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GCN Circular 21508

Subject
LIGO/Virgo G298048: FOUND COINCIDENT IceCube neutrino observation
Date
2017-08-17T14:05:11Z (7 years ago)
From
Stefan Countryman at LIGO Scientific Collaboration <stefan.countryman@ligo.org>
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

The analysis FOUND A COINCIDENT ONLINE TRACK-LIKE NEUTRINO CANDIDATE detected by IceCube within the 500 second window surrounding G298048 within the BAYESTAR skymap. The coordinates of the reconstructed neutrino source are below:

#            dt[s]     RA[deg]    Dec[deg]      E[TeV]  Sigma[deg]
------------------------------------------------------------------
1.         -166.00       291.4        69.0        0.37         3.1

We searched IceCube online track-like neutrino candidates (GFU) detected in a [-500,500] second interval about the LIGO-Virgo trigger G298048. We compared the candidate source directions of 6 temporally-coincident neutrinos to the BAYESTAR skymap, with the following parameters:

#            dt[s]     RA[deg]    Dec[deg]      E[TeV]  Sigma[deg]
------------------------------------------------------------------
1.         -419.79       226.7        12.0        0.65         1.8
2.         -266.61       239.6        19.6        1.04         1.6
3.         -165.72       291.3        68.8        0.37         3.1
4.         -153.47       182.0        -3.2        0.88         0.9
5.          310.59         1.4        23.8        0.50         1.5
6.          390.94       203.2         6.0        1.00         0.7


(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])

A coincident neutrino-GW skymap has been posted to GraceDB (<https://gracedb.ligo.org/apiweb/events/G298048/files/coinc_skymap_initial_icecube.png,0>). A JSON-formatted list of the above neutrinos can be downloaded from GraceDB at: <https://gracedb.ligo.org/apiweb/events/G298048/files/IceCubeNeutrinoList.json,0>

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 <http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1610.01814>; for more information on joint neutrino and gravitational wave searches, please refer to <http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1602.05411>.
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