IceCube-220629A

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

On 2022-06-29 at 23:51:31.69 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 3.638 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/136783_66879340.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2022-06-29
Time:  23:51:31.69 UT
RA: 163.92 (+0.80, -0.67 deg  90% PSF containment) J2000
Dec: 4.33 (+0.51, -0.34 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.  We recognize the alert best-fit position falls within the 90% uncertainty region of the recent high-energy neutrino candidate IceCube-220627A (GCN #32277
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 ), but given the spatial extent of the error region for the previous alert we remain uncertain as to potential coincidences.

There are no Fermi 4FGL or 3FHL catalog sources in the 90% uncertainty region of the event. The nearest source in either catalog is 4FGL J1050.1+0432 (RA: 162.55 deg, Dec: 4.54 deg J2000, 1.39 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

Woo-Hyeon Heo, Hugo Ayala (UOS, PSU) reports on behalf of the HAWC
collaboration (http://www.hawc-observatory.org/collaboration):

On 2022/06/29 23:51:32 UTC, the IceCube collaboration reported a
track-like very-high-energy event  that has a high probability of
being an astrophysical neutrino, IceCube-220629A. Location is at
RA: 163.92 (+0.80/-0.67 deg  90% PSF containment) J2000
Dec: 4.33 (+0.51/-0.34 deg 90% PSF containment) J2000
(GCN circular 32299
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 ).

We performed two types of analyses for the follow-up. The first is for
a steady source in archival data and the second is a search for a
transient source. We assume a power-law spectrum with an index of -2.3
for both analyses.

Search for a steady source in archival data:
The archival data spans from November 2014 to June 2019. We searched
inside the reported IceCube error region.
The most significant location, with p-value 3.91e-03 (2.46e-02
post-trials),
is at RA 163.26 deg, Dec +4.48 deg (��0.14 deg 68% containment) J2000.
We set a time-integrated 95% CL  upper limit on gamma rays at the
maximum position of:

E^2 dN/dE = 3.15e-13 (E/TeV)^-0.3 TeV.cm^-2.s^-1

Search for a transient source.

Since the event was not in our field of view at the time reported,
we report the combined result for the transits before and after the
IceCube event.

Data acquisition started on 2022/06/29 01:36:29 UTC and ended
2022/06/30 04:28:44 UTC.
The most significant location, with p-value 3.30e-01 (9.22e-01 post-trials),
is at RA 163.92 deg, Dec +4.82 deg (��4.15 deg 68% containment) J2000.
We set a time-integrated 95% CL upper limit at the position of
maximum significance of:

E^2 dN/dE = 1.10e-11 (E/TeV)^-0.3 TeV.cm^-2.s^-1

HAWC is a very-high-energy gamma-ray observatory operating in Central
Mexico at latitude 19 deg. north. Operating day and night with over
95% duty cycle, HAWC has an instantaneous field of view of 2 sr and
surveys 2/3 of the sky every day. It is sensitive to gamma rays from
300 GeV to 100 TeV.

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

We report an analysis of observations of the vicinity of the high-energy 
IC220629A neutrino event (GCN 32299
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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 2022-06-29 at 23:51:31.69�� 
UT (T0) with J2000 position RA = +163.92 (+0.80, -0.67) deg, Decl. = 
4.33 (+0.51, -0.34) deg (90% PSF containment). No cataloged gamma-ray 
(>100 MeV) sources are located within the 90% IC220629A localization 
region (4FGL-DR3; arXiv:2201.11184
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 ; The Fermi-LAT collaboration 2020, 
ApJS, 247, 33).

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 IC220629A 
best-fit position. Assuming a power-law spectrum (photon index = 2.0 
fixed) for a point source at the IC220629A best-fit position, the >100 
MeV flux upper limit (95% confidence) is < 6.5e-10 ph cm^-2 s^-1 for 
~14-years (2008-08-04 to 2022-06-29 UTC), and < 7.5e-9 (< 3.4e-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 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-220629A (https://gcn.gsfc.nasa.gov/gcn3/32299.gcn3
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  ) in a time range of 1000 seconds centered on the alert event time (2022-06-29 23:43:11.690 UTC to 2022-06-29 23:59:51.690 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-220629A. 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-220629A 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 1e+05 GeV.


A subsequent search was performed including 2 days of data centered on the alert event time (2022-06-28 23:51:31.690 UTC to 2022-06-30 23:51:31.690 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-220629A 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)