TITLE:   GCN CIRCULAR
NUMBER:  45642
SUBJECT: EP260917a: SVOM/VT optical upper limits
DATE:    26/09/19 09:03:02 GMT
FROM:    Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>

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

SVOM/VT performed ToO observation on the field of EP260917a (Huang et al., GCN 45621). The observation started at 2026-09-18T03:23:30 UTC, 17.8 hours after trigger in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
 
No credible uncatalogued candidates were identified in our stacked images within the error box of EP-WXT (Huang et al., GCN 45621) compared to the Legacy Survey. 

The following measurements are in the AB magnitude and are not corrected for Galactic extinction:

Mid time | Band | Exposure Time |  5-sigma upper limit
18.0  hr    VT_B     23*50  sec     > 22.8 mag    
18.0  hr    VT_R     23*50  sec     > 22.7 mag
 
Our results are consistent with the non-detections from COLIBRÍ (Guelfand et al., GCN 45624) and WINTER (Mohan et al., GCN 45628).

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.