IceCube-220424A
GCN Circular 31942
Subject
IceCube-220424A - IceCube observation of a high-energy neutrino candidate track-like event
Date
2022-04-24T01:53:08Z (3 years ago)
From
Marcos Santander at U. Alabama/IceCube <jmsantander@ua.edu>
The IceCube Collaboration (http://icecube.wisc.edu/) reports:
On 2022-04-24 at 01:06:24.06 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 1.205 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/136565_2186969.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:
Date: 2022-04-24
Time: 01:06:24.06 UT
RA: 346.11 (+1.26, -1.33 deg 90% PSF containment) J2000
Dec: 8.91 (+0.95, -1.01 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.
One gamma-ray source listed in the 4FGL-DR3 Fermi-LAT catalog is located within the 90% uncertainty region for the event: the source 4FGL J2306.6+0940 (346.65 deg, 9.67 deg J2000), 0.93 deg away from the best-fit neutrino candidate 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
GCN Circular 31947
Subject
Fermi-LAT Gamma-ray Observations of IceCube-220424A
Date
2022-04-25T07:55:40Z (3 years ago)
From
Sara Buson at GSFC/Fermi <sara.buson@gmail.com>
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 IC220424A neutrino event (GCN 31942) 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 2022-04-24 at 01:06:24.06 UT (T0) with J2000 position RA = 346.11 (+1.26, -1.33) deg, Decl. = +8.91 (+0.95, -1.01) deg (90% PSF containment). One cataloged gamma-ray (>100 MeV) source is located within the 90% IC220424A localization region (4FGL-DR3; arXiv:2201.11184; The Fermi-LAT collaboration 2020, ApJS, 247, 33). This is the unassociated gamma-ray source 4FGL J2306.6+0940.
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 IC220424A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC220424A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 1.5e-10 ph cm^-2 s^-1 for ~13-years (2008-08-04 to 2022-04-24 UTC), and < 5.1e-9 (< 4.1e-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 source will continue. For these observations the Fermi-LAT contact persons are S. Garrappa (simone.garrappa at desy.de <http://desy.de/>) and S. Buson (sara.buson at uni-wuerzburg.de <http://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.
GCN Circular 31970
Subject
IceCube-220424A: Upper limits from a search for additional neutrino events in IceCube
Date
2022-04-29T16:21:57Z (3 years ago)
From
Jessie Thwaites at IceCube/U Wisc-Madison <thwaites@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-220424A (https://gcn.gsfc.nasa.gov/gcn3/31942.gcn3) in a time range of 1000 seconds centered on the alert event time (2022-04-24 00:58:04.060 UTC to 2022-04-24 01:14:44.060 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-220424A. 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-220424A 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 3e+02 GeV and 1e+05 GeV.
A subsequent search was performed including 2 days of data centered on the alert event time (2022-04-23 01:06:24.060 UTC to 2022-04-25 01:06:24.060 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-220424A is 1.5e-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)