GCN Circular 21226
Subject
LIGO/Virgo G288732: IceCube neutrino observations update
Date
2017-06-08T18:46:47Z (8 years ago)
From
Imre Bartos at Columbia/LIGO <imrebartos@gmail.com>
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 previously reported on the online track-like neutrino search for LIGO-Virgo trigger G288732. We are updating this result with adopting a new online configuration, which enables better background rejection online, allowing for an increased rate of events passing the neutrino track event selection, along a higher efficiency for neutrino events. With this online search, the expected background neutrino rate is ~6 within our [-500,500] time window.
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We searched IceCube online track-like neutrino candidates (GFU) detected in a [-500,500] second interval about the LIGO-Virgo trigger G288732. We compared the candidate source directions of 7 temporally-coincident neutrinos to the BAYESTAR skymap, with the following parameters:
# dt[s] RA[deg] Dec[deg] E[TeV] Sigma[deg]
------------------------------------------------------------------
1. -106.97 28.5 23.7 1.03 1.2
2. -97.96 252.1 8.0 0.90 1.8
3. -67.26 299.0 28.6 1.38 1.4
4. -44.07 99.0 -67.8 224.91 0.2
5. 331.13 269.8 43.7 1.09 5.7
6. 337.70 241.7 26.3 0.97 1.5
7. 462.61 310.9 -5.5 2.53 0.8
(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])
The analysis found NO COINCIDENT ONLINE TRACK-LIKE NEUTRINO CANDIDATES detected by IceCube within the 500 second window surrounding G288732 within the BAYESTAR skymap.
A coincident neutrino-GW skymap has been posted to GraceDB (<https://gracedb.ligo.org/apiweb/events/G288732/files/coinc_skymap_initial_icecube.png,2>). A JSON-formatted list of the above neutrinos can be downloaded from GraceDB at:<https://gracedb.ligo.org/apiweb/events/G288732/files/IceCubeNeutrinoList.json,3>
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>.