//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23214 SUBJECT: IceCube-180908A - IceCube observation of a high-energy neutrino candidate event DATE: 18/09/09 02:49:16 GMT FROM: Erik Blaufuss at U. Maryland/IceCube The IceCube Collaboration (http://icecube.wisc.edu/) reports:. On September 8, 2018, IceCube detected a track-like, very-high-energy event with a high probability of being of astrophysical origin. The event was identified by the Extremely High Energy (EHE) track event selection. The IceCube detector was in a normal operating state. EHE events typically have a neutrino interaction vertex that is outside the detector, produce a muon that traverses the detector volume, and have a high light level (a proxy for energy). After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon/34507973_131475.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 18/09/08 Time: 19:59:31.84 UT RA: 144.58 [-1.45,+1.55] (deg 90% PSF containment) J2000 Dec: -2.13 [-1.2,+0.9] (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. 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: 23218 SUBJECT: Search for counterpart to IceCube-180908A with ANTARES DATE: 18/09/10 07:38:51 GMT FROM: Damien Dornic at CPPM,France Alexis Coleiro (APC) and Damien Dornic (CPPM) report on behalf of the ANTARES Collaboration: Using data from the ANTARES detector, we have performed a follow-up analysis of the recently reported single high-energy (EHE) neutrino IceCube-180908A (GCN 23214). The reconstructed origin was 40.7 degrees below the horizon for ANTARES. No up-going muon neutrino candidate events were recorded within three degrees of the IceCube event coordinates during a +/- 1h time-window centered on the IceCube event time. A search over an extended time window of +/- 1 day has also yielded no detection (52% visibility probability). This yields a preliminary 90% confidence level upper limit on the muon-neutrino fluence from a point source of 18 GeV.cm^-2 over the energy range 2.4 TeV - 2.6 PeV (the range corresponding to 5-95% of the detectable flux) for an E^-2 power-law spectrum, and 36 GeV.cm^-2 (400 GeV - 250 TeV) for an E^-2.5 spectrum. ANTARES is the largest neutrino detector installed in the Mediterranean Sea, and is primarily sensitive to astrophysical neutrinos in the TeV-PeV energy range. At 10 TeV, the median angular resolution for muon neutrinos is below 0.5 degrees. In the range 1-100 TeV, ANTARES has a competitive sensitivity to this position in the sky. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23219 SUBJECT: IceCube-180908A: HAWC follow-up DATE: 18/09/11 00:51:53 GMT FROM: Israel Martinez at HAWC Israel Martinez (University of Maryland) and Ignacio Taboada (Georgia Tech) report on behalf of the HAWC collaboration (https://www.hawc-observatory.org/collaboration/): On 2018/09/08 19:59:31.84 UT IceCube detected a track-like, very-high-energy event with a high probability of being of astrophysical origin, at RA=144.58d and Dec=-2.13d J2000 as reported in GCN circular 23214. The event was not in the field of view of HAWC, so we analyze the data in three timescales: *We searched for a steady source in archival data from November 2014 to April 2018. Assuming a spectral index of -2.5 we searched in the reported 90% PSF containment circle.The maximum significance is 1.2 sigma at RA=143.9deg and Dec=-1.8deg. We estimate the number of trials to be ~40. We set an upper limit 95% CL on gamma rays for this period of: E^2 dN/dE = 6.4e-13 (E/TeV)^-0.5 TeV cm^-2 s^-1. *We searched using data corresponding to the month previous to the IceCube-180908A alert (MJD 58340.674-58370.815). Using the same spectral index and search window, the maximum significance is 1.0 sigma at RA=144.7deg and Dec=-2.8deg. We set an upper limit 95% CL on gamma rays for this period of: E^2 dN/dE = 2.9e-12 (E/TeV)^-0.5 TeV cm^-2 s^-1. *We also performed a study using data corresponding to the two nearest transits of IceCube-180908A in HAWC’s field of view (MJD 58369.59-58369.81 and 58370.59-58370.81). Using the same spectral index and search window, the maximum significance is 0.6 sigma at RA=145.0deg and Dec=-1.8deg. We set an upper limit 95% CL on gamma rays for this period of: E^2 dN/dE = 1.6e-11 (E/TeV)^-0.5 TeV cm^-2 s^-1. HAWC is a very-high-energy gamma-ray observatory located in Central Mexico at latitude 19 deg North. It operates 24 hours per day 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: 23220 SUBJECT: Search for counterparts to IceCube-180908A with IceCube DATE: 18/09/11 02:30:37 GMT FROM: Alex Pizzuto at ICECUBE/U of Wisconsin The IceCube Collaboration (http://icecube.wisc.edu/) reports: We report on additional observations of IceCube-180908A, GCN 23214 by the IceCube Neutrino Observatory. IceCube has performed a search for additional track-like muon neutrino events arriving from the direction of the IceCube-180908A alert (https://gcn.gsfc.nasa.gov/gcn3/23214.gcn3) in a time range of 2 days centered on the alert event time (2018-09-07 19:59:31.84 to 2018-09-09 19:59:31.84) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, two additional neutrino track events are found in spatial coincidence with IceCube-180908A with a p-value of 0.027 (1.9 sigma). Accordingly, these tracks would represent a time-integrated muon-neutrino flux normalization assuming an E^-2 spectrum (E^2 dN/dE) at the 90% CL of 1.39 x 10^-5 TeV cm^-2 (+2.20, -1.09) ( 4.46 x 10^-5 TeV cm^-2 flux upper limit at the 90% CL) for this observation period. A subsequent search was performed to include the previous month of data (2018-08-08 19:59:31.84 to 2018-09-09 19:59:31.84). In this case, we report a p-value of 1.0, consistent with no significant excess of track events, and a corresponding time-integrated muon-neutrino flux upper limit assuming an E^-2 spectrum (E^2 dN/dE) at the 90% CL of 5.32 x 10^-5 TeV cm^-2. 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: 23221 SUBJECT: INTEGRAL observation of IceCube-180908A DATE: 18/09/11 06:17:41 GMT FROM: Volodymyr Savchenko at ISDC,U of Geneve V. Savchenko, C. Ferrigno (ISDC, University of Geneva, CH) P. Ubertini, A. Bazzano, L. Natalucci, J. Rodi (INAF IAPS-Roma, Italy) S. Mereghetti (INAF IASF-Milano, Italy) P. Laurent (CEA, Saclay, France) E. Kuulkers (ESTEC/ESA, Noordwijk, The Netherlands) Using INTEGRAL, we have performed a search for a prompt gamma-ray counterpart of the cosmic neutrino candidate IceCube-180908A (GCN 23214). At the time of the event (2018-09-08 19:59:32 UTC, hereafter T0), INTEGRAL was operating in nominal mode. The peak of the neutrino localization probability was at an angle of 80 deg with respect to the spacecraft pointing axis. This orientation implies a strongly suppressed response of IBIS, and somewhat suppressed response of SPI-ACS. The background within ±300 seconds around the event was very stable.  We do not detect any significant counterpart and estimate a 3-sigma upper limit on the 75-2000 keV fluence of 2.8e-07 erg/cm^^2 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 ~3.2e-07 (9.4e-07) erg/cm^^2 /s at 1 s (8 s) time scale in 75-2000 keV energy range. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23222 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-180908A DATE: 18/09/11 19:51:42 GMT FROM: Sara Buson at GSFC/Fermi S. Buson (NASA-GSFC), S. Garrappa (DESY-Zeuthen), M. Kreter (Univ. of Würzburg), J. Eggen (NASA-GSFC, University of Maryland) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the very high-energy IC180908A neutrino event (GCN 23214) 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 2018-09-08 19:59:31.84 UTC (T0) with J2000 position, RA =144.58 deg, Decl. = -2.13 deg. There are no cataloged >100 MeV gamma-ray sources consistent with the IC180908A localization. The closest cataloged gamma-ray source is 3FGL J0948.8+0021, associated with the narrow-line Seyfert I PMN J0948+0022 (Ackermann et al. 2015 ApJS 810, 14), at a distance of roughly 3.6 deg. 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) excess emission (0.1 - 300 GeV) within the IC180908A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.2 fixed) for a point source at the IceCube position, the >100 MeV flux upper limit (95% confidence) is < 1.6e-9 ph cm^-2 s^-1 for a 1-year integration time before T0. Within the error circle for the direction of the neutrino, a ~3.9 sigma excess of gamma rays, Fermi J0935-0227, was identified integrating the LAT data (0.1 - 300 GeV) between 2008-08-04 and 2018-03-16. Assuming a power-law spectrum, the candidate source has best-fit localization of RA: 143.85, Dec: -2.46 (0.18 deg 99% containment) with best fit spectral parameters flux = (1.0 +/- 0.6)e-9 ph cm^-2 s^-1, index = 2.0 +/- 0.2. The blazar CRATES J0935-0241 is outside the 99% LAT error region, 0.22deg away from the position of the gamma-ray excess, while within the IC180908A 90% PSF containment. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. During the upcoming weeks (Fermi mission week 357/359), starting on Sept. 13 2018, the Fermi-LAT will be rocking preferentially toward the northern hemisphere, enabling low but continuous exposure to the IC180908A region. For this source the Fermi-LAT contact persons are S. Buson (e-mail: sara.buson at gmail.com), S. Garrappa (simone.garrappa at desy.de) and M. Kreter (mkreter at astro.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: 23224 SUBJECT: IceCube-180908A: CALET Gamma-Ray Burst Monitor upper limits DATE: 18/09/13 12:59:09 GMT FROM: Takanori Sakamoto at AGU S. Ricciarini (U of Florence), A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita, Y. Kawakubo, A. Tezuka, S. Matsukawa, H. Onozawa, T. Ito, H. Morita, Y. Sone (AGU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), I. Takahashi (IPMU), Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR), M. L. Cherry (LSU), A. V. Penacchioni, P. S. Marrocchesi (U of Siena) and the CALET collaboration: We have performed a search of hard X-ray/gamma-ray counterpart to the IceCube neutrino event IceCube-180908A (The IceCube Collaboration, GCN Circ. 23214) in the CALET Gamma-ray Burst Monitor (CGBM) data around the event time at T0=19:59:31.84 UT on 2018 September 8. The event position (RA, Dec (J2000) = 144.58 [-1.45,+1.55] deg, -2.13 [-1.2,+0.9] deg) at that time was in the CGBM FOV at favorable angles (the off-axis angles 19 deg and 16 deg for HXM and SGM detector respectively). No CGBM on-board trigger occurred around T0 (the nearest GRB triggered CGBM at 20:28:41.478 UTC on 9 August 2018: Cherry et al., GCN 23116; all subsequent CGBM triggers were due to local particles). By using the CGBM time-history data (0.125 sec time resolution), we found no statistically significant signal within T0 +- 800 sec interval in either the HXM (7-3000 keV) or the SGM (40 keV - 28 MeV) data. We estimate 7-sigma upper limit in the 40-1000 keV band as 6.7 x 10^-7 erg/cm2/s assuming a simple power-law model with a photon index of -2 and 7.5 x 10^-7 erg/cm2/s assuming a GRB (Band) model with the typical parameters for long GRBs: alpha = -1.0, Ep = 300 keV, and beta = -2.5 (both in 1 sec exposure). The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.