TITLE: GCN CIRCULAR NUMBER: 27043 SUBJECT: LIGO/Virgo S200213t: 1 counterpart neutrino candidate from IceCube neutrino searches DATE: 20/02/13 04:40:26 GMT FROM: Raamis Hussain at IceCube IceCube Collaboration (http://icecube.wisc.edu/) reports: Searches for track-like muon neutrino events detected by IceCube consistent with the sky localization of gravitational-wave candidate S200213t in a time range of 1000 seconds [1] centered on the alert event time (2020-02-13 04:02:20.328 UTC to 2020-02-13 04:19:00.328 UTC) have been performed. During this time period IceCube was collecting good quality data. Two hypothesis tests were conducted. The first search is a maximum likelihood analysis which searches for a generic point-like neutrino source coincident with the given GW skymap [2]. The second uses a Bayesian approach to quantify the joint GW + neutrino event significance, which assumes a binary merger scenario and accounts for known astrophysical priors in the significance estimate, such as GW source distance [3]. 1 track-like event is found in spatial and temporal coincidence with the gravitational-wave candidate S200213t calculated from the map circulated in the 3-Initial notice. This represents an overall p-value of 0.003 (2.75sigma) from the generic transient search and an overall p-value of 0.0174 (2.11 sigma) for the Bayesian search. These p-values measure the consistency of the observed track-like events with the known atmospheric backgrounds. The reported p-values can differ due to the estimated distance of the GW candidate. The distance is used as a prior in Bayesian binary merger search, while it is not taken into account in the generic transient point-like source search. Properties of the coincident events are shown below. dt ra dec Angular Uncertainty(deg) p-value(generic transient) p-value(binary merger) ----------------------------------------------------------------------------------------------------- -175.94 45.21 31.74 0.43 0.003 0.017 where: dt = Time offset (sec) of track event with respect to GW trigger. Angular uncertainty = Angular uncertainty of track event: the radius of a circle representing 90% CL containment by area. Pvalue = the pvalue for this specific track event from each search. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc@icecube.wisc.edu [1] Baret et al., Astroparticle Physics 35, 1 (2011) [2] PoS(ICRC2019)918 Braun et al., Astroparticle Physics 29, 299 (2008) [3] Bartos et al. arXiv:1810.11467 (2018) and Countryman et al.arXiv:1901.05486 (2019)