IceCube-220221A
GCN Circular 31618
Subject
IceCube-220221A - IceCube observation of a high-energy neutrino candidate track-like event
Date
2022-02-21T02:21:22Z (3 years ago)
From
Marcos Santander at U. Alabama/IceCube <jmsantander@ua.edu>
The IceCube Collaboration (http://icecube.wisc.edu/) reports:
On 2022-02-21 at 00:42:19.12 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 0.360 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/136348_65788242.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:
Date: 2022-02-21
Time: 00:42:19.12
RA: 287.84 (+4.00, -3.96 deg 90% PSF containment) J2000
Dec: 20.74 (+4.31, -2.26 deg 90% PSF containment) J2000
The event was produced by a short, bright muon track near the bottom of the detector. This topology resulted in a large shift between the initial and revised muon track positions, and an uncertainty region significantly larger than it is typical for these alerts.
We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino.
Due to the large uncertainty region and the vicinity of the Galactic Plane, there are 6 sources listed in the Fermi-LAT 4FGL-DR2 catalog within the 90% containment region for the event, the closest being 4FGL J1908.9+2103 (associated with PSR J1908+2105, at 0.65 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
GCN Circular 31632
Subject
Fermi-LAT Gamma-ray Observations of IceCube-220221A
Date
2022-02-22T12:48:26Z (3 years ago)
From
Sara Buson at GSFC/Fermi <sara.buson@gmail.com>
S. Buson (Univ. of Wuerzburg), S. Garrappa (DESY-Zeuthen) and J. Sinapius (DESY-Zeuthen) on behalf of the Fermi-LAT collaboration:
We report an analysis of observations of the vicinity of the high-energy IC220221A neutrino event (GCN 31618) 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 2022-02-21 at 00:42:19.12 UT (T0) with J2000 position RA = 287.84 (+4.00, -3.96) deg, Decl. = 20.74 (+4.31, -2.26) deg (90% PSF containment). Several cataloged gamma-ray (>100 MeV) sources are located within the 90% IC220221A localization region (4FGL-DR3; arXiv:2201.11184; 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 IC220221A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC220221A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 1.4e-9 ph cm^-2 s^-1 for ~13-years (2008-08-04 to 2022-02-21 UTC), and < 2.1e-8 (< 9.9e-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. Buson (sara.buson at uni-wuerzburg.de) and S. Garrappa (simone.garrappa at desy.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 31638
Subject
IceCube-220221A: Upper limits from a search for additional neutrino events in IceCube
Date
2022-02-22T20:24:19Z (3 years ago)
From
Alex Pizzuto at ICECUBE/U of Wisconsin <pizzuto@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-220221A (https://gcn.gsfc.nasa.gov/gcn3/31618.gcn3) in a time range of 1000 seconds centered on the alert event time (2022-02-21 00:33:59.106 UTC to 2022-02-21 00:50:39.106 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-220221A. 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-220221A 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 2e+02 GeV and 9e+04 GeV.
A subsequent search was performed including 2 days of data centered on the alert event time (2022-02-20 00:42:19.106 UTC to 2022-02-22 00:42:19.106 UTC). In this case, we report a p-value of 0.41, 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-220221A ranges from 1.6e-01 to 1.7e-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)