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GCN Circular 21432

LIGO/Virgo G296853: IceCube neutrino observations
2017-08-09T10:36:33Z (7 years ago)
Stefan Countryman at LIGO Scientific Collaboration <>
I. Bartos, S. Countryman (Columbia), C. Finley (U Stockholm), E. Blaufuss
(U Maryland), R. Corley, Z. Marka, S. Marka (Columbia) on behalf of the
IceCube Collaboration

We searched IceCube online track-like neutrino candidates (GFU) detected in
a [-500,500] second interval about the LIGO-Virgo trigger G296853. We
compared the candidate source directions of 4 temporally-coincident
neutrinos to the BAYESTAR skymap, with the following parameters:

#            dt[s]     RA[deg]    Dec[deg]      E[TeV]  Sigma[deg]
1.         -310.02        65.9        -5.2        1.11         0.5
2.         -128.45        74.0       -29.2       52.68         0.2
3.          361.60       164.0       -14.6       20.50         0.5
4.          438.49       121.1       -64.8       81.83         2.1

(dt--time from GW in [seconds]; RA/Dec--sky location in [degrees];
E--reconstructed secondary muon energy in [TeV]; Sigma--uncertainty of
direction reconstruction in [degrees])

detected by IceCube within the 500 second window surrounding G296853 within
the BAYESTAR skymap.

A coincident neutrino-GW skymap has been posted to GraceDB (<
coinc_skymap_initial_icecube.png,0>). A JSON-formatted list of the above
neutrinos can be downloaded from GraceDB at: <

In addition, we are performing coincident searches with other IceCube data
streams, including the high-energy starting events (HESE) and Supernova
triggers.  HESE events have typical energies > 60 TeV and start inside the
detector volume, leading to a relatively pure event sample with a high
fraction of astrophysical neutrinos.  The SN trigger system is sensitive to
sudden increases in photomultiplier counts across the detector, which could
indicate a burst of MeV neutrinos.  We will submit separate GCN circulars
if coincident HESE or SN triggers are found.

The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector
operating at the geographic South Pole, Antarctica.  For a description of
the IceCube realtime alert system, please refer to <>; for more
information on joint neutrino and gravitational wave searches, please refer
to <>.
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