{
  "bibcode": "2025GCN.39176....1I",
  "eventId": "LIGO/Virgo/KAGRA S250206dm",
  "circularId": 39176,
  "submittedHow": "web",
  "createdOn": 1738881412136,
  "format": "text/plain",
  "subject": "LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches",
  "body": "IceCube Collaboration (http://icecube.wisc.edu/) reports:\n\nSearches for track-like muon neutrino events detected by IceCube consistent with the sky \nlocalization of gravitational-wave candidate S250206dm in a time range of 1000 seconds centered on the alert event time (2025-02-06 21:17:10.436 UTC to 2025-02-06 21:33:50.436 UTC) have been performed [1,2]. 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.  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, such as GW source distance, in the significance estimate [3].\n\nTwo track-like events are found in spatial and temporal coincidence with the gravitational-wave \ncandidate S250206dm calculated from the map circulated in the 3-Initial notice. This\nrepresents an overall p-value of 0.008 from the generic transient search and an overall p-value of 0.011 for the Bayesian search.  These p-values measure the consistency of the observed track-like events with the known atmospheric backgrounds for this single map (not trials corrected for multiple GW events). The most probable multi-messenger source direction based on the neutrinos and GW skymap is RA 149.15 degrees, Dec -17.90 degrees. \n\nThe two 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. The false alarm rate of these coincidences can be obtained by multiplying the p-values with their corresponding GW trigger rates. Further details are available at https://gcn.nasa.gov/missions/icecube.\n\nProperties of the coincident events are shown below. We encourage follow-up observations of both locations.\n\n dt(s)     RA(deg)    Dec(deg)    Angular uncertainty(deg)  p-value(generic transient) p-value(Bayesian)\n-----------------------------------------------------------------------------------------------------\n 289.12\t 149.16\t\t -17.94\t\t 0.43\t\t0.008\t\t\t0.032\n-109.85\t 354.59\t \t 32.79 \t \t 1.42 \t \t0.222\t \t \t0.018\n\nwhere:\ndt = Time of track event minus time of GW trigger (sec)\nAngular uncertainty = Angular uncertainty of track event: the radius of a circle \n     representing 90% CL containment by area.\np-value = the p-value for this specific track event from each search.\n\nThe 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.\n\n[1] M. G. Aartsen et al 2020 ApJL 898 L10\n[2] Abbasi et al. Astrophys.J. 944 (2023) 1, 80\n[3] I. Bartos et al. 2019 Phys. Rev. D 100, 083017",
  "submitter": "Jessie Thwaites at IceCube/U Wisc-Madison <thwaites@wisc.edu>"
}