TITLE: GCN CIRCULAR NUMBER: 40283 SUBJECT: EP250428b: SVOM/VT upper limit DATE: 25/04/30 01:39:45 GMT FROM: Liping Xin at NAOC, SVOM xlp@nao.cas.cn
L. P. Xin, Y. L. Qiu, H. L. Li, C. Wu, Z. H. Yao(NAOC), M. J. Liu, Q. Y. Wu, T. Zhao, Y. J. Song (NAO, CAS), H. Z. Wu (HUST), C. C. Jin (NAO, CAS), X. H. Han,Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC) report on behalf of the SVOM team and the Einstein Probe (EP) team:
SVOM/VT conducted ToO follow-up observations of the EP250428b(Liu et al., GCN 40277). The observation started on 2025-04-29T17:26:22 UT, 2025 Apr 29, in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously.
With the effective exposure time of 2500 seconds, no any new sources were detected in EP/FXT error box (Liu et al., GCN 40277) in stacked images with the 3 sigma upper limit of VT_B=23.2 mag and VT_R=23.0 mag, compared to Legacy survey, at the mid time of 1.487 days after the transient time.
This result is consistent with the reports (Konno et al., GCN 40281, Moskvitin et al., GCN 40282).
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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