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

[vsnet-grb-info 40514] IceCube-251025A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 25 Oct '25

25 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42436 SUBJECT: IceCube-251025A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/10/25 14:59:09 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-10-25 at 13:47:53.26 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 2.3507 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/141518_18513107.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 25-10-25 Time: 13:47:53.26 UT RA: 145.63 (+0.88/-0.88 deg 90% PSF containment) J2000 Dec: 15.06 (+0.65/-0.62 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/42436. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40513] GRB 251025A (sb25102501): Likely a stellar flare by SVOM/VT
by GCN Circulars 25 Oct '25

25 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42435 SUBJECT: GRB 251025A (sb25102501): Likely a stellar flare by SVOM/VT DATE: 25/10/25 14:20:12 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, Y. N. Ma, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, J. R. Xu, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), Z. M. Wang (BNU), W. J. Tan (IHEP) report on behalf of the SVOM/VT team. SVOM/VT performed an automatic slew on the faint burst triggered by SVOM/ECLAIRs (sb25102501, Wang et al., GCN 42432). SVOM/VT began observing the field automatically on 2025-10-25T09:42:07, i.e., 405 sec with the slew of the platform triggered on-board, in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With X band downlinked data, we find that the high proper motion star RX J2350.0+2659 was fading with the color from blue to red. It is located with a distance of 1.4 arcminutes from SVOM/MXT position (Wang et al., GCN 42432). The brightness was fading from 10.0 mag to 12.5 mag in VT_B during the first 1.6 hour after the trigger. The position of the source is consistent with XRT Source 1 (https://www.swift.ac.uk/SVOM/SVOM_FIELD00043/). Given the fading behavior in optical and the consistency in position between VT and XRT, we propose that this event was due to a stellar flare. Our photometry was estimated in AB magnitude. 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/42435. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40512] GRB 251025A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
by GCN Circulars 25 Oct '25

25 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42434 SUBJECT: GRB 251025A: SVOM/COLIBRÍ (FM-GFT) optical upper limit DATE: 25/10/25 11:45:44 GMT FROM: nikos.mandarakas(a)lam.fr Nikos Mandarakas (LAM), Margarita Pereyra (UNAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), 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), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Z.M. Wang (BNU), W.J. Tan (IHEP): We imaged the field of the SVOM GRB 251025A (Wang et al., GCN Circ. 42432) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-10-25 09:58 to 11:00 UTC (from 0.39 to 1.41 hours after the trigger) and obtained 47 minutes of simultaneous exposure in the r and z filters. The data were analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked images, we do not detect any new source within the MXT localization region (Wang et al., GCN Circ. 42432) down to the following 5-sigma limits: r > 22.9 z > 21.7 These upper limits are consistent with the one reported by Wu et al. (GCN Circ. 42433). 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/42434. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40511] GRB 251025A: SVOM/VT VHF optical upper limit
by GCN Circulars 25 Oct '25

25 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42433 SUBJECT: GRB 251025A: SVOM/VT VHF optical upper limit DATE: 25/10/25 11:14:50 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> C. Wu, H. L. Li, L. P. Xin, Y. L. Qiu (NAOC), J. Palmerio (CEA), Z. M. Wang (BNU), W. J. Tan (IHEP) report on behalf of the SVOM/VT team. SVOM/VT began observing the field of GRB 251025A (Wang et al., GCN 42432) at 202025-10-25T09:43:10 UT, 7.8 minutes after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. No optical candidate was detected within the position of MXT (Wang et al., GCN 42432), based on a preliminary analysis of the source list and 1-bit subimage downloaded via VHF network. The 3 sigma upper limits are about 21.5 mag in VT_R with an effective exposure time of 6*50 sec at 10.3 min post trigger. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/42433. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40510] GRB 251025A: SVOM detection of a faint burst
by GCN Circulars 25 Oct '25

25 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42432 SUBJECT: GRB 251025A: SVOM detection of a faint burst DATE: 25/10/25 10:15:26 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Z.M. Wang (BNU), W.J. Tan (IHEP), D. Turpin (CEA), B. Cordier(CEA), M. Moita (CEA), U. Jacob (LUPM) , report on behalf of the SVOM mission team: At 2025-10-25T09:35:22 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 251025A (SVOM burst-id sb25102501). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Image Trigger (IMT), which produced a sequence of 4 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 8.01 in the [5-20] keV energy band over a time window of 327.68 seconds starting at 2025-10-25T09:32:38. The localization of the best alert is R.A., Dec. 357.5739, 27.0002 degrees (J2000) with a 90% confidence level (C.L.) radius of 9.82 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM slewed to the burst. SVOM/MXT began observing the field at 2025-10-25T09:41:11 UTC, 349 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 357.5530, 26.9869 degrees: R.A. (J2000) = 23h50m12.72s Dec. (J2000) = 26d59m12.90s with a 90% C.L. radius of 25.08 arcseconds. This location is 1.37 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received. VT began observing the field after the slew. The analysis of the data will be published in a future circular. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Ziming Wang: zmwang489(a)mail.bnu.edu.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/42432. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40509] GRB 251003A: VLA Detection
by GCN Circulars 24 Oct '25

24 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42431 SUBJECT: GRB 251003A: VLA Detection DATE: 25/10/24 22:49:01 GMT FROM: Sarah Chastain at University of New Mexico <sarahichastain(a)gmail.com> S. I. Chastain (TTU) and A. J. van der Horst (GWU) report: We carried out follow up observations of GRB 251003A, detected by Fermi (Fermi GBM Team, GCN 42069) and Swift (Beardmore et al., GCN 42070) with the Karl G. Jansky Very Large Array. At 18 days post-burst (2025-10-21 06:04:43.725), we significantly detect the afterglow at 9 GHz at 40 +/- 5 microJy/beam at the location: RA (J2000): 1:14:07.092 ± 0.003 seconds Dec (J2000): 56:29:27.94 ± 0.05 arcseconds These observations were taken as part of the Fermi GI project SF181025. We thank the VLA staff for scheduling and executing these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42431. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40508] GRB 251024A: Enhanced Swift-XRT position
by GCN Circulars 24 Oct '25

24 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42430 SUBJECT: GRB 251024A: Enhanced Swift-XRT position DATE: 25/10/24 21:38:35 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 1910 s of XRT Photon Counting mode data and 3 UVOT images for GRB 251024A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 306.59782, -68.57239 which is equivalent to: RA (J2000): 20h 26m 23.48s Dec (J2000): -68d 34' 20.6" with an uncertainty of 2.2 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at https://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42430. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40507] GRB 251023C: Glowbug gamma-ray detection
by GCN Circulars 24 Oct '25

24 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42429 SUBJECT: GRB 251023C: Glowbug gamma-ray detection DATE: 25/10/24 21:38:04 GMT FROM: richard.s.woolf.civ(a)us.navy.mil R. Woolf, C.C. Cheung, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 251023C, which was also detected by Swift/BAT-GUANO (GCN 42412), CALET (GCN 42414), and AstroSat CZTI (GCN 42419). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-10-23 16:24:17.240 with a duration of 30.7 s and a total significance of about 110 sigma. The light curve comprises two primary peaks at ~T0+10s and ~T0+14s, and a tertiary peak around ~T0+28s. The Glowbug onset is ~7.7 s earlier than the CALET-reported T0 because we detect low-level emission prior to the first peak at ~T0+10s. The best-fit localization is RA, Decl. (J2000, deg) = 333.9, 58.4 with a radius of 2.1 deg (95% confidence), with a highly uncertain systematic uncertainty. We note that this localization is offset by ~40 deg from the Swift/BAT-GUANO-reported localization. The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS, and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/42429. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40506] GRB 251024A: LCOGT Optical Afterglow Detection
by GCN Circulars 24 Oct '25

24 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42428 SUBJECT: GRB 251024A: LCOGT Optical Afterglow Detection DATE: 25/10/24 19:07:28 GMT FROM: Robert Strausbaugh at Eastern Illinois University <rstrausbaugh(a)eiu.edu> R. Strausbaugh (Eastern Illinois University), A. Cucchiara (NASA) report on behalf of a larger collaboration: We observed the Swift GRB 251024A field (Moss et al., GCN 42426) with the LCOGT 1-meter Sinistro instrument at the South African Astronomical Observatory site, on October 24, from 18:18 to 18:50 UT (corresponding to 0.51 to 1.05 hours after the GRB trigger time) with the Bessel I and R filters. We performed a series of 3x300s exposures in I-band and R-band. We detect an uncatalogued source in the XRT error region in both bands, which we propose to be the afterglow. The following magnitudes are calculated using the USNO-B1.0 catalog as reference: R = 21.2 +/- 0.1 I = 21.2 +/- 0.2 These magnitudes are not corrected for galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42428. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40505] GRB 251022A: KAIT optical observations
by GCN Circulars 24 Oct '25

24 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42427 SUBJECT: GRB 251022A: KAIT optical observations DATE: 25/10/24 18:47:18 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of GRB 251022A (Fermi GBM Team, GCN 42380; Di Lalla et al., GCN 42384; DeLaunay et al., GCN 42409; Mukherjee et al., GCN 42410) starting at ~0.46d and again at ~1.39d after the burst. A set of clear (roughly R) filter images were obtained. We detected the optical afterglow (O’Neill et al. GCN 42386; Becerra et al. GCN 42394; Lipunov et al. GCN 42395; Mandarakas et al. GCN 42397; Mohan et al. GCN 42413; Méndez et al., GCN 42423) in our coadd images. We estimate the afterglow to be 19.2 +/- 0.2 and 21.6 +/- 0.3 mag (Vega) at a mid time of ~0.47d and ~1.40d respectively. View this GCN Circular online at https://gcn.nasa.gov/circulars/42427. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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