IceCube-230306A

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

On 2023-03-06 at 10:59:30.41 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 for Gold alerts is 50%. This alert has an 
estimated false alarm rate of 0.71 events per year due to atmospheric 
backgrounds. The IceCube detector was in a normal operating state at the 
time of detection.

After the initial automated alert 
(https://gcn.gsfc.nasa.gov/notices_amon_g_b/137711_79205800.amon), more 
sophisticated reconstruction algorithms have been applied offline, with 
the direction refined to:

Date: 2023-03-06
Time: 10:59:30.41 UT
RA: 72.86 (+0.87/-0.89 deg  90% PSF containment) J2000
Dec: +34.23 (+0.87/-0.86 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.

There are no Fermi 4FGL or 3FHL catalog sources in the 90% uncertainty 
region. The nearest gamma-ray source in either catalog is 4FGL 
J0444.6+3425 at RA: 71.16 deg, Dec: 34.42 deg (1.42 deg away from the 
best-fit event position).

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

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

We report an analysis of observations of the vicinity of the IC230306A  high-energy neutrino event (GCN 33403
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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 2023-03-06 at 10:59:30.41 UT (T0) with J2000 position RA = 72.86 (+0.87, -0.89) deg, Decl. = +34.23 (+0.87, -0.86) deg (90% PSF containment).  No cataloged gamma-ray (>100 MeV; The Fermi-LAT collaboration 2022, ApJS, 260, 53) sources are located within the 90% IC230306A  localization region.

We searched for intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (> 5 sigma) new excess emission (> 100 MeV) at the IC230306A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC230306A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 4.8e-10 ph cm^-2 s^-1 for ~14-years (2008-08-04 to 2023-03-06 UTC), and < 8.8e-9 (<1.8e-7) 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 region will continue. For these observations the Fermi-LAT contact persons are S. Garrappa (simone.garrappa at ruhr-uni-bochum.de), J. Sinapius (jonas.sinapius 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 [1] for additional track-like muon neutrino events arriving from the direction of IceCube-230306A (https://gcn.gsfc.nasa.gov/gcn3/33403.gcn3
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 ) in a time range of 1000 seconds centered on the alert event time (2023-03-06 10:51:10.410 UTC to 2023-03-06 11:07:50.410 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-230306A. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-230306A is 1.4e-01 GeV cm^-2 in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 2e+02 GeV and 6e+04 GeV.


A subsequent search was performed including 2 days of data centered on the alert event time (2023-03-05 10:59:30.410 UTC to 2023-03-07 10:59:30.410 UTC). In this case, we report a p-value of 1.00, consistent with no significant excess of track events. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-230306A is 1.6e-01 GeV cm^-2 in a 2 day time window.


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.


[1] IceCube Collaboration, R. Abbasi  et al., ApJ 910 4 (2021)