TITLE: GCN CIRCULAR NUMBER: 39445 SUBJECT: EP250223a: SVOM/VT optical observation DATE: 25/02/24 07:51:36 GMT FROM: SVOM_group svomgroup@bao.ac.cn

L.P. Xin, Y.L. Qiu(NAOC), Y. Wang(PMO),H.L. Li, C. Wu, Z.H. Yao, Y. N. Ma, X.H. Han, H.B. Cai, J. Wang, Y. Xu, J.Y. Wei(NAOC), J. T. Palmerio(CEA/Irfu) report on behalf of the SVOM team:

The SVOM/VT conducted a ToO follow-up observations of the EP250223a (Lian et al., GCN 39429) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously.

The afterglow(Benjamin et al., GCN 39436) was clearly detected within the errorbox of EP/FXT (Lian et al., GCN 39429) in VT_R and VT_B images.

The afterglow was fading during our observations and the brightness was estimated to be 19.21+/-0.05 mag in AB magnitude in VT_R, and 20.11+/-0.05 mag in AB magnitude in VT_B, at the mid time of 3.7 hours post the burst.

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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