GCN Circular 40147

Z. Wang (GXU), W. Zheng (UCB), S. Schanne (CEA), M.-G. Bernardini (INAF/LUPM) report on behalf of the SVOM mission team:

SVOM/ECLAIRs triggered on the X-ray transient labelled sb25041603 (SVOM burst-id sb25041603) starting at 2025-04-16T06:28:04 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 1 alert with the signal-to-noise-ratio (SNR) of 7.25 in the 5-8 keV energy band over a time window of 655.36 seconds starting at Tb.

The localization of the best alert is R.A., Dec 184.1075, 52.6309 degrees:

RA (J2000) = 12h16m25.81s
Dec (J2000) = 52d37m51.11s

with a 90% C.L. radius of 10.81 arcmin (including systematic error of 2 arcmin added in quadrature).

We notice the presence of several X-ray transient candidate sources in this error-box, among which the cataclismic variable V* EG UMa located at 9.3 arcmin, but also several quasars, the closest one being 2MASS J12161363+5242459 located at 5.3 arcmin.

The detection significance was below the Slew threshold, so no immediate slew was performed on this burst.

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 Ziqi Wang (zq.wang@st.gxu.edu.cn).
Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.