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[vsnet-grb-info 40540] GRB 251026A: SVOM/C-GFT upper limit
by GCN Circulars 26 Oct '25

26 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42458 SUBJECT: GRB 251026A: SVOM/C-GFT upper limit DATE: 25/10/26 14:04:34 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Chao WU (NAOC), Zhe Kang (CHO), Liping Xin(NAOC), Xuhui Han(NAOC), Pinpin Zhang (NAOC), Xiaomeng Lu (NAOC), Zhenwei Li (CHO), You Lv (CHO), Ruosong Zhang (NAOC), Yujie Xiao(NAOC), Yulei Qiu(NAOC), Jing Wang (NAOC), Jinsong Deng(NAOC), Lei Huang(NAOC), Jianyan Wei (NAOC), J.X Cao (GXU), X. Tian (GXU) report on behalf of the SVOM/C-GFT team: We observed the field of GRB 251026A (sb25102605) detected by SVOM/ECLAIRs (Cao et al., GCN 42454) with LATIOS on SVOM/C-GFT. Observations started at 2025-10-26T10:31:43 UTC, ~2.07 hr after the trig-ger. A series of g, r, and i band images were obtained. No credible candidate was detected within the error box provided by SVOM/MXT (Cao et al., GCN 42454) in our stacked images. The corresponding three sigma upper limit is, mag_i=19.65 at the midpoint of the observations, T₀ + 2.15 hr. The photometry was calibrated against nearby Pan-STARRS1 stars and no correction for Galactic dust extinction was applied. This result is consistent with Postigo et al. (GCN 42456). We thank the observation assistants Bowen Li and Hongxu Xuan at Jilin observatory for their excellent support. The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching. View this GCN Circular online at https://gcn.nasa.gov/circulars/42458. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40539] IceCube-251025A: DDOTI Optical Upper Limit
by GCN Circulars 26 Oct '25

26 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42457 SUBJECT: IceCube-251025A: DDOTI Optical Upper Limit DATE: 25/10/26 13:42:49 GMT FROM: Rosa Leticia Becerra Godínez at Instituto de Astronomía, UNAM <rbecerra(a)astro.unam.mx> Rosa L. Becerra (UNAM), Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Nat Butler (ASU), Simone Dichiara (Penn State University), 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-251025A (bronze) event (IceCube Collaboration, GCN Circ. 42436) 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 2025-10-26 UTC. DDOTI observed from 10:41 UTC to 12:41 UTC (T+20.9 h to T+22.9 h after the trigger), with a total exposure time of 24 minutes, covering the entire error region reported by IceCube (IceCube Collaboration, GCN Circ. 42436). These observations were interleaved with other scientific programs. Comparing our observations to the USNO-B1 and PanSTARRS PS1 DR2 catalogues, we detect no uncatalogued sources within the observed field to a 10-sigma limiting AB magnitude of: w > 20.0. 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/42457. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40538] GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
by GCN Circulars 26 Oct '25

26 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42456 SUBJECT: GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit DATE: 25/10/26 11:16:33 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo(a)gmail.com> Antonio de Ugarte Postigo (LAM), Margarita Pereyra (UNAM), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (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), 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), J.X Cao (GXU), X. Tian (GXU): We imaged the field of the SVOM GRB 251026A (Cao et al., GCN Circ. 42454) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-10-26 08:49:51 to 09:08:59 UTC (from 22.5 to 41.6 minutes after the trigger) and obtained 16x60 seconds of exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ pipeline and analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1/SkyMapper catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we do not detect any new source within the MXT source position (Cao et al., GCN Circ. 42454) down to the following 5-sigma limit: r > 23.0 mag z > 21.6 mag Further observations are ongoing. 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/42456. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40537] GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
by GCN Circulars 26 Oct '25

26 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42456 SUBJECT: GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit DATE: 25/10/26 11:16:33 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo(a)gmail.com> Antonio de Ugarte Postigo (LAM), Margarita Pereyra (UNAM), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (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), 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), J.X Cao (GXU), X. Tian (GXU): We imaged the field of the SVOM GRB 251026A (Cao et al., GCN Circ. 42454) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-10-26 08:49:51 to 09:08:59 UTC (from 22.5 to 41.6 minutes after the trigger) and obtained 16x60 seconds of exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ pipeline and analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1/SkyMapper catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we do not detect any new source within the MXT source position (Cao et al., GCN Circ. 42454) down to the following 5-sigma limit: r > 23.0 mag z > 21.6 mag Further observations are ongoing. 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/42456. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40536] GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
by GCN Circulars 26 Oct '25

26 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42456 SUBJECT: GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit DATE: 25/10/26 11:16:33 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo(a)gmail.com> Antonio de Ugarte Postigo (LAM), Margarita Pereyra (UNAM), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (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), 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), J.X Cao (GXU), X. Tian (GXU): We imaged the field of the SVOM GRB 251026A (Cao et al., GCN Circ. 42454) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-10-26 08:49:51 to 09:08:59 UTC (from 22.5 to 41.6 minutes after the trigger) and obtained 16x60 seconds of exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ pipeline and analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1/SkyMapper catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we do not detect any new source within the MXT source position (Cao et al., GCN Circ. 42454) down to the following 5-sigma limit: r > 23.0 mag z > 21.6 mag Further observations are ongoing. 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/42456. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40535] GRB 251026B: Fermi GBM Final Localization
by GCN Circulars 26 Oct '25

26 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42455 SUBJECT: GRB 251026B: Fermi GBM Final Localization DATE: 25/10/26 09:48:27 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> The Fermi GBM team reports the detection of a likely SHORT GRB "At 07:18:53.33 UT on 26 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251026B (trigger 783155938/251026305). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 132.32, Dec = -12.21 (J2000 degrees, equivalent to J2000 8h 49m, -12d 12'), with a statistical uncertainty of 8.04 degrees. The angle from the Fermi LAT boresight is 19 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251026305/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251026305/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251026305/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/42455. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40534] GRB 251026A: SVOM detection of a long burst
by GCN Circulars 26 Oct '25

26 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42454 SUBJECT: GRB 251026A: SVOM detection of a long burst DATE: 25/10/26 09:04:48 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> J.X Cao (GXU), X. Tian (GXU), J-L. Atteia (IRAP), W.J Xie (NAOC), F. Lacreu (IAP), M. Moita (CEA), report on behalf of the SVOM mission team: At 2025-10-26T08:27:22 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 251026A (SVOM burst-id sb25102605). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 11 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 11.73 in the [8-120] keV energy band over a time window of 81.92 seconds starting at 2025-10-26T08:26:46. The localization of the best alert is R.A., Dec. 72.5819, 51.8058 degrees (J2000) with a 90% confidence level (C.L.) radius of 6.86 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM slewed to the burst. SVOM/MXT began observing the field at 2025-10-26T08:31:19 UTC, 237 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 72.707, 51.776 degrees: R.A. (J2000) = 04h50m49s Dec. (J2000) = 51d46m32s with a 90% C.L. radius of 65 arcseconds. This location is 5.17 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 Jiaxin Cao: cjx(a)st.gxu.edu.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/42454. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40533] GRB 251025B: SVOM/VT optical bump
by GCN Circulars 25 Oct '25

25 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42453 SUBJECT: GRB 251025B: SVOM/VT optical bump DATE: 25/10/26 04:30:16 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H.L. Li, L.P. Xin, Y.L. Qiu, C. Wu, Y.N. Ma, Z.H. Yao, X.H. Han, J. Wang, H.B. Cai, W.J. Xie, Y. Xu, J.R. Xu, P.P. Zhang, Y.J. Xiao, J.S. Deng, J.Y. Wei (NAOC), J. Palmerio (CEA), J.X. Cao, X. Tian (GXU), S. Hussein (IJCLab), M. Brunet (IRAP) report on behalf of the SVOM team. SVOM performed an automatic slew on the burst GRB 251025B triggered by SVOM/ECLAIRs (Julakanti et al., GCN 42437) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The observation began at 2025-10-25T14:26:52, i.e., 167 sec post trigger. The optical counterpart (Wu et al., GCN 42438, 42440; Budnev et al., GCN 42439; Mohan et al., GCN 42447; Fung et al., GCN 42450) consistent with the location of Swfit-XRT (Beardmore et al., GCN 42445) was clearly detected in both VT channels. The brightness was decaying with a slope of -0.7 before 3000 sec post trigger, followed by a bump with the peak of VT_R~19.59+/-0.05 mag and VT_B~19.95+/-0.05 mag at the mid time of 5.24 hours post trigger. Our photometry was estimated in AB magnitude, and not corrected for Galactic extinction. More follow-up for this burst is encouraged. 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/42453. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40532] GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
by GCN Circulars 25 Oct '25

25 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42452 SUBJECT: GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart DATE: 25/10/26 04:18:33 GMT FROM: Margarita Pereyra Talamantes at IA-UNAM Ensenada <mpereyra(a)astro.unam.mx> Margarita Pereyra (UNAM), Antonio de Ugarte Postigo (LAM), Benjamin Schneider (LAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Camila Angulo (UNAM), 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), Diego López-Cámara (UNAM), Kin Ocelotl López (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), and S. Hussein (IJCLab) report: We imaged the field of the SVOM GRB 251025B (Hussein et al., GCN Circ. 42437) using the DDRAGO two-channel wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-10-26 02:54 to 03:17 (12.51 to 12.89 hours after the trigger) and obtained 6, 5, 5, and 16 minutes exposure in the the g, r, i, and z filters. The images were analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS catalog, is in the AB system, and is not corrected for Galactic extinction. We detect the optical counterpart (Wu et al., GCN Circ. 42438; Gress et al., GCN Circ. 42439; Wu et al., GCN Circ. 42440; Beardmore et al., GCN Circ. 42445; Mohan et al., GCN Circ. 42447; Hernández Funget al., GCN Circ. 42450) with preliminary magnitudes of: g = 20.58 +/- 0.03 r = 20.20 +/- 0.03 i = 19.90 +/- 0.04 z = 19.79 +/- 0.04 We note that the afterglow appears to be brighter in r in our observations at about 12 hours than it was in the observations of Mohan et al. (GCN Circ. 42447) at about 2 hours, suggesting a very strong rebrightening. We further note a possible host galaxy candidate at the afterglow position in the Legacy Survey with r ≈ 23.3 and a photometric redshift if z ≈ 0.98 +/- 0.19. This is consistent with the detection in g. Further observations and analysis are ongoing. 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/42452. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40531] GRB 251023A: SVOM/GRM observation
by GCN Circulars 25 Oct '25

25 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42451 SUBJECT: GRB 251023A: SVOM/GRM observation DATE: 25/10/26 03:54:05 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Zheng-Hang Yu, Wen-Jun Tan, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Feliu Lacreu (IAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a burst GRB 251023A (SVOM trigger reference: sb25102301) at 2025-10-23T05:57:44.000 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN#42385) and Glowbug (R. Woolf, GCN#42408). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple peaks with a T90 of 63.5 +19.5/-5.5 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251023A.png In addition, the position of this burst, as determined by Fermi/GBM (RA= 39.87, DEC= -6.53, GCN#42385), is located at about 51 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-2 to T0+70 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.45 +0.25/-0.26 and the cutoff energy, parameterized as Epeak, is 143 +26/-19 keV. The event fluence (10-1000 keV) in this time interval is (5.47 +0.55/-0.56)E-6 erg/cm^2. The localization of GRB 251023A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb251023A_amati.png 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/42451. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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