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[vsnet-grb-info 41151] IceCube-251210A: DDOTI Optical Upper Limit
by GCN Circulars 11 Dec '25

11 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43071 SUBJECT: IceCube-251210A: DDOTI Optical Upper Limit DATE: 25/12/11 05:40:15 GMT FROM: Rosa Leticia Becerra at Instituto de Astronomía, UNAM <rbecerra(a)astro.unam.mx> Rosa L. Becerra (UNAM), Simone Dichiara (Penn State University), Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Nat Butler (ASU), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM), Margarita Pereyra (UNAM) and Eleonora Troja (U Roma) report: We observe the field of the IceCube-251210A (gold) event (IceCube Collaboration, GCN Circ. 43064) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on the Sierra of San Pedro Martir (http://ddoti.astroscu.unam.mx) on the night of 2025-12-11 UTC. DDOTI observed from 01:54 UTC to 04:34 UTC (T+14.8 h to T+17.5 h after the trigger), with a total exposure time of 81 minutes, covering the entire error region reported by IceCube (IceCube Collaboration, GCN Circ. 43064). Comparing our observations to the USNO-B1 and PanSTARRS PS1 DR2 catalogues, we detect no uncatalogued or credible fading sources within the observed field to a 10-sigma limiting AB magnitude of: w > 20.5 Further observations are planned to assess variability. This value is not corrected for the Galactic extinction. We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir View this GCN Circular online at https://gcn.nasa.gov/circulars/43071. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41150] SVOM GRB251211.12: Global MASTER-Net observations report
by GCN Circulars 11 Dec '25

11 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43070 SUBJECT: SVOM GRB251211.12: Global MASTER-Net observations report DATE: 25/12/11 03:00:33 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 GRB251211.12 (trigger No 1765421306,03h 46m 48.22s , +23d 45m 06.5s, R=1) errorbox 27 sec after notice time and 61 sec after trigger time at 2025-12-11 02:49:27 UT, with upper limit up to 18.7 mag. The observations began at zenith distance = 55 deg. The sun altitude is -31.1 deg. The galactic latitude b = -23 deg., longitude l = 167 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3067906 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 67 | 2025-12-11 02:49:27 | MASTER-OAFA | (03h 47m 09.45s , +23d 52m 13.3s) | C | 10 | 18.7 | 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/43070. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41149] GRB 251211A: Fermi GBM Final Real-time Localization
by GCN Circulars 11 Dec '25

11 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43069 SUBJECT: GRB 251211A: Fermi GBM Final Real-time Localization DATE: 25/12/11 02:51:35 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 LONG GRB At 02:40:59 UT on 11 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251211A (trigger 787113664.18548 / 251211112). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 181.9, Dec = -32.3 (J2000 degrees, equivalent to J2000 12h 07m, -32d 17'), with a statistical uncertainty of 6.4 degrees. The angle from the Fermi LAT boresight is 28.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251211112/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251211112/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251211112/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43069. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41148] GRB 251209A: Fermi GBM observation
by GCN Circulars 10 Dec '25

10 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43068 SUBJECT: GRB 251209A: Fermi GBM observation DATE: 25/12/10 22:23:56 GMT FROM: Elisabetta Bissaldi at Politecnico and INFN Bari <elisabetta.bissaldi(a)ba.infn.it> E. Bissaldi (Politecnico and INFN Bari) reports on behalf of the Fermi GBM Team: "At 13:24:03.99 UT on 9 December 2025, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 251209A (trigger 786979448 / 251209558). The Fermi GBM Final Real-time Localization is reported in GCN 43048. The angle from the Fermi LAT boresight at the GBM trigger time is 52 degrees. The GBM light curve consists of several structured emission episodes with a duration (T90) of about 57 s (50-300 keV). The time-averaged spectrum from T0-4 s to T0+81 s is best fit by a Band function with Epeak = 105 +/- 4 keV, alpha = -1.63 +/- 0.01, and beta = -2.37 +/- 0.06. The event fluence (10-1000 keV) in this time interval is (6.89 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+49.7 s in the 10-1000 keV band is 38.4 +/- 0.6 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/43068. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41147] GRB 251205A: 1.3m DFOT optical upper limit
by GCN Circulars 10 Dec '25

10 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43067 SUBJECT: GRB 251205A: 1.3m DFOT optical upper limit DATE: 25/12/10 20:44:22 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Debalina Kar, Koshvendra Singh, Dhruv Jain, Pankaj Pawar, and Kuntal Misra (ARIES) report: We observed the field of GRB 251205A detected by Swift (Lanava et al. 2025, GCN 43005) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2025-12-09 at 23:15:22.00 UT, i.e., ~ 3.98 days after the Swift trigger. We have taken multiple frames with an exposure time of 300s in the R filter. We stacked the images after the alignment. We could not detect the optical emission in our stacked image within the error box of Swift/UVOT (Lanava et al. 2025, GCN 43005). We obtain the following 3-sigma upper limit in the stacked image: Date Start_UT T_start-T0 (Days) Filter Exp time (s) Magnitude =============================================================== 2025-12-09 23:15:22.00 ~3.98 R 300s*11 >22.9 The non-detection of the burst is consistent with (Lipunov et al. 2025, GCN 43004; Lanava et al. 2025, GCN 43005; Lipunov et al. 2025, GCN 43006; de Ugarte Postigo et al. 2025, GCN 43008; Malesani et al. 2025, GCN 43009; O’Neill et al. 2025, GCN 43010; Mandarakas et al. 2025, GCN 43011; Pankov et al. 2025, GCN 43012; Bochenek et al. 2025, GCN 43015; Klinger et al. 2025, GCN 43016; Patil et al. 2025, GCN 43019; Pérez-Fournon et al. 2025, GCN 43020; Bochenek et al. 2025, GCN 43024; Busmann et al. 2025, GCN 43026; Hagio et al. 2025, GCN 43029; Bochenek et al. 2025, GCN 43038; Mo et al. 2025, GCN 43044). The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalogue. View this GCN Circular online at https://gcn.nasa.gov/circulars/43067. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41146] GRB 251209A: AstroSat CZTI detection
by GCN Circulars 10 Dec '25

10 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43066 SUBJECT: GRB 251209A: AstroSat CZTI detection DATE: 25/12/10 16:59:18 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), Harsha K. H. (IUCAA), A. Arya (IITB), A. Goyal (IITB), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long, bright GRB 251209A which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 43048). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-12-09 13:24:31.50 UTC. The measured peak count rate associated with the burst is 358 (+38, -34) counts/s above the background in the combined data of three quadrants (out of four), with a total of 5908 (+328, -277) counts. The local mean background count rate was 208 (+1, -2) counts/s. Using cumulative rates, we measure a T90 of 38 (+4, -3) s. In the preliminary analysis, we find 594 Compton events associated with this event. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-12-09 13:24:35.75 UTC. The measured peak count rate associated with the burst is 435 (+68, -32) counts/s above the background in the combined data of all quadrants, with a total of 6675 (+484, -624) counts. The local mean background count rate was 1160 (+3, -3) counts/s. We measure a T90 of 33 (+5, -3) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/43066. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41145] IceCube Alert 251210.46: Global MASTER-Net observations report
by GCN Circulars 10 Dec '25

10 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43065 SUBJECT: IceCube Alert 251210.46: Global MASTER-Net observations report DATE: 25/12/10 15:13:19 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-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the IceCube Alert 251210.46 (trigger No 43378962,02h 22m 57.84s , +20d 42m 14.4s, R=0.72) errorbox 11898 sec after notice time and 11947 sec after trigger time at 2025-12-10 14:25:22 UT, with upper limit up to 18.0 mag. Observations started at twilight. The observations began at zenith distance = 52 deg. The sun altitude is -8.9 deg. The galactic latitude b = -37 deg., longitude l = 151 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3067269 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 12008 | 2025-12-10 14:25:22 | MASTER-Kislovodsk | (02h 19m 29.66s , +20d 34m 40.7s) | P- | 120 | 13.1 | 12008 | 2025-12-10 14:25:22 | MASTER-Kislovodsk | (02h 19m 38.74s , +20d 11m 50.3s) | P| | 120 | 15.4 | 12148 | 2025-12-10 14:27:42 | MASTER-Kislovodsk | (02h 19m 29.78s , +20d 34m 42.4s) | P- | 120 | 14.5 | 12148 | 2025-12-10 14:27:42 | MASTER-Kislovodsk | (02h 19m 38.65s , +20d 11m 54.3s) | P| | 120 | 16.8 | 12288 | 2025-12-10 14:30:02 | MASTER-Kislovodsk | (02h 19m 29.78s , +20d 34m 47.8s) | P- | 120 | 15.0 | 12288 | 2025-12-10 14:30:02 | MASTER-Kislovodsk | (02h 19m 38.50s , +20d 11m 56.8s) | P| | 120 | 17.3 | 12428 | 2025-12-10 14:32:22 | MASTER-Kislovodsk | (02h 19m 29.82s , +20d 34m 52.9s) | P- | 120 | 15.3 | 12428 | 2025-12-10 14:32:22 | MASTER-Kislovodsk | (02h 19m 38.48s , +20d 12m 01.1s) | P| | 120 | 17.4 | 12568 | 2025-12-10 14:34:42 | MASTER-Kislovodsk | (02h 19m 29.68s , +20d 34m 59.2s) | P- | 120 | 15.3 | 12568 | 2025-12-10 14:34:42 | MASTER-Kislovodsk | (02h 19m 38.42s , +20d 12m 06.0s) | P| | 120 | 17.5 | 12708 | 2025-12-10 14:37:02 | MASTER-Kislovodsk | (02h 19m 29.59s , +20d 35m 05.6s) | P- | 120 | 15.5 | 12708 | 2025-12-10 14:37:02 | MASTER-Kislovodsk | (02h 19m 38.42s , +20d 12m 11.9s) | P| | 120 | 17.5 | 12848 | 2025-12-10 14:39:22 | MASTER-Kislovodsk | (02h 19m 38.40s , +20d 12m 19.1s) | P| | 120 | 17.7 | 12848 | 2025-12-10 14:39:22 | MASTER-Kislovodsk | (02h 19m 29.44s , +20d 35m 13.4s) | P- | 120 | 15.5 | 12987 | 2025-12-10 14:41:41 | MASTER-Kislovodsk | (02h 19m 38.43s , +20d 12m 25.5s) | P| | 120 | 17.7 | 12987 | 2025-12-10 14:41:41 | MASTER-Kislovodsk | (02h 19m 29.28s , +20d 35m 20.8s) | P- | 120 | 15.4 | 13128 | 2025-12-10 14:44:01 | MASTER-Kislovodsk | (02h 19m 29.39s , +20d 35m 24.2s) | P- | 120 | 15.5 | 13128 | 2025-12-10 14:44:01 | MASTER-Kislovodsk | (02h 19m 38.43s , +20d 12m 31.5s) | P| | 120 | 17.9 | 13267 | 2025-12-10 14:46:21 | MASTER-Kislovodsk | (02h 19m 38.43s , +20d 12m 39.0s) | P| | 120 | 17.9 | 13267 | 2025-12-10 14:46:21 | MASTER-Kislovodsk | (02h 19m 29.15s , +20d 35m 34.0s) | P- | 120 | 15.5 | 13407 | 2025-12-10 14:48:41 | MASTER-Kislovodsk | (02h 19m 38.45s , +20d 12m 46.7s) | P| | 120 | 17.9 | 13407 | 2025-12-10 14:48:41 | MASTER-Kislovodsk | (02h 19m 29.08s , +20d 35m 41.2s) | P- | 120 | 15.7 | 13547 | 2025-12-10 14:51:01 | MASTER-Kislovodsk | (02h 19m 38.48s , +20d 12m 54.0s) | P| | 120 | 17.9 | 13547 | 2025-12-10 14:51:01 | MASTER-Kislovodsk | (02h 19m 28.90s , +20d 35m 48.4s) | P- | 120 | 15.7 | 13687 | 2025-12-10 14:53:21 | MASTER-Kislovodsk | (02h 19m 28.84s , +20d 35m 56.4s) | P- | 120 | 15.6 | 13687 | 2025-12-10 14:53:21 | MASTER-Kislovodsk | (02h 19m 38.55s , +20d 13m 01.8s) | P| | 120 | 17.9 | 13827 | 2025-12-10 14:55:41 | MASTER-Kislovodsk | (02h 19m 28.68s , +20d 36m 03.8s) | P- | 120 | 15.8 | 13827 | 2025-12-10 14:55:41 | MASTER-Kislovodsk | (02h 19m 38.61s , +20d 13m 09.1s) | P| | 120 | 17.8 | 13967 | 2025-12-10 14:58:01 | MASTER-Kislovodsk | (02h 19m 28.52s , +20d 36m 10.3s) | P- | 120 | 15.8 | 13967 | 2025-12-10 14:58:01 | MASTER-Kislovodsk | (02h 19m 38.69s , +20d 13m 15.4s) | P| | 120 | 17.9 | 14107 | 2025-12-10 15:00:21 | MASTER-Kislovodsk | (02h 19m 38.76s , +20d 13m 21.0s) | P| | 120 | 18.0 | 14107 | 2025-12-10 15:00:21 | MASTER-Kislovodsk | (02h 19m 28.32s , +20d 36m 15.6s) | P- | 120 | 15.6 | 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/43065. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41144] IceCube-251210A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 10 Dec '25

10 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43064 SUBJECT: IceCube-251210A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/12/10 14:20:41 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-12-10 at 11:06:14.40 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_GOLD alert stream. The average astrophysical neutrino purity for Gold alerts is 50%. This alert has an estimated false alarm rate of 0.7301 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/141715_43378962.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 25-12-10 Time: 11:06:14.40 UT RA: 35.29 (+0.68/-0.69 deg 90% PSF containment) J2000 Dec: 20.34 (+0.64/-0.71 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. No known gamma-ray sources listed in the Fermi 4FGL-DR4 or 3FHL catalogs are located within the 90% uncertainty region of the event. 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/43064. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41143] EP251124a: Mondy optical upper limit
by GCN Circulars 10 Dec '25

10 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43063 SUBJECT: EP251124a: Mondy optical upper limit DATE: 25/12/10 11:55:55 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. A. Volnova (IKI), E. Klunko (ISTP), A. S. Pozanenko, N. S. Pankov (HSE, IKI) (IKI) report on behalf of IKI-GRB-FuN: We observed the field of the EP251124a triggered by EP/WXT (Zhou et al., GCN 42816; GCN 42832) with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy) taking several 120-second expositions in R-band starting on Nov.24 UT 14:36:01 in the R filter. In the error boxes reported by Zhou et al. (GCN 42816) we do not detect any new optical transient in the stacked frame. The photometry and observational details are the following: Date UT start t-T0 Exp. Filter UL Site/Telescope (mid,days) (n*s) (3sigma) 2025-11-24 14:36:01 0.16386 30*120 R 22.3 Mondy/AZT-33IK The photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction. Our upper limit is in agreement with previously reported limits (Mohan et al., GCN 42817; Wang et al., GCN 42824; Lipunov et al., GCN 42828; van Hoof et al., GCN 42829; Ma et al, GCN 42833; Gillanders et al., GCN 42862). View this GCN Circular online at https://gcn.nasa.gov/circulars/43063. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41142] GRB 251129A/EP251129a: AbAO and Mondy optical observations
by GCN Circulars 10 Dec '25

10 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43062 SUBJECT: GRB 251129A/EP251129a: AbAO and Mondy optical observations DATE: 25/12/10 09:30:07 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> N. S. Pankov (HSE, IKI), E. Klunko (ISTP), R. Ya. Inasaridze (AbAO), A. A. Volnova (IKI), A. S. Pozanenko (IKI) report on behalf of IKI-GRB-FuN: We observed the field of GRB 251129A initially detected by SVOM (Tan et al., GCN 42877) and also detected by Einstein Probe as EP251129a (Wu et al., GCN 42884) and Swift (Evans, GCN 42888; Page et al., GCN 42891). The observations were carried out with the AS-32 0.7m telescope of the Abastumani Observatory (AbAO) and the 1.5m telescope of the Sayan Solar Observatory (Mondy). The observations started on 2025-11-29 at 18:58 UT at AbAO. The optical afterglow (Angulo et al., GCN 42880; Wu et al., GCN 42882; Watson, GCN 42883; Masi, GCN 42885; Li et al., GCN 42887; Lipunov et al., GCN 42892; Moskvitin & Spiridonova, GCN 42897; Guziy et al., GCN 42899; Sanchez-Ramirez et al., GCN 42900; Yaqup et al., GCN 42942; Kuin and Cenko, GCN 42959; Xin et al., GCN 42972) is only visible in the stacked images from Mondy. The preliminary photometry and the observation properties are presented above: Date UT start t-T0 Exp. Filter OT Err. UL Site/Telescope (mid,days) (n*s) (3sigma) 2025-11-29 18:58:15 0.70255 51*60 R n/d n/d 17.6 AbAO/AS-32 2025-11-29 20:15:26 0.75928 30*120 R 21.57 0.15 22.2 Mondy/AZT-33IK 2025-11-30 19:50:56 1.75199 44*120 R 21.47 0.13 22.2 Mondy/AZT-33IK The photometry is based on nearby stars from the USNO-B1 catalog (R2 magnitudes) and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43062. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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