IceCube-221224A

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-221224A (https://gcn.gsfc.nasa.gov/gcn3/33097.gcn3
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 ) in a time range of 1000 seconds centered on the alert event time (2022-12-24 00:46:49.291 UTC to 2022-12-24 01:03:29.291 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-221224A. 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-221224A 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 3e+02 GeV and 2e+05 GeV.

A subsequent search was performed including 2 days of data centered on the alert event time (2022-12-23 00:55:09.291 UTC to 2022-12-25 00:55:09.291 UTC). In this case, we report a p-value of 0.02, 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-221224A 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<mailto:roc@icecube.wisc.edu>.

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

S. Garrappa (Ruhr-Universitaet Bochum), 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 IC221224A 
high-energy neutrino event (GCN 33097
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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 2022-12-24 at 00:55:09.3 UT 
(T0) with J2000 position RA = 335.74 (+1.01, -0.72) deg, Decl. = +1.42 
(+0.41, -0.30) deg (90% PSF containment). No cataloged gamma-ray (>100 
MeV; The Fermi-LAT collaboration 2022, ApJS, 260, 53) sources are 
located within the 90% IC221224A 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 IC221224A 
best-fit position. Assuming a power-law spectrum (photon index = 2.0 
fixed) for a point source at the IC221224A best-fit position, the >100 
MeV flux upper limit (95% confidence) is < 5.8e-10 ph cm^-2 s^-1 for 
~14-years (2008-08-04 to 2022-12-24 UTC), and < 7.1e-9 (<6.5e-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 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.

D. R. Xiong, J. M. Bai, Y. F. Fan, K. Ye, C. J. Wang, Y. X. Xin, B. L. Lun, J. R. Mao, X. H. Zhao, L. Xu, X. G. Yu, K. X. Lu, X. Ding, D. Q. Wang (Yunnan Observatories), A. J. Castro-Tirado, E. Fernandez-Garcia, Y. D. Hu (IAA-CSIC) and C. J. Perez del Pulgar (UMA) on behalf of the BOOTES team report:

On 22-12-24 at 00:55:09.3 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The nearest gamma-ray source 4FGL J2223.3+0102 is 0.39 deg away from the best-fit event position, but without localization of 90% uncertainty region of the event (GCN 33097
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 ).

We observed the best-fit position of IceCube-221224A and the gamma-ray source 4FGL J2223.3+0102 with BOOTES-4/MET 0.6m automatic optical telescope. We did not detect any optical source within localizations of both them. The upper limits of magnitudes (without being corrected for Galactic extinction) are given as follows. 

Name | UT (start) | Upper Limits (3-sigma) | Exposure Time | Filter 

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Best-fit position ofIceCube-221224A | 22-12-24T11:36:39.25 | 18.90 (0.05) | 5*60s | Clear 

4FGL J2223.3+0102| 2022-11-24T12:06:12.63 | 18.20 (0.04) | 10*60s | SDSS-i  

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The Burst Optical Observer and Transient Exploring System (BOOTES) is a world-wide automatic telescope network which aims to repaid follow-up of transient and astrophysical sources in the sky for which the first station was installed in 1998 (Hu et al. 2021). The fourth station of the BOOTES Network, BOOTES-4/MET, is located at the Lijiang Observatory of the Yunnan Observatories of China (Xiong et al. 2020). We acknowledge the support of these staffs from the BOOTES telescope networks.

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

On 2022-12-24 at 00:55:09.3 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 4.116 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/137469_77414913.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2022-12-24
Time:  00:55:09.3 UT
RA: 335.74 (+1.01, -0.72 deg  90% PSF containment) J2000
Dec: 1.42 (+0.41, -0.30 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 of the event. The nearest gamma-ray source in either catalog is 4FGL J2223.3+0102 at RA: 335.85 deg, Dec: 1.05 deg J2000 (0.39 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