GCN Circular 41654
Subject
GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
Event
Date
2025-09-02T07:31:25Z (11 days ago)
From
Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Via
Web form
H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, Z. H. Yao, Y. N. Ma, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team.
SVOM performed an automatic slew on the soft burst triggered by SVOM/ECLAIRs (Xie et al., GCN 41614). SVOM/VT began observing the field automatically on 2025-08-31T09:34:43, i.e., 335 sec with the slew of the platform triggered on-board, in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
With X band downlinked data, we find that the position of the high proper motion star G 272-61 is consistent with XRT Source 1 (Evans et al., GCN 41617). With a refined analysis, it was decreasing in brightness from 7.6 mag to 10.0 mag in VT_B during the first 0.5 hour after the trigger time, confirming this event as due to a stellar flare. Our photometry was estimated in AB magnitude.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.