GCN Circular 40358

Chenwei Wang (IHEP), Lin LAN, Wenjin XIE, Donghua ZHAO (NAOC), Li ZHANG (IHEP), Pierre MAGGI (ObAS) on behalf of the SVOM mission team.


SVOM/ECLAIRs triggered and located GRB 250506A (SVOM burst-id sb25050601) at 2025-05-06T02:23:24.501UTC. 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 1 alerts. CRT provided the alert with the best signal-to-noise-ratio (SNR) of 12.51 in the [8-120] keV energy band over a time window of 2.50 seconds starting at 2025-05-06T02:23:22.001

The localization of the best alert is R.A., Dec. 219.61, 29.28 degrees:
R.A. (J2000) = 14h38m27.02s
Dec. (J2000) = 29d16m38.09s
with a 90% confidence level (C.L.) radius of 6.47 arcmin (including systematic error of 2 arcmin added in quadrature).

This burst also triggered SVOM/GRM with 3 GRDs but only the first pulse is detected, since the other part is in occultation. The lightcurve of GRM could be found in the link below:
https://www.bursthub.cn//admin/static/svgrb250506A.png

SVOM slewed to the burst. It was occulted by the Earth at the time of the alert, thus neither MXT nor VT data are available for the early time.

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 Chenw ei Wang: cwwang@ihep.ac.cn.
Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.