{
"subject": "LIGO/Virgo S191216ap: 1 counterpart neutrino candidate from IceCube neutrino searches",
"bibcode": "2019GCN.26460....1I",
"createdOn": 1576540357000,
"circularId": 26460,
"submitter": "Raamis Hussain at IceCube ",
"email": "raamis.hussain@icecube.wisc.edu",
"body": "IceCube Collaboration (http://icecube.wisc.edu/) reports:\n\nSearches for track-like muon neutrino events detected by IceCube consistent\nwith the sky\n\nlocalization of gravitational-wave candidate S191216ap in a time range of\n1000 seconds [1]\n\ncentered on the alert event time (21:25:18.473 UTC to 21:41:58.473 UTC)\nhave been performed.\n\nUp until 21:33:21 UTC IceCube was collecting good quality data, at which\npoint power issues at the experimental site caused issues with data\nquality. Only neutrino candidates collected before this time are\nconsidered. Two hypothesis tests were conducted. The first search is a\nmaximum likelihood analysis which searches for a generic point-like\nneutrino source coincident with the given GW skymap [2]. The second uses a\nBayesian approach to quantify the joint GW + neutrino event significance,\nwhich assumes a binary merger scenario and accounts for known astrophysical\npriors in the significance estimate, such as GW source distance [3].\n\n1 track-like event is found in spatial and temporal coincidence with the\ngravitational-wave\n\nCandidate S191216ap calculated from the map circulated in the 2-Initial\nnotice. This\n\nrepresents an overall p-value of 0.104 (1.26 sigma) from the generic\ntransient search\n\nand an overall p-value of 0.0059 (2.52 sigma) for the Bayesian search.\nThese p-values\n\nmeasure the consistency of the observed track-like events with the known\natmospheric backgrounds. Both analyses assume 100% livetime during the\nsearch window; the statistical significances are therefore lower limits.\n\nThe reported p-values can differ due to the estimated distance of the GW\ncandidate. The distance is used as a prior in Bayesian binary merger\nsearch, while it is not taken into account in the generic transient\npoint-like source search.\n\nProperties of the coincident event are shown below.\n\n dt ra(deg) dec(deg) Angular Uncertainty(deg) p-value(generic\ntransient) p-value(binary merger)\n\n--------------------------------------------------------------------------------------------------------------------\n\n -43s 329.19 4.53 4.07 0.219 0.0059\n\n\nwhere:\n\ndt = Time offset (sec) of track event with respect to GW trigger.\n\nAngular uncertainty = Angular uncertainty of track event: the radius of a\ncircle\n\n representing 90% CL containment by area.\n\nPvalue = the pvalue for this specific track event from each search.\n\n\nThe IceCube Neutrino Observatory is a cubic-kilometer neutrino detector\noperating at the\n\ngeographic South Pole, Antarctica. The IceCube realtime alert point of\ncontact can be\n\nreached at roc@icecube.wisc.edu\n\n[1] Baret et al., Astroparticle Physics 35, 1 (2011)\n\n[2] PoS(ICRC2019)918, Braun et al., Astroparticle Physics 29, 299 (2008)\n\n[3] Bartos et al. arXiv:1810.11467 (2018) and Countryman et\nal.arXiv:1901.05486 (2019)"
}