IceCube-240929A
GCN Circular 37625
Subject
IceCube-240929A - IceCube observation of a high-energy neutrino candidate track-like event
Date
2024-09-29T14:52:14Z (8 months ago)
From
Erik Blaufuss at University of Maryland, College Park <blaufuss@umd.edu>
Via
Web form
The IceCube Collaboration (http://icecube.wisc.edu/) reports:
On 2024-09-29 at 09:55:54.03 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 0.7553 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/139912_46959751.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:
Date: 2024-06-29
Time: 09:55:54.03 UT
RA: 180.66 (+0.57, -0.71 deg 90% PSF containment) J2000
Dec: 18.92 (+0.55, -0.54 deg 90% PSF containment) J2000
No Fermi 4FGL or 3FHL catalog source are in the 90% uncertainty region. However, given the promising characteristics of the candidate neutrino event, we encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source associated with it.
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 37645
Subject
IceCube-240929A: Upper limits from a search for additional neutrino events in IceCube
Date
2024-10-01T00:07:59Z (8 months ago)
From
Jessie Thwaites at IceCube/U Wisc-Madison <thwaites@wisc.edu>
Via
Web form
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-240929A (https://gcn.nasa.gov/circulars/37625) in a time range of 1000 seconds centered on the alert event time (2024-09-29 09:47:34.030 UTC to 2024-09-29 10:04:14.030 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-240929A. 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-240929A 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 (2024-09-28 09:55:54.030 UTC to 2024-09-30 09:55:54.030 UTC). In this case, we report a p-value of 0.12, 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-240929A 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.
[1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021)
GCN Circular 37652
Subject
Fermi-LAT Gamma-ray Observations of IceCube-240929A
Date
2024-10-01T10:42:29Z (8 months ago)
From
Simone Garrappa at Weizmann Institute of Science <simone.garrappa@weizmann.ac.il>
Via
Web form
S. Garrappa (Weizmann Institute of Science), C. Bartolini (INFN Bari), L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and J. Sinapius (DESY) on behalf of the Fermi-LAT collaboration:
We report an analysis of observations of the vicinity of the high-energy IC240929A neutrino event (GCN 37625) 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 2024-09-29 09:55:54.03 UTC (T0) with J2000 position RA = 180.66 (+0.57, -0.71) deg, Decl. = 18.92 (+0.55, -0.54) deg 90% PSF containment. No Fermi 4FGL catalog gamma-ray source is located within the 90% IC-240929A localization error (Fourth Fermi-LAT catalog, 4FGL-DR4, The Fermi-LAT collaboration 2023, arXiv:2307.12546).
We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (>100 MeV) within the IC240929A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IceCube best-fit position, the >100 MeV flux upper limit (95% confidence) is <3.0e-9 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), <5.6e-9 (< 5.5e-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 source will continue. For these observations, the Fermi-LAT contact person is S. Garrappa (simone.garrappa at weizmann.ac.il). 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.