IceCube-170321A

D. Dornic (CPPM/CNRS), A. Coleiro (APC/Universite Paris Diderot) on behalf of the ANTARES Collaboration:

Using data from the ANTARES detector, we have performed a follow-up analysis of the recently reported single high-energy (HESE) neutrino IceCube-170321A (AMON IceCube EHE 80305071 129307). The reconstructed origin was 57 degrees below the horizon for ANTARES, with this position remaining below the horizon from -9h, +5h around the time of the alert. Thus ANTARES had a high sensitivity to any neutrinos from the same region.

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. A search on an extended time window of +/- 1 day has also yielded no detection (58% visibility probability).

This yields a preliminary 90% confidence level upper limit on the muon-neutrino fluence from a point source of 16 GeV.cm^-2 over the energy range 2.5 TeV-2.5 PeV (the range corresponding to 5-95% of the detectable flux) for an E^-2 power-law spectrum, and 26 GeV.cm^-2 (510 GeV-220 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.

Erik Blaufuss (University of Maryland) reports on behalf of the IceCube 
Collaboration (http://icecube.wisc.edu/).

On 21 March, 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  Extremely High Energy (EHE) track event selection.   
The IceCube detector was in a normal operating state. EHE events 
typically have a neutrino interaction vertex that is outside the 
detector, produce a muon that traverses the detector volume, and have a 
high light level (a proxy for energy).

After the initial automated alert 
(https://gcn.gsfc.nasa.gov/notices_amon/80305071_129307.amon), more 
sophisticated reconstruction algorithms have been applied offline, with 
the direction refined to:

Date: 2017-03-21
Time: 07:32:20.69 UT
RA: 98.30  (+/- 1.2  deg  90% PSF containment) J2000
Dec:  -15.02(+/- 1.2 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.

This event was found to be close to  the edge of the instrumented 
detector volume, which has
increased the overall direction uncertainty for this event.

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

C. M. Hui (MSFC), A. Goldstein (USRA), E. Burns (UAH), 
and P. Jenke (UAH) report on behalf of the Fermi GBM team:

We have searched the Fermi Gamma-ray Burst Monitor data for a
gamma-ray counterpart to IceCube-170321A 
(Blaufuss 2017, GCN 20929
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 ).
The position was occulted by the Earth for Fermi at the time 
the neutrino was detected. GBM therefore cannot set any limits 
on impulsive emission.

Measurements using the Earth Occultation technique around this position
place a three sigma flux upper limit of about 230 mCrab between 12 and
100 keV between Mar 18th and Mar 21st.

V. Savchenko (ISDC, University of Geneva, CH),
M. Santander (Barnard College, Columbia University, US),
A. Keivani (Dept. of Physics, Penn State University, US),
E. Gotthelf (Columbia University, US),
C. Ferrigno (ISDC, University of Geneva, CH),
P. Ubertini, A. Bazzano, L. Natalucci (INAF IAPS-Roma, Italy),
S. Mereghetti (INAF IASF-Milano, Italy),
P. Laurent (CEA, Saclay, France), E. Kuulkers (ESTEC/ESA, The Netherlands)


On 2017-03-21 07:32:20.69 the IceCube detector has observed a
high-energy neutrino likely of astrophysical origin, IceCube-170321A
(GCN 20929
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 ). The location of the event is contained in a circle of
1.2 degree radius (90% confidence) centered at RA=98.30 Dec=-15.02..

INTEGRAL has performed a Target-of-Opportunity observation of the
neutrino localization region, starting 31.5 hours after the neutrino
detection from 2017-03-22 15:10:29 UTC to 2017-03-23 04:30:20 UTC,
corresponding to a total on-target time of 45 ks. IBIS was online for
a fraction of this time, 39.5ks.

We have investigated the data collected by INTEGRAL IBIS and JEM-X
without finding any significant new source in the JEM-X data between 3
and 35 keV within the localization area of IceCube-170321A. In the
IBIS/ISGRI 25-80 keV mosaic image, corresponding to the whole
observation period, we identify an excess with a SNR of 3.9. The
probability of this excess happening randomly in the region of
interest is 3%.

We derived an upper limit on the flux of any new source in the 90%
localization region of IceCube-170321A, averaged over the observation,
of 4 mCrab (1.2x10-10 erg/cm2/s) in 3-35 keV, 3.7 mCrab (3.7x10-11
erg/cm2/s) in 25-80 keV , and 7 mCrab (1.0x10-10 erg/cm2/s) in 80-200
keV.

We have also searched for new sources in the whole area covered by the
observation with sensitivity not substantially worse than the deepest
target sensitivity: 16 degree diameter for JEM-X (3-35 keV) and 30
degrees for ISGRI (20-200 keV). We did not find any unidentified
source with a SNR larger than 5.

INTEGRAL/SPI-ACS observations at the time of the neutrino detection is
reported in GCN 20928
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 .

We thank the INTEGRAL Science Operations Centre (ESA/ESAC, Madrid,
Spain) and the Mission Operations Centre (ESA/ESOC, Darmstadt,
Germany) for their prompt scheduling of these observations.

A. Keivani (PSU), D. B. Fox (PSU), P.A. Evans (U. Leicester), J.A.
Kennea (PSU), G. Tesic (PSU), D.F. Cowen (PSU), and J.P. Osborne (U.
Leicester) report on behalf of the Swift-IceCube collaboration:


Swift has observed the field of the IceCube EHE neutrino,
IceCube-170321A (https://gcn.gsfc.nasa.gov/gcn3/20929.gcn3
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 ), utilizing
the on-board 7-point tiling pattern to cover a region centered on the
initial automated alert position RA,Dec (J2000) = (98.3268, -14.4861),
with a radius of approximately 0.55 degrees. This covers about 21% of
the 90% error region of the refined IceCube localization.

Swift-XRT collected ~880 s per field of PC mode data per tile. The
observations were taken between 14:09:02 on 2017-03-21 and 18:03:00 on
2017-03-21 (i.e. from 23.7 ks to 37.8 ks after the neutrino trigger),
and covered 0.77 square degrees.

Analysis using standard Swift tools yields >3-sigma detection of a
single X-ray source, 1SXPS J063214.5-143300, which is also seen in
previous observations of the field by Swift XRT, in a similar flux and
spectral state. As such we conclude that there are no candidate X-ray
counterparts to the possibly-cosmic high-energy neutrino within the
covered region. Our 3-sigma upper limit on the count rate of any such
counterpart is 3.6e-3 XRT ct s-1, which corresponds to a 0.3-10 keV
flux of 1.48e-13 erg cm-2 s-1 for a typical afterglow/AGN power-law
spectrum with photon index gamma=1.7 and equivalent hydrogen column
density N_H=3e+20 cm-2.

Details of the detected X-ray source are below.

Source 1
========
RA:          06h 32m 14.5s = 98.06042d 	
Dec:         -14d 32' 59.9" = -14.55000d
Error:       6.0 arcsec (90% confidence radius)
Count rate:  (2.2 +/- 0.6) x 10^-2 ct s^-1
Flux:        (9.0 +/- 2.5) x 10^-13 erg cm^-2 s^-1     Notes:
This source has been previously detected by Swift (1SXPS
J063214.5-143300) and the observed flux is consistent with the
catalogued value.

D. Svinkin, S. Golenetskii, R.Aptekar, D. Frederiks, P. Oleynik,
M. Ulanov, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline,
on behalf of the Konus-Wind team, report:

Using Konus-Wind (KW) waiting mode data, we have performed a search for
a gamma-ray transient around the time of the cosmic neutrino candidate 
IceCube-170321A (2017-03-21 07:32:20.69 UT, hereafter T0; Blaufuss, GCN 
20929
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 ).

In the interval T0 +/- 1000 s we estimate an upper limit (90% conf.) on 
the 10 keV ��� 10 MeV fluence to ~6.6x10^-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 ~2.3x10^-7 
erg/cm^2/s (10 keV - 10 MeV, 2.944 s scale).

All the quoted values are preliminary.