IceCube-250101A

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

On 2025-01-01 at 21:04:57.73 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_Bronze alert stream. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 1.9213 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/140312_53817657.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2025-01-01
Time: 21:04:57.73 UT
RA: 318.96 (+0.64, -0.63 deg 90% PSF containment) J2000
Dec: -0.93 (+0.49, -0.44 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 is one Fermi 4FGL-DR4 or 3FHL catalog source in the 90% uncertainty region: 4FGL J2115.9-0113 at RA: 319.00 deg, Dec: -1.23 deg J2000 (0.3 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

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-250101A (https://gcn.nasa.gov/circulars/38770
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 ) in a time range of 1000 seconds centered on the alert event time (2025-01-01 20:56:37.730 UTC to 2025-01-01 21:13:17.730 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-250101A. 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-250101A is 1.5e-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 3e+02 GeV and 2e+05 GeV. 

A subsequent search was performed including 2 days of data centered on the alert event time (2024-12-31 21:04:57.730 UTC to 2025-01-02 21:04:57.730 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-250101A 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)

C. Bartolini (Università di Trento & INFN Bari), S. Garrappa (Weizmann Institute of Science), L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and J. Sinapius (DESY) and P. M. Veres (Ruhr University Bochum) on behalf of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the high-energy IC250101A neutrino event (GCN 38770
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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 2025-01-01 21:13:17.730 UTC (T0) with J2000 position RA = 318.96 (+0.64, -0.63) deg, Decl. = -0.93 (+0.49, -0.44) deg 90% PSF containment. One cataloged >100 MeV gamma-ray source is located within the 90% IC-250101A localization error, at a distance of roughly 0.3 deg (Fourth Fermi-LAT catalog, 4FGL-DR4, The Fermi-LAT collaboration 2023, arXiv:2307.12546
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 ). This is the object 4FGL J2115.9-0113. Based on a preliminary analysis of the LAT data over the timescale of one month prior T0, this object is not significantly detected at gamma-rays.

We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC250101A 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 <2.0e-09 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), <1.1e-09 ph cm^-2 s^-1 for a 1-month integration time before T0.

Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this source, the Fermi-LAT contact person is C. Bartolini (chiara.bartolini at ba.infn.it). 

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.