# GCN Circular 27043

**Subject**

LIGO/Virgo S200213t: 1 counterpart neutrino candidate from IceCube neutrino searches

**Date**

2020-02-13T04:40:26Z (5 years ago)

**From**

Raamis Hussain at IceCube <raamis.hussain@icecube.wisc.edu>

```
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)
```