December 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 41244] GRB 251220B: Fermi GBM Final Real-time Localization
by GCN Circulars 20 Dec '25

20 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43160 SUBJECT: GRB 251220B: Fermi GBM Final Real-time Localization DATE: 25/12/20 23:48:38 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely SHORT GRB At 23:38:04 UT on 20 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251220B (trigger 787966689.62881 / 251220985). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 251.4, Dec = 47.9 (J2000 degrees, equivalent to J2000 16h 45m, 47d 53'), with a statistical uncertainty of 6.4 degrees. The angle from the Fermi LAT boresight is 40.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251220985/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251220985/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251220985/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43160. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41243] GRB 251219A: SVOM/GRM observation of a short burst
by GCN Circulars 20 Dec '25

20 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43159 SUBJECT: GRB 251219A: SVOM/GRM observation of a short burst DATE: 25/12/20 17:45:55 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Sebastien Guillot (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a short soft GRB 251219A (SVOM trigger reference: sb25121902) at 2025-12-19T02:36:31.600 UTC (T0), which is also detected by GECAM-B (Wang et al., GCN#43158). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a single pulse with a T90 of 0.16 +0.12/-0.02 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251219A.png In addition, the position of this burst, as determined by GECAM-B (RA= 296.5, DEC= -11.9, ERR=5.6), is located at about 126 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/43159. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41242] GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
by GCN Circulars 20 Dec '25

20 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43158 SUBJECT: GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645 DATE: 25/12/20 17:41:34 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by a short soft burst GRB 251219A, at 2025-12-19T02:36:31.550 UTC (denoted as T0), which is also detected by SVOM/GRM. According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of a single pulse with a duration (T90) of 0.22 +0.08/-0.16 s. The signal is mainly detected in energy lower than 200 keV. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251219A.png GECAM-B localized this burst to the following position (J2000): Ra: 274.4 deg Dec: -4.8 deg Err: 4.3 deg (1-sigma, statistical only) We note that the localization is consistent with the magnetar SGR 1830-0645. The short duration and soft spectrum also suggest this is a magnetar X-ray burst. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/43158. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41241] Fermi-LAT Gamma-ray Observations of IceCube-251218A
by GCN Circulars 20 Dec '25

20 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43157 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-251218A DATE: 25/12/20 15:25:16 GMT FROM: chiara.bartolini-1(a)unitn.it C. Bartolini (Univ. of Trento and INFN Bari), L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and S. Garrappa (Weizmann Institute of Science) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC251218A neutrino event (GCN 43151) 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 25-12-18 at 20:21:00.63 UTC (T0) with J2000 position RA = 353.60 (+0.90, -0.74) deg, Decl. = 44.15 (+0.46, -0.45) deg 90% PSF containment (J2000). One cataloged gamma-ray (>100 MeV) source is located within the 90% IC251218A localization region (4FGL-DR4, The Fourth Fermi-LAT catalog Data Release 4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). This is the unassociated gamma-ray source 4FGL J2331.6+4430. Based on a preliminary analysis of the LAT data over the timescale of 1-day and 1-month prior to T0, this object is not significantly detected (> 5 sigma). We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC251218A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC251218A best-fit position, the >100 MeV flux upper limit (95% confidence) is <9.6e-11 ph cm^-2 s^-1 for ~17-years (2008-08-04 / T0), <9.2e-09 (<8.8e-08) 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 this analysis, the Fermi-LAT contact person is C. Bartolini (chiara.bartolini at ba.infn.it). 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/43157. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41240] GRB 251220A: MAXI/GSC detection
by GCN Circulars 20 Dec '25

20 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43156 SUBJECT: GRB 251220A: MAXI/GSC detection DATE: 25/12/20 12:17:45 GMT FROM: Hitoshi Negoro at Nihon University/MAXI team <negoro.hitoshi(a)nihon-u.ac.jp> M. Uenishi (Ehime U.), H. Negoro, M. Nakajima, K. Takagi, H. Takahashi, H. Nishio (Nihon U.), T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, Y. Kawakubo, H. Hiramatsu, Y. Kondo, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima, Y. Ishihara (Chuo U.), M. Shidatsu, C. Kang, T. Nakamoto, T. Usuki, S. Yatsuzuka (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara, S. Kobayashi (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.), and S. Yamada (Tohoku U) The MAXI/GSC nova alert system triggered on a bright uncatalogued X-ray transient source at 10:37:16 UT on December 20, 2025. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (19.609 deg, -15.607 deg) = (01 18 26, -15 36 25) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.38 deg and 0.28 deg, respectively. The roll angle of long axis from the north direction is 173.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 104 +- 23 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (R.A., Dec) = (18.401, -15.400) deg = (01 13 36, -15 24 00) (J2000) (R.A., Dec) = (18.492, -16.164) deg = (01 13 58, -16 09 50) (J2000) (R.A., Dec) = (21.034, -15.868) deg = (01 24 08, -15 52 04) (J2000) (R.A., Dec) = (20.934, -15.105) deg = (01 23 44, -15 06 18) (J2000) There was no significant excess flux in the previous transit at 09:04 UT and in the next transit at 12:10 UT with an upper limit of 20 mCrab for each. View this GCN Circular online at https://gcn.nasa.gov/circulars/43156. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41239] GRB 251215A: Swift-XRT afterglow detection
by GCN Circulars 20 Dec '25

20 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43155 SUBJECT: GRB 251215A: Swift-XRT afterglow detection DATE: 25/12/20 11:59:19 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. D'Ai (INAF-IASFPA), S. Campana (INAF-OAB), A. Melandri (INAF-OAR), S. Lanava (PSU), S. Dichiara (PSU), J.A. Kennea (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has conducted further observations of the field of the Swift/BAT-detected burst GRB 251215A. The observations now extend from T0+32.0 ks to T0+383.9 ks and have a total exposure time of 9.9 ks. Of the sources previously reported, "Source 5" is fading with >3-sigma significance, and is therefore likely the GRB afterglow. Using 1629 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 122.61893, -36.74266 which is equivalent to: RA (J2000): 08h 10m 28.54s Dec(J2000): -36d 44' 33.6" with an uncertainty of 5.7 arcsec (radius, 90% confidence). This position is 97 arcsec from the Swift/BAT position. The source is fading with alpha >0.3. The results of the XRT-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/ToO_GRBs/00021894/Source5.php. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021894. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43155. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41238] IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 19 Dec '25

19 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43154 SUBJECT: IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/12/19 20:55:41 GMT FROM: Alicia Mand at IceCube/UW-Madison <aemand(a)wisc.edu> 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-251218A (https://gcn.nasa.gov/circulars/43151) in a time range of 1000 seconds centered on the alert event time (2025-12-18 20:12:40.630 UTC to 2025-12-18 20:29:20.630 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-251218A. We report a p-value of 1.00 in this time window. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, is 1.5e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-251218A 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 2e+02 GeV and 5e+04 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2025-12-17 20:21:00.630 UTC to 2025-12-19 20:21:00.630 UTC). In this case, we report a p-value of 1.00, consistent with no significant excess of track events. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, is 1.8e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-251218A 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(a)icecube.wisc.edu. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/43154. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41237] IceCube-251218A: COLIBRÍ optical upper limits
by GCN Circulars 19 Dec '25

19 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43153 SUBJECT: IceCube-251218A: COLIBRÍ optical upper limits DATE: 25/12/19 08:35:20 GMT FROM: antier(a)ijclab.in2p3.fr Sarah Antier (IJCLAB), Enrique Moreno Méndez (UNAM), Noémie Globus (UNAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Nikos Mandarakas (LAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), N. A. Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report: We observed the field of the IceCube-251218A (GCN 43151) (bronzetrack) event with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. We observed four pointings centred on (RA, Dec) = (353.8851, 44.3568), (353.3414, 44.3590), (353.8784, 43.9697), and (353.3374, 43.9697) between 2025-12-19 02:26 UTC and 03:10 UTC (from 6.09 to 6.59 hours after the trigger). At each pointing we obtained 8 minutes of simultaneous exposure in r and z over a field of 26 x 26 arcmin. These pointings cover a region of approximately 1 x 1 degree centered on (RA, Dec) = (353.60, 44.15) and cover most of the 90% uncertainty region. The data were coadded with the COLIBRÍ ASU pipeline and analysed in STDWeb/STDPipe (Karpov 2025). Comparing our observations (and after performing image subtraction) against Pan-STARRS DR1, we detect no evident uncatalogued sources within the observed fields to a 10-sigma limiting AB magnitudes of: r > 21.9 and z > 20.8 These values are not corrected for the Galactic extinction. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/43153. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41236] SVOM GRB251219.11: Global MASTER-Net observations report
by GCN Circulars 19 Dec '25

19 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43152 SUBJECT: SVOM GRB251219.11: Global MASTER-Net observations report DATE: 25/12/19 02:56:55 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) started inspect of the SVOM GRB251219.11 (trigger No 1766111792,04h 46m 20.50s , -33d 01m 10.2s, R=1) errorbox 29 sec after notice time and 58 sec after trigger time at 2025-12-19 02:37:29 UT, with upper limit up to 20.2 mag. The observations began at zenith distance = 12 deg. The sun altitude is -29.1 deg. The galactic latitude b = -39 deg., longitude l = 235 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3076431 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 63 | 2025-12-19 02:37:29 | MASTER-OAFA | (04h 46m 42.87s , -33d 06m 20.3s) | C | 10 | 19.2 | 81 | 2025-12-19 02:37:47 | MASTER-OAFA | (04h 46m 42.91s , -33d 06m 20.5s) | C | 10 | 19.2 | 104 | 2025-12-19 02:38:05 | MASTER-OAFA | (04h 46m 42.96s , -33d 06m 20.4s) | C | 20 | 19.7 | 131 | 2025-12-19 02:38:32 | MASTER-OAFA | (04h 46m 43.03s , -33d 06m 20.2s) | C | 20 | 19.8 | 184 | 2025-12-19 02:39:20 | MASTER-OAFA | (04h 46m 43.11s , -33d 06m 19.5s) | C | 30 | 18.4 | 227 | 2025-12-19 02:39:58 | MASTER-OAFA | (04h 46m 43.21s , -33d 06m 19.3s) | C | 40 | 20.1 | 278 | 2025-12-19 02:40:44 | MASTER-OAFA | (04h 46m 43.31s , -33d 06m 18.8s) | C | 50 | 20.2 | 340 | 2025-12-19 02:41:41 | MASTER-OAFA | (04h 46m 43.43s , -33d 06m 18.1s) | C | 60 | 20.2 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43152. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41235] IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 18 Dec '25

18 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43151 SUBJECT: IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/12/18 21:55:53 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-12-18 at 20:21:00.63 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 0.8234 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/141741_9008919.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 25-12-18 Time: 20:21:00.63 UT RA: 353.60 (+0.90/-0.74 deg 90% PSF containment) J2000 Dec: 44.15 (+0.46/-0.45 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 is one Fermi 4FGL-DR4 source in the 90% uncertainty region, i.e., the unassociated gamma-ray source 4FGL J2331.6+4430 at RA: 552.90 deg, Dec: 44.51 deg J2000 (0.62 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(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/43151. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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