//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31692 SUBJECT: IceCube-220306A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 22/03/06 05:13:34 GMT FROM: Erik Blaufuss at U. Maryland/IceCube The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 2022-03-06 at 03:46:37.06 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 0.45 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/136392_25495567.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 2022-03-06 Time: 03:46:37.06 UT RA: 314.82 (+0.54/-0.52 deg 90% PSF containment) J2000 Dec: +8.61 (+0.47/-0.55 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-DR2 or 3FHL catalog sources in the 90% uncertainty region. The nearest gamma-ray source in the 4FGL-DR2 catalog is 4FGL J2101.3+0912 at RA: 315.35 deg, Dec: 9.20 deg (in J2000 coordinates, 0.79 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 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31706 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-220306A DATE: 22/03/07 18:14:25 GMT FROM: Simone Garrappa at DESY S. Garrappa (DESY-Zeuthen), 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 high-energy IC220306A neutrino event (GCN 31692) 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 2022-03-06 03:46:37.06 UTC (T0) with J2000 position RA = 314.82 (+0.54, -0.52) deg, Decl. = 8.61 (+0.47, -0.55) deg 90% PSF containment. No cataloged gamma-ray sources are found within the 90% IC220306A localization error (4FGL-DR3; arXiv:2201.11184; The Fermi-LAT collaboration 2020, ApJS, 247, 33). We searched for the existence of intermediate (months to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC220306A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC220306A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 1.3e-10 ph cm^-2 s^-1 for ~13-years (2008-08-04 to 2022-03-06 UTC), <4.6e-9 (< 1.3e-7) 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 this source 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. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31709 SUBJECT: IceCube-220306A: Upper limits from a search for additional neutrino events in IceCube DATE: 22/03/08 15:14:33 GMT FROM: Alex Pizzuto at ICECUBE/U of Wisconsin 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-220306A (https://gcn.gsfc.nasa.gov/gcn3/31692.gcn3) in a time range of 1000 seconds centered on the alert event time (2022-03-06 03:38:17.060 UTC to 2022-03-06 03:54:57.060 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-220306A. 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-220306A 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 (2022-03-05 03:46:37.060 UTC to 2022-03-07 03:46:37.060 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-220306A 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. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31722 SUBJECT: IceCube-220306A: No significant detection in HAWC DATE: 22/03/09 19:53:38 GMT FROM: Hugo Ayala at Pennsylvania State University Hugo Ayala (Penn State) reports on behalf of the HAWC collaboration (http://www.hawc-observatory.org/collaboration): On 2022/03/06 03:46:37 UTC, the IceCube collaboration reported a track-like very-high-energy event that has a high probability of being an astrophysical neutrino, IceCube-220306A. Location is at RA: 314.82 (+0.54/-0.52 deg 90% PSF containment) J2000 Dec: 8.61 (+0.47/-0.55 deg 90% PSF containment) J2000 (GCN circular 31692). 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-value1.39e-2 (7.42e-2 post-trials), is at RA 314.65 deg, Dec 8.73 deg (±0.30 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 = 5.6281e-14 (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 2022/03/04 19:24:48 UTC and ended 2022/03/06 19:33:12 UTC . The most significant location, with p-value 8.69e-02 (3.94e-01 post-trials), is at RA 314.85 deg, Dec 8.05 deg (±0.24 deg 68% containment) J2000. We set a time-integrated 95% CL upper limit at the position of maximum significance of: E^2 dN/dE = 1.1577e-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.