IceCube-221216A

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

On 22-12-16 at 06:00:14.01 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 1.59 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/137390_43495485.amon), more 
sophisticated reconstruction algorithms have been applied offline, with 
the direction refined to:

Date: 22-12-16
Time: 06:00:14.01 UT

RA: 6.86 (+1.08/-2.06 deg  90% PSF containment) J2000
Dec: +10.43 (+1.54/-1.07 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 
J0023.4+0920 at RA 5.85, dec +9.35 J2000, located 1.47 deg away from the 
best fit 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-221216A (https://gcn.gsfc.nasa.gov/gcn/gcn3/33065.gcn3
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 ) in a time range of 1000 seconds centered on the alert event time (2022-12-16 05:51:54.010 UTC to 2022-12-16 06:08:34.010 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-221216A. 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-221216A is 1.3e-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 1e+05 GeV.


A subsequent search was performed including 2 days of data centered on the alert event time (2022-12-15 06:00:14.010 UTC to 2022-12-17 06:00:14.010 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-221216A ranges from 1.5e-01 to 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)

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 IC221216A 
high-energy neutrino event (GCN 33065
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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 2022-12-16 at 06:00:14.01 
UT (T0) with J2000 position RA = 6.86 (+1.08, -2.06) deg, Decl. = +10.43 
(+1.54, -1.07) deg (90% PSF containment). No cataloged gamma-ray (>100 
MeV) source is located within the 90% IC221216A localization region 
(4FGL-DR3; The Fermi-LAT collaboration 2022, ApJS, 260, 53).

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 IC221216A 
best-fit position. Assuming a power-law spectrum (photon index = 2.0 
fixed) for a point source at the IC221216A best-fit position, the >100 
MeV flux upper limit (95% confidence) is < 7.6e-10 ph cm^-2 s^-1 for 
~14-years (2008-08-04 to 2022-12-16 UTC), and < 1.3e-8 (<7.8e-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.

Sven Weimann (Ruhr University Bochum), Simeon Reusch, Jannis Necker (DESY), Robert Stein (Caltech) and Anna Franckowiak (DESY/Ruhr University Bochum) report:

On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations:

As part of the ZTF neutrino follow up program (Stein et al. 2022), we observed the localization region of the neutrino event IceCube-221216A (Santander et al., GCN 32037
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 ) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the g- and r-band beginning at 2022-12-17 04:57 UTC, approximately 23.0 hours after event time. We covered 75.5% (5.4 sq deg) of the reported localization region. This estimate accounts for chip gaps. Each exposure was 300s with a typical depth of 21.0 mag.
 
The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alert database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019).

Two transient detections remained after the automated cuts, but were ruled out as candidate counterparts by visual inspection. We will continue monitoring the localization region with ZTF in the g-band for the next week.

ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA; WIS, Israel; OKC, Sweden; JSI/UMd, USA; DESY, Germany; TANGO, Taiwan; UW Milwaukee, USA; LANL, USA; TCD, Ireland; IN2P3, France.

GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949.
Alert distribution service provided by DIRAC@UW (Patterson et al. 2019).
Alert database searches are done by AMPEL (Nordin et al. 2019).
Alert filtering is performed with nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf).