TITLE: GCN CIRCULAR NUMBER: 39936 SUBJECT: GRB250328A: A fading optical afterglow confirmed by SVOM/VT DATE: 25/03/30 03:36:32 GMT FROM: SVOM_group svomgroup@bao.ac.cn
H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, J. Wang, W. J. Xie, B.T. Wang (YNAO, CAS), Z. H. Yao, Y. N. Ma, Y. Xu, P. P. Zhang, X. H. Han, Y. J. Xiao, H. B. Cai, J. Y. Wei (NAOC)，M. Brunet, J. Malzac (IRAP) report on behalf of the SVOM team:
SVOM/VT performed a second ToO observation on the burst triggered by SVOM/ECLAIRs (Brunet et al., GCN 39910). The observation began from about 20.65 hours to 21.5 hours after the burst in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
The candidate reported (Schneider et al., GCN 39919, Schneider et al., GCN 39920) was fading by about one magnitude in stack images in both channels, compared to the previous brightness reported by Li et al. GCN 39923. The magnitude is VT_R = 22.8+/-0.2 mag(AB) at the mid time of 21.05 hours after the burst. The photometry has not been corrected for the Galactic extinction.
We proposed that this candidate is the optical counterpart of GRB 250328A.
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.
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