TITLE: GCN CIRCULAR NUMBER: 42060 SUBJECT: GRB 251002A: SVOM detection of a burst DATE: 25/10/02 20:43:05 GMT FROM: SVOM_group svomgroup@bao.ac.cn
A. Saccardi (CEA/Irfu), D. Gotz (CEA/Irfu), S. Schanne (CEA/Irfu), M. G. Bernardini (INAF & LUPM), N. Dagoneau (CEA/Irfu), P. Maggi (ObAS), report on behalf of the SVOM mission team:
At 2025-10-02T20:14:54 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 251002A (SVOM burst-id sb25100211).
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 15 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 22.39 in the [8-120] keV energy band over a time window of 10.20 seconds starting at 2025-10-02T20:14:49. The SVOM/ECLAIRs light curve showed a multiple peak structure with a T90 duration of 11.7 (+2.6/-1.5) s.
The localization of the best alert is R.A., Dec. 13.9059, -5.5440 degrees (J2000) with a 90% confidence level (C.L.) radius of 3.98 arcmin (including systematic error of 2 arcmin added in quadrature).
This burst also triggered SVOM/GRM at 2025-10-02T20:14:52 with an SNR of 10.40.
SVOM slewed to the burst.
SVOM/MXT began observing the field at 2025-10-02T20:17:42 UTC, 168 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 13.9179, -5.5679 degrees: R.A. (J2000) = 0h55m40s Dec. (J2000) = -5d34m04s with a 90% C.L. radius of 81 arcseconds.
This location is 1.60 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 Andrea Saccardi: andrea.saccardi@cea.fr. Please contact the BA by email if you require additional information.
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