Super-Kamioka Neutrino Detection Experiment (Super-Kamiokande)

Start: 1996

The Super-Kamiokande experiment, also known as Super-K or SK, was built and is operated with funding from the Japanese Ministry of Education, Science, Sports and Culture, and the U.S. Department of Energy. The Hyper-Kamiokande experiment will be the successor of SK. It is expected to start operation around 2028.

GCN Notice Types in GCN Classic and GCN Classic Over Kafka: Detailed Descriptions and Examples

Type	Contents	Latency
`SK_SN`	REAL or TEST supernova alert	~1 min

JSON-Serialized GCN Notices Types in GCN Kafka

Super-Kamiokande GCN schema and example JSON message files are available. See the Schema Browser for more information on the properties defined in the schema. Detailed description and examples of SK Notices are available in the GCN Schema GitHub project.

The information included in the notice published in GCN Kafka are largely overlapping with those in GCN Classic and GCN Classic over Kafka. However, some additional information are also included: the number of detected inverse beta decay (IBD) events, the analysis pipeline used ("snwatch" or "wit"), and the type of processed sample ("full" or "partial") used for event detection.

The alert latency in GCN Kafka is slightly shorter than that in GCN Classic.

Super-Kamiokande specific variables:

alert_datetime: The date and time of the first neutrino detection in the burst of detected neutrino events.
detection_interval: The time interval between the first and last neutrino events [s].
pipeline: The analysis pipeline used to generate this alert; either "snwatch" or "wit". Both the Supernova watch (SNwatch) (Abe et al. 2016) (Kashiwagi et al. 2024) and Wide-band Intelligent Trigger (WIT) (Carminati 2015) (Elnimr and Super-Kamiokande Collaboration 2017) are online analysis systems. The energy thresholds are 6 MeV for SNwatch and 2.5 MeV for WIT, respectively.
processed_sample: Indicates the size of the processed event sample used for this alert; either "full" or "partial".
If the supernova explosion occurs near Earth, a large number of events may be detected by SK. In such cases, an alert may be issued before processing of the full sample is completed, and it will be updated once full processing is finished.
n_events: The total number of detected neutrino events.
n_ibd_events: The number of inverse beta decay (IBD) events in the sample, identified by the coincidence of neutron capture signals.
luminosity_distance and luminosity_distance_error:
The estimated distance to the source and its uncertainty [kpc], assuming a SN1987A-like neutrino flux.
ra_dec_error : The statistical uncertainty of the location [deg]. Its containmaint probalitiy is given as containment_probability (default: 0.68).
trigger_number: Event ID used in GCN Classic.

Kafka topic	Comments
`gcn.notice.superk.sn_alert`	For a real or test supernova alert

Expected Yearly Event Rates:

Type	Rates	Localization	Latency
Core-collapse supernova	0.03	5–10°	~1 min
Test alert	12 (monthly)	5–10°	N/A

Bibliography

Abe, K., Y. Haga, Y. Hayato, M. Ikeda, K. Iyogi, J. Kameda, Y. Kishimoto, et al. 2016. “Real-Time Supernova Neutrino Burst Monitor at Super-Kamiokande.” Astroparticle Physics 81 (August): 39–48. https://doi.org/10.1016/j.astropartphys.2016.04.003.

Carminati, Giada. 2015. “The New Wide-Band Solar Neutrino Trigger for Super-Kamiokande.” Physics Procedia 61 (January): 666–72. https://doi.org/10.1016/j.phpro.2014.12.068.

Elnimr, Muhammad, and Super-Kamiokande Collaboration. 2017. “Low Energy ⁸ B Solar Neutrinos with the Wideband Intelligent Trigger at Super-Kamiokande.” In Journal of Physics Conference Series, 888:012189. Journal of Physics Conference Series. https://doi.org/10.1088/1742-6596/888/1/012189.

Kashiwagi, Y., K. Abe, C. Bronner, Y. Hayato, K. Hiraide, K. Hosokawa, K. Ieki, et al. 2024. “Performance of SK-Gd’s Upgraded Real-Time Supernova Monitoring System.” Astrophysical Journal 970 (1): 93. https://doi.org/10.3847/1538-4357/ad4d8e.