GCN Circular 39850

Ziming Wang (BNU), Yifang Liang (PMO), An Li (BNU), Wenjin Xie, Donghua Zhao (NAOC), Stephane Schanne, Nicolas Dagoneau (CEA)

Report on behalf of the SVOM mission team.

SVOM/ECLAIRs triggered and located a soft X-ray transient source (SVOM burst-id sb25032302) starting at 2025-03-23T04:08:21 UTC (Tb).

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 1 alert with the signal-to-noise-ratio (SNR) of 7.90 in the 5-8 keV energy band over a time window of 1310.72 seconds starting at Tb.

The localization of the best alert is R.A., Dec 194.8370, 28.0383 degrees:
RA (J2000) = 12h59m20.87s
Dec (J2000) = 28d02m17.90s
with a 90% C.L. radius of 9.95 arcmin (including systematic error of 2 arcmin added in quadrature).

We notice that this error-box overlaps with the Coma cluster containing several X-ray sources which could produce such a transient. 

This trigger did not reach the slew threshold, hence no automatic slew was performed. 

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.

The Burst Advocate (BA) on shift for this burst is Ziming Wang (202421101144@mail.bnu.edu.cn). 
Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.