//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 33552 SUBJECT: IceCube-230401A: IceCube observation of a high-energy neutrino candidate DATE: 23/04/01 17:13:32 GMT FROM: Cristina Lagunas Gualda at DESY The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 23-04-01 at 16:14:18.91 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 4.11 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/137794_38132005.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 23-04-01 Time: 16:14:18.91 UT RA: 8.17 (+4.26/-2.91 deg 90% PSF containment) J2000 Dec: +1.94 (+2.44/-1.96 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 several Fermi 4FGL or 3FHL catalog sources in the 90% uncertainty region. The nearest gamma-ray source is 4FGL J0038.1+0012 at RA: 9.54 deg, Dec: 0.21 deg (2.20 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: 33560 SUBJECT: IceCube-230401A: Upper limits from a search for additional neutrino events in IceCube DATE: 23/04/04 01:18:04 GMT FROM: Jessie Thwaites at IceCube/U Wisc-Madison 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-230401A (https://gcn.gsfc.nasa.gov/gcn3/33552.gcn3) in a time range of 1000 seconds centered on the alert event time (2023-04-01 16:05:58.900 UTC to 2023-04-01 16:22:38.900 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-230401A. 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-230401A ranges from 1.4e-01 to 1.5e-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 2e+05 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2023-03-31 16:14:18.900 UTC to 2023-04-02 16:14:18.900 UTC). In this case, we report a p-value of 0.05, 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-230401A 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. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 33561 SUBJECT: Fermi-LAT gamma-ray observations of IceCube-230401A and detection of Fermi J0030.2+0005 DATE: 23/04/04 11:26:36 GMT FROM: Sara Buson at GSFC/Fermi S. Garrappa (Ruhr-Universitaet Bochum), J. Sinapius (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg) and C. C. Cheung (Naval Research Laboratory) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the IC230401A high-energy neutrino event (GCN 33552) 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 2023-04-01 at 16:14:18.91 UT (T0) with J2000 position RA = 8.17 (+4.26, -2.91) deg, Decl. = +1.94 (+2.44, -1.96) deg (90% PSF containment). Three cataloged gamma-ray (>100 MeV; The Fermi-LAT collaboration 2022, ApJS, 260, 53) sources are located within the 90% IC230401A localization region. These are the sources 4FGL J0022.0+0006, 4FGL J0024.7+0349 and 4FGL J0038.1+0012. Based on a preliminary analysis of the LAT data over a month and day timescale prior T0, these objects are not significantly detected at gamma rays. 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 IC230401A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC230401A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 1.2e-10 ph cm^-2 s^-1 for ~14-years (2008-08-04 to 2023-04-01 UTC), and < 2.5e-8 (<1.2e-7) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. In the analysis of the ~14-years integrated LAT data (100 MeV - 1 TeV), a 4.5 sigma new excess of gamma rays, Fermi J0030.2+0005, was detected 2 deg offset from the best-fit IC230401A position and within the 90% confidence localization of the direction of the neutrino. Assuming a power-law spectrum, the best-fit localization is (J2000) RA: 7.56 deg, Dec: 0.09 deg (9 arcmin 99% containment, 5 arcmin 68% containment). The gamma-ray best-fit spectral parameters are flux = (1.7 +/- 0.9)e-9 ph cm^-2 s^-1 and index = 2.3+/-0.2. In a preliminary analysis of the LAT data over 1-day and 1-month prior T0, Fermi J0030.2+0005 is not significantly detected in the LAT data. All values include the statistical uncertainty only. The statistical significance is calculated following the prescription adopted in the 4FGL. A possible counterpart of Fermi J0030.2+0005 is the blazar object 5BZBJ0030-0000 at RA=7.53283 deg, Dec=-0.002 deg (Massaro et al. 2015 Ap&SS, 357, 1). This source is located about 6 arcmin from the Fermi J0030.2+0005 best-fit position, and within the gamma-ray 99% positional uncertainty. 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 ruhr-uni-bochum.de ), J. Sinapius (jonas.sinapius 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.