GCN Circular 42433
Subject
GRB 251025A: SVOM/VT VHF optical upper limit
Event
Date
2025-10-25T11:14:50Z (2 days ago)
From
Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Via
Web form
C. Wu, H. L. Li, L. P. Xin, Y. L. Qiu (NAOC), J. Palmerio (CEA), Z. M. Wang (BNU), W. J. Tan (IHEP) report on behalf of the SVOM/VT team.
SVOM/VT began observing the field of GRB 251025A (Wang et al., GCN 42432) at 202025-10-25T09:43:10 UT, 7.8 minutes after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
No optical candidate was detected within the position of MXT (Wang et al., GCN 42432), based on a preliminary analysis of the source list and 1-bit subimage downloaded via VHF network. The 3 sigma upper limits are about 21.5 mag in VT_R with an effective exposure time of 6*50 sec at 10.3 min post trigger.
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/VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.