TITLE: GCN CIRCULAR NUMBER: 39701 SUBJECT: EP250304a: SVOM/VT optical observation DATE: 25/03/13 08:06:28 GMT FROM: SVOM_group svomgroup@bao.ac.cn
R. C. Chen (NJU), L. Lan (NAOC), C. W. Wang, W. J. Tan (IHEP), L. P. Xin, Y. L. Qiu, H. L. Li, Z. H. Yao, Y. Xu, P. P. Zhang, W. J. Xie, J. Wang, X. H. Han, Y. J. Xiao, H. B. Cai, J. Y. Wei (NAOC), J. T. Palmerio (CEA/Irfu) report on behalf of the SVOM mission team.
SVOM/VT conducted ToO follow-up observations of the X-ray transient EP250304a (Chen et al., GCN 39580) at the location of Swift-XRT (Page et al., GCN 39584) and Swift/UVOT (Shilling et al., GCN 39587) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously.
The optical counterpart of EP250304a (Trigger ID: 01709132237, Chen et al., GCN 39580; Liu et al., GCN 39583; Saccardi et al., GCN 39585; Shilling et al., GCN 39587) was clearly detected in VT_R and VT_B images.
The brightness in AB magnitude was estimated to be:
Mid time UTC | Band | Magnitude | Magnitude error 2025-03-08T14:31:28.502 | VT_B | 21.59 | 0.07 2025-03-08T14:31:28.502 | VT_R | 21.60 | 0.10 2025-03-05T10:27:01.518 | VT_B | 21.35 | 0.06 2025-03-05T10:27:01.518 | VT_R | 21.59 | 0.10
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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