//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30026 SUBJECT: IceCube-210516A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 21/05/16 16:36:59 GMT FROM: Marcos Santander at U. Alabama/IceCube The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 16 May 2021 at 14:38:20.34 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 3.1 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/135292_56063172.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 16 May 2021 Time: 14:38:20.34 UT RA: 91.76 (+1.05 -0.97 deg 90% PSF containment) J2000 Dec: +9.52 ( +0.50 -0.58 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 or 3FHL catalog sources in the 90% uncertainty region. The nearest gamma-ray source in either catalog is 4FGL J0608.6+1149 at RA: 92.17 deg, Dec: 11.83 deg J2000 (2.34 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: 30029 SUBJECT: IceCube Alert 210516.61: Global MASTER-Net observations report DATE: 21/05/16 17:39:15 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (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, O.Ershova (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University) MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the IceCube Alert 210516.61 (trigger No 56063172,06h 07m 02.40s , +09d 31m 12.0s, R=0.78) errorbox 9449 sec after notice time and 9500 sec after trigger time at 2021-05-16 17:16:40 UT, with upper limit up to 16.0 mag. The observations began at zenith distance = 72 deg. The sun altitude is -18.6 deg. The galactic latitude b = -5 deg., longitude l = 200 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1614326 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 9591 | 2021-05-16 17:16:40 | MASTER-SAAO | (06h 07m 17.31s , +09d 33m 08.0s) | C | 180 | 16.0 | 9790 | 2021-05-16 17:20:00 | MASTER-SAAO | (06h 07m 24.28s , +09d 35m 15.5s) | C | 180 | 14.3 | 9990 | 2021-05-16 17:23:20 | MASTER-SAAO | (06h 07m 20.24s , +09d 34m 25.3s) | C | 180 | 15.4 | 10190 | 2021-05-16 17:26:40 | MASTER-SAAO | (06h 07m 22.59s , +09d 35m 32.8s) | C | 180 | 15.4 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30038 SUBJECT: IceCube-210516A: Upper limits from a search for additional neutrino events in IceCube DATE: 21/05/17 17:30:38 GMT FROM: Alex Pizzuto at ICECUBE/U of Wisconsin The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search for additional track-like muon neutrino events arriving from the direction of IceCube-210516A (https://gcn.gsfc.nasa.gov/gcn3/30026.gcn3) in a time range of 2 days centered on the alert event time (2021-05-15 14:38:20.340 UTC to 2021-05-17 14:38:20.340 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, one additional track-like event is found in spatial coincidence with the 90% containment region of IceCube-210516A. We find that these data are consistent with atmospheric background expectations, with a p-value of 1.0. We accordingly derive a time-integrated muon-neutrino flux upper limit at the alert position of E^2 dN/dE = 3.6 x 10^-5 TeV cm^-2 at 90% CL, under the assumption of an E^-2 power law. 90% of events IceCube would detect from a source at this declination with an E^-2 spectrum are approximately between 1 TeV and 2 PeV. A subsequent search was performed to include the month of data prior to the alert event (2021-04-16 14:38:20.340 UTC to 2021-05-17 14:38:20.340 UTC). In this case, we report a p-value of 1.0, consistent with no significant excess of track-like events, and a corresponding time-integrated muon-neutrino flux upper limit assuming an E^-2 spectrum (E^2 dN/dE) of 4.7 x 10^-5 TeV cm^-2 at the 90% CL. 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: 30041 SUBJECT: IceCube-210516A: No significant detection in HAWC DATE: 21/05/17 18:06:40 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 2021/05/16 14:38:20 UTC, the IceCube collaboration reported a track-like very-high-energy event that has a high probability of being an astrophysical neutrino, IceCube-210516A. Location is at RA: 91.76 (+1.05/-0.97 deg 90% PSF containment) J2000 Dec: 9.52 (+0.5/-0.58 deg 90% PSF containment) J2000 (GCN circular 30026). 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-value 3.0e-2 (2.9e-1 post-trials), is at RA 92.81 deg, Dec +10.01 deg (±x.xx 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 = 1.98e-13 (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 2021/05/14 23:42:33 UTC and ended 2021/05/16 23:55:20 UTC. The most significant location, with p-value 1.3e-2 (1.3e-1 post-trials), is at RA 91.93 deg, Dec +1.01 deg (±0.20 deg 68% containment) J2000. We set a time-integrated 95% CL upper limit at the position of maximum significance of: E^2 dN/dE = 4.78e-12 (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. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30046 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-210516A DATE: 21/05/18 13:37:54 GMT FROM: Sara Buson at GSFC/Fermi S. Garrappa (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 high-energy IC210516A neutrino event (GCN 30026) 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 2021-05-16 at 14:38:20.34 UT (T0) with J2000 position RA = 91.76 (+1.05, -0.97) deg, Decl. = 9.52 (+0.50, -0.58) deg (90% PSF containment). No cataloged >100 MeV gamma-ray source is located within the 90% IC210516A localization region. 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 IC210516A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC210516A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 6.6e-10 ph cm^-2 s^-1 for ~12-years (2008-08-04 to 2021-05-16 UTC), and < 6.5e-9 (< 7.1e-8) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Within the 90% confidence localization of the neutrino, 0.8 deg offset from the best-fit IC210516A position, an excess of gamma rays, Fermi J0610.5+0946, was detected in an analysis of the ~12-years integrated LAT data (100 MeV - 1 TeV) prior to T0. This putative new source is detected at a statistical significance ~4 sigma (calculated following the prescription adopted in the 4FGL). Assuming a power-law spectrum, the excess has best-fit localization of RA = 92.644 deg, Decl. = 9.782 deg (7 arcmin 68% containment, 14 arcmin 99% containment) with best-fit spectral parameters, flux = (7.4 +/- 4.2)e-9 ph cm^-2 s^-1, index = 2.7 +/- 0.3. In a preliminary analysis of the LAT data over one month prior to T0, Fermi J0610.5+0946 is not significantly detected in the LAT data. All values include the statistical uncertainty only. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of the IceCube event region 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: 30377 SUBJECT: IceCube-210516A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation DATE: 21/07/05 13:50:11 GMT FROM: Carlo Ferrigno at IAAT/ISDC V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland) J. Rodi (IAPS-Roma, Italy) A. Coleiro (APC, France) S. Mereghetti (INAF IASF-Milano, Italy) on behalf of the INTEGRAL multi-messenger collaboration: https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration Using a combination of INTEGRAL all-sky detectors (following [1]) SPI/ACS, IBIS/Veto, and IBIS, we have performed a search for a prompt gamma-ray counterpart of IceCube-210516A (GCN 30026). At the time of the event (2021-05-16 14:38:20 UTC, hereafter T0), INTEGRAL was operating in nominal mode. The peak of the event localization probability was at an angle of 130 deg with respect to the spacecraft pointing axis. This orientation implies strongly suppressed (4.5% of optimal) response of ISGRI, somewhat suppressed (60% of optimal) response of IBIS/Veto, and strongly suppressed (30% of optimal) response of SPI-ACS. The background within +/-300 seconds around the event was somewhat unstable (excess variance 1.8). We have performed a search for impulsive events in INTEGRAL SPI- ACS (as described in [2]), IBIS, and IBIS/Veto data. We do not detect any significant counterparts and estimate a 3-sigma upper limit on the 75-2000 keV fluence of 5.7e-07 erg/cm^2 (within the 50% probability containment region of the source localization) for a burst lasting less than 1 s with a characteristic short GRB spectrum (an exponentially cut off power law with alpha=-0.5 and Ep=600 keV) occurring at any time in the interval within 300 s around T0. For a typical long GRB spectrum (Band function with alpha=-1, beta=-2.5, and Ep=300 keV), the derived peak flux upper limit is ~5.4e-07 (1.3e-07) erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range. We report for completeness and in order of FAP, all excesses identified in the search region. We find: 4 likely background excesses: T-T0 | scale | S/N | flux ( x 1e-05 erg/cm2/s) | FAP -118 | 1.85 | 4.2 | 0.632 +/- 0.176 +/- 0.33 | 0.17 -189 | 4.3 | 3.4 | 0.351 +/- 0.115 +/- 0.183 | 0.374 52.2 | 0.4 | 3.8 | 1.26 +/- 0.38 +/- 0.656 | 0.515 93.7 | 0.55 | 3.8 | 1.06 +/- 0.324 +/- 0.555 | 0.753 Note that FAP estimates (especially at timescales above 2s) may be possibly further affected by enhanced non-stationary local background noise. This list excludes any excesses for which FAP is close to unity. All results quoted are preliminary. This circular is an official product of the INTEGRAL Multi-Messenger team. [1] Savchenko et al. 2017, A&A 603, A46 [2] Savchenko et al. 2012, A&A 541A, 122S