IceCube-220205B

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

On 2022-02-05 at 20:08:10 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_GOLD alert stream.  The average astrophysical neutrino purity Gold alerts is 50%. This alert has an estimated false alarm rate of 0.734 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection.

Due to a technical issue, the automated GCN notice for this event could not be circulated. The initial position was reconstructed by the IceCube online system and the best-fit parameters are listed below:

Date: 2022-02-05
Time:  20:08:10.59 UT
RA: 266.80 deg (J2000)
Dec: -3.58 deg (J2000)
Error radius: 0.51 deg (90%)

Initial signal probability: 59.5%
Initial neutrino energy: 215.9 TeV

Attempts to use a more sophisticated algorithm that provides refined position and error estimates encountered issues, so further studies will have to be performed before an update is available. Given the topology of the light deposition in the detector, we estimate that the initial direction listed above still provides a good characterization of the event.
 
We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino.

Several gamma-ray sources listed in the 4FGL Fermi-LAT catalog are located near the best-fit neutrino candidate position, 3 of them within a 1 degree radius. These sources are: 4FGL J1747.8-0316 (0.34 deg away), 4FGL J1744.2-0353 (0.81 deg, associated with the source PKS 1741-03) and 4FGL J1749.8-0303 (0.84 deg). 

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

Alexis Coleiro (APC/Universite de Paris) and Damien Dornic (CPPM/CNRS) on behalf of the ANTARES Collaboration.

Using data from the ANTARES detector, we have performed a follow-up analysis of the recently reported track event IceCube-220205B (GCN#31554
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  <https://gcn.gsfc.nasa.gov/gcn3/31554.gcn3
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 >). At the time of the alert, the reconstructed origin was -50.7 degrees below the horizon for ANTARES.

No up-going muon neutrino candidate events were recorded within the 90% error box of the IceCube event during a +/- 1h time-window centered on the IceCube event time, and over which the potential source remained visible all the time. This leads to 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 3 TeV ��� 3.3 PeV (the range corresponding to 5-95% of the detectable flux) for an E^-2 power-law spectrum, and 30 GeV.cm^-2 (0.6 TeV  - 300TeV) for an E^-2.5 spectrum.

A search over an extended time window of +/- 1 day has also yielded no detection (51% visibility). 

ANTARES <http://antares.in2p3.fr/> is the largest undersea neutrino detector (Mediterranean Sea) and it is primarily sensitive to astrophysical neutrinos in the TeV-PeV energy range. At 10 TeV, the median angular resolution for muon neutrinos is about 0.5 degrees. In the range 1-100 TeV ANTARES has a competitive sensitivity to this position in the sky.

S. Garrappa (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg) and J. 
Sinapius (DESY-Zeuthen) on behalf of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the high-energy 
IC220205B neutrino event (GCN 31554
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 ) with all-sky survey data from the 
Large Area Telescope (LAT), on board the Fermi Gamma-ray Space 
Telescope. The IceCube event was detected on 2022-02-05 20:08:10.59 UTC 
(T0) with J2000 position RA = 266.80 (+/- 0.51) deg, Decl. = -3.58 
(+/-0.51) deg 90% PSF containment. One cataloged >100 MeV gamma-ray 
source is located within the 90% IC211216B localization error. This is 
4FGL J1747.8-0316, located 0.34 deg from the neutrino best-fit position�� 
(The Fourth Fermi-LAT catalog DR3; The Fermi-LAT collaboration 2022, 
arXiv:2201.11184
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 ). Based on a preliminary analysis of the LAT data over 
a 1-month and 1-day integration time before T0, this object is not 
significantly detected at gamma rays.

We searched for the existence of intermediate (months to years) 
timescale emission from a new gamma-ray transient source. Preliminary 
analysis indicates no significant (>5sigma) new excess emission (0.1 - 
300 GeV) within the IC220205B 90% confidence localization. Assuming a 
power-law spectrum (photon index = 2.0 fixed) for a point source at the 
IceCube best-fit position, the >100 MeV flux upper limit (95% 
confidence) is < 3.3-10 ph cm^-2 s^-1 for ~13-years (2008-08-04 / 
2022-02-05 UTC), < 2.8e-8 (< 9e-8) ph cm^-2 s^-1 for a 1-month (1-day) 
integration time before T0.

Since Fermi normally operates in an all-sky scanning mode, regular 
monitoring of this source will continue. For these observations the 
Fermi-LAT contact persons are S. Garrappa (simone.garrappa at desy.de) 
and S. Buson (sara.buson at uni-wuerzburg.de).

The Fermi LAT is a pair conversion telescope designed to cover the 
energy band from 20 MeV to greater than 300 GeV. It is the product of an 
international collaboration between NASA and DOE in the U.S. and many 
scientific institutions across France, Italy, Japan and Sweden.

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

IceCube has performed a search for additional track-like muon neutrino events arriving
from the direction of IceCube-220205B (https://gcn.gsfc.nasa.gov/gcn3/31554.gcn3
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 ) in a time
range of 1000 seconds centered on the alert event time (2022-02-05 19:59:50.59 UTC to 2022-02-05 20:16:30.59 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero additional track-like events are found in spatial coincidence with the 90% containment region of IceCube-220205B. We accordingly derive a time-integrated muon-neutrino flux upper limit at the alert position of E^2 dN/dE = 3.1 x 10^-5 TeV cm^-2 at 90% CL, under the assumption of an E^-2 power law. 90% of events IceCube would detect from a source at this declination with an E^-2 spectrum have energies in the approximate energy range between 2 TeV and 7 PeV.

A subsequent search was performed including 2 days of data centered on the alert event time (2022-02-04 20:08:10.59 UTC to 2022-02-06 20:08:10.59 UTC). In this case, we report a p-value of 0.03, consistent with no significant excess of track-like events, and a corresponding time-integrated muon-neutrino flux upper limit assuming an E^-2 spectrum (E^2 dN/dE) of
4.2 x 10^-5 TeV cm^-2 at the 90% CL.

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<mailto:roc@icecube.wisc.edu>.