GCN Circular 41399

F. Magnani (CPPM), D. Dornic (CPPM), O. Godet (IRAP), H. Goto (Kanazawa Univ.) report on behalf of the SVOM mission team:

At 2025-08-16T15:31:20 UTC (T0), SVOM/ECLAIRs triggered and located a likely X-ray transient (SVOM burst-id sb25081602).

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 Count-Rate Trigger (CRT), which produced a sequence of 3 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 9.53 in the [5-20] keV energy band over a time window of 20.40 seconds starting at 2025-08-16T15:31:10.

The localization of the best alert is R.A., Dec. 78.514, -39.982 degrees:
R.A. (J2000) = 5h14m03.43s
Dec. (J2000) = -39d58m56.04s
 with a 90% confidence level (C.L.) radius of 8.33 arcmin (including systematic error of 2 arcmin added in quadrature).

The LMXB 4U 0513-40 is located at 3.75 arcmin from the ECLAIRs position. We note that there are other X-ray sources within the ECLAIRs error circle.  

SVOM did not slew.

No X-ray observation could be performed by SVOM/MXT for the time being. No optical observation could be performed by SVOM/VT for the time being.

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 F. Magnani (francesco.magnani.work@gmail.com).
Please contact the BA by email if you require additional information.