TITLE: GCN CIRCULAR NUMBER: 39957 SUBJECT: GRB 250330A: SVOM/VT optical upper limit DATE: 25/03/31 04:35:08 GMT FROM: SVOM_group svomgroup@bao.ac.cn
Z.M. Wang, A. Li (BNU), L.P. Xin, H.L. Li, Y. L. Qiu, C. Wu, Z.H. Yao, Y. Xu, P.P. Zhang, J. Wang, Y.N. Ma, X.H. Han, H.B. Cai, J.Y. Wei(NAOC) report on behalf of the SVOM/VT team:
SVOM performed two Target of Opportunity observations of GRB 250330A (Cenko et al., GCN 39938; Pathak, GCN 39944; Osborne et al., GCN 39947) in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously， starting at 2025-03-30T09:17:44 UT, and 2025-03-30T12:40:58 UT, respectively.
No sources were detected in the stacked images within the XRT source position (Page, GCN 39940).
The 3 sigma limits in VT_R is 21.7 mag (AB) with the exposure time of 3 x 100s at the medium time of 3.2 hours after the Swift BAT trigger, and 23.0 mag with the exposure of 12*120s, at the medium time of 6.8 hours after the burst.
This result is consistent with the reports (Becerra, GCN 39941; Siegel et al., GCN 39948; Perez-Garcia et al., GCN 39949; Lipunov et al., GCN 39950).
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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