//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24028 SUBJECT: IceCube-190331A - IceCube observation of a high-energy neutrino candidate event DATE: 19/03/31 19:12:37 GMT FROM: Claudio Kopper at IceCube/U of Alberta The IceCube Collaboration (http://icecube.wisc.edu/) reports: On March 31, 2019, IceCube detected a track-like, very-high-energy event with a high probability of being produced by a muon neutrino of astrophysical origin. The event was identified by the High Energy Starting Event (HESE) track selection. The IceCube detector was in a normal operating state. HESE tracks have a neutrino interaction vertex inside the detector and produce a muon that only partially traverses the detector volume, and have a high light level (a proxy for energy). After the initial automated alert was issued, visual inspection of the event revealed that the online directional reconstruction reported in the original GCN (https://gcn.gsfc.nasa.gov/notices_amon/15947448_132379.amon) was very incorrect, biased by the topology of the event. More sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 2019/03/31 Time: 06:55:43.44 UT RA: 337.68deg (+0.23deg -0.34deg 90% PSF containment) J2000 Dec: -20.70deg (+0.30deg -0.48deg 90% PSF containment) J2000 Additionally, given the large deposited energy observed in this event (one of the highest observed so far), it has a very high likelihood of being of astrophysical origin. We strongly 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 catalog sources in the 90% region. The nearest source is 1RXS J223249.5-202232 (4FGL J2232.6-2023) at RA: 338.1725deg, Dec: -20.3909deg. 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: 24034 SUBJECT: IceCube-190331A: MASTER optical follow-up observations DATE: 19/04/01 11:56:39 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, N.Tyurina, V.Kornilov, D.Vlasenko, V.Vladimirov, D.Zimnukhov, A.Kuznetsov, P.Balanutsa, A. Chasovnikov, V.Topolev, F.Balakin, K.Zhirkov, D.Kuvshinov (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C. Lopez, C.Francile, F. Podesta (Observatorio Astronomico Felix Aguilar OAFA, San Juan National University), H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE, SJNU) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O. Gress, N.M. Budnev, O.Ershova, S.Yazev (Applied Physics Institute, Irkutsk State University), V. Yurkov, A. Gabovich, Yu. Sergienko, D. Kobcev (Blagoveschensk Educational State University), A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), MASTER-OAFA robotic telescope (Global MASTER-Net http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy,vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of IceCube 190331A error-box (Kopper et al. GCN24028, center RA,Dec=337.68deg, -20.70deg) at 2019-04-01 09:04:32UT (when error-box_altitude=12 deg, sun_alt=27 deg.) with mlim=19.1 . There is NGC 7293 (Helix Nebula) inside IC error-box with 10^4 yrs age http://master.sai.msu.ru/static/IC/MASTERIceCube-190331A.jpg Reduction will be continued. MASTER Global Robotic Net received to socket IceCube alert 190331.29 with coordinates RA,Dec=355.6349 +71.1170 (J2000) and error-box 8.9deg. http://master.sai.msu.ru/static/IC/IC190331.29.txt and automatically inspected this localization by MASTER-Tunka, MASTER-Kislovodsk, MASTER-Tavrida http://master.sai.msu.ru/static/IC/MASTERIC190331.29map.jpg with mlim 18-20mag. If new coordinates from GCN 24028 by Kopper et al. were sent automatically to subscribers, IceCube could get follow-up in time. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24039 SUBJECT: Search for additional neutrino events from the direction of IceCube-190331A with IceCube DATE: 19/04/01 16:26:27 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-190331A (https://gcn.gsfc.nasa.gov/gcn3/24028.gcn3) in a time range of 2 days centered on the alert event time (2019-03-30 06:55:43.44 UTC to 2019-04-01 06:55:43.44 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero additional track-like events are found in spatial coincidence with the 90% PSF containment of IceCube-190331A. We find that these data are well described by atmospheric background expectations, with a p-value of 1.0. Accordingly, these data would represent a time-integrated muon-neutrino flux upper limit assuming an E^-2 spectrum (E^2 dN/dE) at the 90% CL of 3.0 x 10^-4 TeV cm^-2 for this observation period. 90% of events IceCube would detect from a source at this declination with an E^-2 spectrum are between approximately 10 TeV and 1 PeV. A subsequent search was performed to include the previous month of data (2019-03-01 06:55:43.44 UTC to 2019-04-01 06:55:43.44 UTC). In this case, we also 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 3.8 x 10^-4 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: 24040 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-190331A DATE: 19/04/01 16:29:06 GMT FROM: Sara Buson at GSFC/Fermi S. Buson (Univ. of Wuerzburg, UMBC) and S. Garrappa (DESY-Zeuthen) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC190331A neutrino event (GCN 24028) 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 2019-03-31 06:55:43.44 UT (T0) with J2000 position RA = 337.68 (+0.23, -0.34) deg, Decl. = -20.70 (+0.30, -0.48) deg 90% PSF containment. No cataloged gamma-ray sources are found within the 90% IC190331 localization error. 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 (0.1 - 300 GeV) within the IC190331A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.2 fixed) for a point source at the IceCube best-fit position, the >100 MeV flux upper limit (95% confidence) is < 1.5e-10 ph cm^-2 s^-1 for ~10.8-years (2008-08-04 / 2019-03-31 UTC), < 1.2e-8 ph cm^-2 s^-1 for a 1-month 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 Sara Buson (sara.buson at astro.uni-wuerzburg.edu) and Simone Garrappa (simone.garrappa at desy.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: 24094 SUBJECT: IceCube-190331A: Swift-XRT Follow-up Observations DATE: 19/04/10 18:28:22 GMT FROM: Azadeh Keivani at Columbia U A. Keivani (Columbia U.), M. Santander (U. Alabama), J. A. Kennea (PSU), P. A. Evans (U. Leicester), D. B. Fox (PSU), & F. Krauss (GRAPPA/API, University of Amsterdam) report: The Neil Gehrels Swift Observatory observed the field of the IceCube HESE astrophysical neutrino candidate event IceCube-190331A (revision 1, https://gcn.gsfc.nasa.gov/gcn3/24028.gcn3) beginning April 9, 07:42:23 UT. Prompt observation of the neutrino localization was not possible as it was initially within the Sun avoidance region for Swift. Observations commenced 9 days after the event detection once the angular distance to the Sun had increased. Swift utilized its onboard 7-point tiling pattern to cover a region centered on R.A., Dec. (J2000) = 337.68d, -20.70d, with a radius of approximately 33 arcmin; estimated 90%-containment radii for this event are 0.23d to 0.48d depending on position angle. Swift-XRT collected ~800 s per field of PC mode data per tile between 07:45:27 UT and 11:18:04 UT on 9 April. Data have been reduced using the analysis approach and software routines of Evans et al. 2014 (ApJS, 210, 8). Four X-ray sources (one marginal) are detected in these observations, three of which are previously uncatalogued and relatively low in flux, consistent with expectations for serendipitous (unrelated) sources over a region of this extent. The highest-significance X-ray source is located at R.A. 337.35513, Dec. -20.31324 (J2000), within the IceCube 90%-containment region, and matches the known X-ray source 1WGA J2229.4-2018 from ROSAT/WGACAT (15.37 arcsec distance). The source is listed in the Milliquas catalog (Flesch 2017) as the likely active galactic nucleus (AGN) WISEA J222925.59-201846.0, a 2MASS extended source with J~16 mag and photometric redshift z~0.6. We recover it at a mean observed XRT count rate of 1.2 (+0.6, -0.5) e-2 ct s^-1, consistent with (1.5-sigma above) its WGACAT flux. Although this AGN is not an obvious counterpart to the high-energy neutrino, investigation of its properties continues. Excluding identified sources, the 3-sigma upper limit on the count rate of any point-like counterpart over the rest of the tiled region is 0.01 ct s^-1, which corresponds to a 0.3-10 keV flux of 4.0e-13 erg cm^-2 s^-1 for a typical AGN spectrum (nH=3e20 cm^-2, Gamma=1.7). Coordinates and count rates for the lower-significance X-ray sources are provided below. Source #2: R.A. 337.52845d, Dec. -21.09942d, 9 (+5, -3) e-3 XRT ct s^-1 Source #3: R.A. 338.02509d, Dec. -21.04924d, 10 (+5, -4) e-3 XRT ct s^-1 Source #4 (marginal): R.A. 338.01838d, Dec. -21.11994d, 9 (+7, -5) e-3 XRT ct s^-1