IceCube-171015A

The IceCube Collaboration (http://icecube.wisc.edu/) reports:

On 15 October, 2017 IceCube detected a track-like, very-high-energy 
event with a high probability of being of astrophysical origin. The 
event was identified by the High Energy Starting Event (HESE) selection. 
The IceCube detector was in a normal operating state. HESE events have a 
neutrino vertex inside of the detector (to reduce background) and have a 
high light level (a proxy for energy).

After the initial automated alert 
(https://gcn.gsfc.nasa.gov/notices_amon/56068624_130126.amon), more 
sophisticated reconstruction algorithms have been applied offline, with 
the direction refined to:

Date: 2017-10-15
Time: 01:34:30.06 UT
RA: 162.86 deg (-1.70 deg / +2.60 deg 90% PSF containment) J2000
Dec: -15.44 deg (-2.00 deg / +1.60 deg 90% PSF containment) J2000

We encourage follow-up by ground and space-based instruments to help 
identify a possible astrophysical source for the candidate neutrino.

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

V. Savchenko, C. Ferrigno (ISDC, University of Geneva, CH)
P. Ubertini, A. Bazzano, L. Natalucci. J. Rodi (INAF IAPS-Roma, Italy)
S. Mereghetti (INAF IASF-Milano, Italy)
P. Laurent (CEA, Saclay, France)
E. Kuulkers (ESAC/ESA, Madrid, Spain)

Using INTEGRAL SPI-ACS we have performed a search for a prompt
gamma-ray counterpart of the cosmic neutrino candidate IceCube-171015A
(GCN 22016
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 ).

At the time of the event (2017-10-15 01:34:30 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The neutrino localization was
at an angle of 85 deg with respect to the spacecraft pointing axis.
This orientation implies near-optimal response of SPI-ACS, and this
instrument provides best sensitivity to both short and long GRBs.

The background within +/-300 seconds around the event was very stable.
We do not detect any significant counterparts and estimate a 3-sigma
upper limit on the 75-2000 keV fluence of 2.2x10^-7 erg/cm^2 for a
burst lasting less than 1 s with a characteristic short GRB spectrum
(an exponentially cut off power law with alpha=-0.5 and Ep=600 keV)
occurring at any time in the interval within 300 s around T0.

For a typical long GRB spectrum (Band function with alpha=-1,
beta=-2.5, and Ep=300 keV), the derived peak flux upper limit is
~1.9x10^-7 (6.2x10^-7) erg/cm^2/s at 1 s (8 s) time scale in 75-2000
keV energy range.

Damien Dornic (CPPM / CNRS), Alexis Coleiro (APC / IFIC)  report on behalf of the ANTARES Collaboration:

Using online data from the ANTARES detector, we have performed a follow-up analysis of the recently reported high-energy starting event (HESE) neutrino IceCube-171015 (AMON IceCube HESE 56068624_130126). The reconstructed origin was 24.5 degrees below the horizon for ANTARES.

No up-going muon neutrino candidate events were recorded within three degrees of the IceCube event coordinates during a +/- 1h time-window centered on the IceCube event time (100% visibility probability). A search on an extended time window of +/- 1 day (58% visibility probability) has also yielded no detection.

This yields a preliminary 90% confidence level upper limit on the muon-neutrino fluence from a point source of 14 GeV.cm^-2 over the energy range 2.7 TeV - 2.8 PeV (the range corresponding to 5-95% of the detectable flux) for an E^-2 power-law spectrum, and 27 GeV.cm^-2 (440 GeV - 240 TeV) for an E^-2.5 spectrum.

ANTARES is the largest neutrino detector installed in the Mediterranean Sea, and is primarily sensitive to astrophysical neutrinos in the TeV-PeV energy range.  At 10 TeV, the median angular resolution for muon neutrinos is below 0.5 degrees. In the range 1-100 TeV, ANTARES has the best sensitivity to this position in the sky.

R. Hamburg (UAH) and A. Goldstein (USRA) report on behalf
of the Fermi GBM team:

We have searched the Fermi Gamma-ray Burst Monitor data
for a gamma-ray counterpart to the IceCube neutrino 171015A
(GCN 22016
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 ). The location of the neutrino was observed by
GBM with good geometry.

There were no associated on-board triggers +/- 15 hours of
the neutrino event time. The ground-based untargeted search
of GBM data (Briggs et al., in prep) did not find any candidates
+/- 1 hour of the event time. The targeted search of GBM data
([1],[2]) also searched +/- 30 s around the neutrino event time,
processing timescales of 0.256 s to 8.192 s. No significant
candidates were found.

Using a hard Band function with (Epeak, alpha, beta) =
(500 keV, -0.5,-2.5), we set 3 sigma flux-averaged upper limits
for any transient within 30 s of the neutrino event time.
Averaged over (0.1 s, 1 s, and 10 s) timescales, the
corresponding upper limits in the 10-1000 keV band are
(16.4, 4.82, 1.47) E-7 erg/s/cm^2. Using an exponentially cut-off
power law parametrized with (Epeak, index) = (566 keV, -0.42),
which represents the average GBM-triggered short GRB, the
flux-averaged upper limits are (18.0, 5.26, 1.61) E-7 erg/s/cm^2.


[1] L. Blackburn et al. 2015, ApJS 217, 8
[2] A. Goldstein et al. arXiv:1612.02395
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A. Kozlova, S. Golenetskii, R.Aptekar, D. Frederiks, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline,
on behalf of the Konus-Wind team, report:

Using Konus-Wind (KW) data, we have performed a search for
a gamma-ray transient around the time of the cosmic neutrino
candidate IceCube-171015A (2017-10-15 01:34:30.06 UT,
hereafter T0; Blaufuss, GCN 22016
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 ;
https://gcn.gsfc.nasa.gov/notices_amon/56068624_130126.amon)

No triggered KW event happened from ~3.3 days before and up to ~3.6 days
after T0. The closest waiting-mode event was ~1.9 hours after T0.
Using waiting-mode data within the interval T0  +/- 1000 s,
we found no significant (> 5 sigma) excess over the background
in both KW detectors on temporal scales from 2.944 s to 100 s in the 
80-1000 keV band.

We estimate an upper limit (90% conf.) on the 10 keV ��� 10 MeV fluence
to 8.7x10^-7 erg/cm^2 for a burst lasting less than 2.944 s and having a
typical KW short GRB spectrum (an exponentially cut off power law with
alpha =-0.5 and Ep=500 keV). For a typical long GRB spectrum (the Band
function with alpha=-1, beta=-2.5, and Ep=300 keV), the corresponding
limiting peak flux is 3.1x10^-7 erg/cm^2/s (10 keV - 10 MeV, 2.944 s 
scale).

All the quoted values are preliminary.