TITLE: GCN CIRCULAR NUMBER: 25297 SUBJECT: LIGO/Virgo S190808ae: One Coincident Neutrino Candidate from IceCube Search DATE: 19/08/08 23:53:52 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 S190808ae in a time range of 1000 seconds [1] centered on the alert event time (2019-08-08 22:13:01.496 UTC to 2019-08-08 22:29:41.496 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]. One track-like event is found in spatial and temporal coincidence with the gravitational-wave candidate S190808ae calculated from the map circulated in the 2-Initial notice. This represents an overall p-value of 0.0448 (1.70 sigma) from the generic transient search and an overall p-value of 0.068 (1.49 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 the Bayesian binary merger search, while it is not taken into account in the generic transient point-like source search. Properties of the coincident event are shown below. dt | ra (deg) | dec (deg) | Angular Uncertainty(deg) | p-value(generic transient) | p-value(bayesian) -----+--------+---------+------------------------+------------------+-------------------------- -37 | 216.29 |-15.35 | 0.43 |0.045 |0.070 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. p-value = the p-value for this specific track event from each search. RA & Dec = Right ascension and declination in degrees quoted in J2000 epoch 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] Braun et al., Astroparticle Physics 29, 299 (2008) [3] Bartos et al. arXiv:1810.11467 (2018) and Countryman et al.arXiv:1901.05486 (2019)```