time window surrounding the LVK alert time, and aim to identify multi-messenger transient sources and seed electromagnetic followup up observations^{4 5}.

These searches are performed as quickly as possible, as soon as the realtime neutrino information for the 1000 second window are available, and are repeated for each update to the LVK alert information. The results from each repeated search will sent as a GCN notice, including identifying information to the corresponding LVK alert version. Results from all searches in LVK Runs 03 and 04 are available on the IceCube Realtime Gravitational Wave Followup page

For high-significance LVK alerts, two hypothesis tests are conducted. The first search is a maximum likelihood analysis which searches for a generic point-like neutrino source coincident with the given GW sky map. The second uses a Bayesian approach⁶ to quantify the joint GW + neutrino event significance, which assumes a binary merger scenario and accounts for known astrophysical priors, such as GW source distance, in the significance estimate. For low-significance LVK alerts, only the Bayesian search is performed. All searches are reported via GCN Notices over Kafka, and any coincident observation with a observed p-value less than 1% will also be sent as a GCN Circular.

The GCN Notice will highlight:

• Overall search results p-values for the generic and Bayesian searches ('pval_generic' and 'pval_bayesian')
• If the analysis p-value from either search is less than 10%, the number ('n_events_coincident') and per-event information for coincident neutrino events (for events with a per-event p-value of less than 10%) are also provided:
  • 'event_dt' - relative timing of neutrino to GW alert (sec)
  • 'ra', 'dec' - reconstructed neutrino event direction (deg., J200),
  • 'ra_uncertainty' - circular direction error (deg.) at 90% confidence.
  • 'event_pval_generic', 'event_pval_bayesian' - per-event p-values for each search. In the case of multiple coincidences, can be used to determine relative importance of each event to search results.
• 'most_probable_direction' - RA/DEC (deg., J2000) for the most likely direction from the generic neutrino source coincidence search.
• 'neutrino_flux_sensitivity_range' - Time integrated flux sensitivity range (min, max) [GeV cm^-2] and energy sensitivity range (lower, upper) [GeV], assuming an E^-2 neutrino spectrum (E² dN/dE) found within the points in the 90% region of GW map localization"

The GCN schema and example JSON message files are available to use. See our Schema Browser for more information on the properties defined in the schema.

Please note: The reported p-values here do not account for any trials correction (multiple hypotheses testing). The false alarm rate of these coincidences can be obtained by multiplying the p-values with their corresponding GW trigger rates. All neutrino searches performed to date for Run O3 and O4 are cataloged on the IceCube Realtime Gravitational Wave Followup page. Rate estimates and more information on the LVK alerts can be found in the LIGO/Virgo/KAGRA Public Alerts User Guide.

Common GCN Circular Types

Yearly Alert Rates

IceCube Acknowledges

The IceCube Neutrino Observatory is funded and operated primarily through an award from the National Science Foundation to the University of Wisconsin–Madison. The IceCube Collaboration, with over 350 scientists in 58 institutions from around the world, runs an extensive scientific program that has established the foundations of neutrino astronomy. See the full list of institutions.

IceCube’s research efforts, including critical contributions to the detector operation, are funded by agencies in Australia, Belgium, Canada, Denmark, Germany, Italy, Japan, New Zealand, Republic of Korea, Sweden, Switzerland, Taiwan, the United Kingdom, and the United States including the NSF. IceCube construction was also funded with significant contributions from the National Fund for Scientific Research (FNRS & FWO) in Belgium; the Federal Ministry of Education and Research (BMBF) and the German Research Foundation (DFG) in Germany; the Knut and Alice Wallenberg Foundation, the Swedish Polar Research Secretariat, and the Swedish Research Council in Sweden; and the Wisconsin Alumni Research Foundation in the U.S.

Footnotes

1. M.G. Aartsen, et al. (2017) Astropart. Phys., 92, 30 (10.1016/j.astropartphys.2017.05.002) ↩

2. R. Abbasi, et al. (2023) https://arxiv.org/abs/2304.01174 ↩

3. M. G. Aartsen et al. (2016) JINST 11 P11009 (10.1088/1748-0221/11/11/P11009) ↩

4. M. G. Aartsen et al. (2020) ApJL 898 L10 (10.3847/2041-8213/ab9d24) ↩

5. R. Abbasi et al. (2023) ApJ 944 80 (10.3847/1538-4357/aca5fc) ↩

6. I. Bartos et al. (2019) Phys. Rev. D 100, 083017 (10.1103/PhysRevD.100.083017) ↩