TITLE:   GCN CIRCULAR
NUMBER:  43337
SUBJECT: EP260105a: SVOM/VT optical upperlimit
DATE:    26/01/06 03:03:52 GMT
FROM:    Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>

H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Y. N. Ma, Z. H. Yao, Y. Xu, X. H. Han, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA)   report on behalf of the SVOM/VT team.

SVOM/VT performed ToO observation on the fast X-ray transient  EP260105a (Zhou et al., GCN 43327). The observation started on 2026-01-05T07:51:04 UT (i.e. 2.06 hour post trigger) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. 

Inside the error box of the EP-FXT (Zhou et al., GCN 43333) we did not detect any new uncatalogued source, which was consistent with the non detections reported by MASTER-Net (Lipunov et al., GCN 43328) and LCO (Corcoran et al., GCN 43332). The 3 sigma limit magnitudes are derived as below:

Mid time  | Band | Exposure Time | 3 sigma limit magnitude
4.68 hour   VT_B    30*100 sec     > 23.5 mag    
4.68 hour   VT_R    30*100 sec     > 23.5 mag


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.