//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31929 SUBJECT: IceCube Alert 220421.22: Global MASTER-Net observations report DATE: 22/04/21 05:39:20 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, E.Gorbovskoy, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, G.Antipov, D.Zimnukhov, V.Senik, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D.Cheryasov, Ya.Kechin (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev (Irkutsk State University, API), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational State University) MASTER-OAGH robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Mexico (OAGH National Institute for Astrophysics, Optics and Electronics) was pointed to the IceCube Alert 220421.22 (trigger No 43687362,07h 37m 27.60s , +06d 02m 13.2s, R=0.74) errorbox 314 sec after notice time and 361 sec after trigger time at 2022-04-21 05:26:19 UT, with upper limit up to 17.8 mag. The observations began at zenith distance = 67 deg. The sun altitude is -39.6 deg. The galactic latitude b = 14 deg., longitude l = 213 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1949987 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 396 | 2022-04-21 05:26:19 | MASTER-OAGH | (07h 37m 41.98s , +06d 02m 00.1s) | C | 70 | 17.0 | 396 | 2022-04-21 05:26:19 | MASTER-OAGH | (07h 37m 05.71s , +06d 30m 58.4s) | P- | 70 | 16.8 | 653 | 2022-04-21 05:30:10 | MASTER-OAGH | (07h 37m 05.77s , +06d 29m 03.1s) | P- | 120 | 17.1 | 653 | 2022-04-21 05:30:10 | MASTER-OAGH | (07h 37m 42.24s , +06d 00m 03.1s) | C | 120 | 17.8 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31931 SUBJECT: IceCube-220421A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 22/04/21 11:45:13 GMT FROM: Marcos Santander at U. Alabama/IceCube The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 2022-04-21 at 05:20:18.26 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 2.281 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/136556_43687362.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 2022-04-21 Time: 05:20:18.26 UT RA: 113.64 (+3.17, -2.74 deg 90% PSF containment) J2000 Dec: 5.83 (+2.18, -1.69 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% containment region for the event: the source 4FGL J0733.8+0455 (RA: 113.47 deg, Dec: 4.93 deg J2000), 0.92 deg 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 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31935 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-220421A DATE: 22/04/22 20:25:56 GMT FROM: Simone Garrappa at DESY 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 IC220421A neutrino event (GCN 31931) 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 2022-04-21 at 05:20:18.26  UT (T0) with J2000 position RA = +113.64 (+3.17, -2.74) deg, Decl. = +5.83 (+2.18, -1.69) deg (90% PSF containment). One cataloged gamma-ray (>100 MeV) source is located within the 90% IC220421A localization region (4FGL-DR3; arXiv:2201.11184; The Fermi-LAT collaboration 2020, ApJS, 247, 33). This is 4FGL J0733.8+0455, associated with the high-redshift blazar CGRaBS J0733+0456 (z =3.01; Healey et al. 2008 ApJS, 175, 97). 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 IC220421A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC220421A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 2.0e-10 ph cm^-2 s^-1 for ~13-years (2008-08-04 to 2022-04-21 UTC), and < 5.3e-9 (< 4.8e-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) 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: 31969 SUBJECT: IceCube-220421A: Upper limits from a search for additional neutrino events in IceCube DATE: 22/04/29 16:11:58 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-220421A (https://gcn.gsfc.nasa.gov/gcn3/31931.gcn3) in a time range of 1000 seconds centered on the alert event time (2022-04-21 05:11:58.260 UTC to 2022-04-21 05:28:38.260 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-220421A. 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-220421A ranges from 1.3e-01 to 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 3e+02 GeV and 1e+05 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2022-04-20 05:20:18.260 UTC to 2022-04-22 05:20:18.260 UTC). In this case, we report a p-value of 0.06, 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-220421A ranges from 1.5e-01 to 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)