TITLE:   GCN CIRCULAR
NUMBER:  36206
SUBJECT: EP240420a:  GWAC-F50A optical upper limit
DATE:    24/04/21 07:47:22 GMT
FROM:    Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>

L. P. Xin(NAOC), Y. G. Yang(HNU), C. WU(NAOC), Y. L. Qiu(NAOC), J. Wang(GXU/NAOC),    

H. L. Li(NAOC),  C. Wu(NAOC),  E. W. Liang(GXU), X. H. Han(NAOC), X. M. Lu(NAOC),   

R. S. Zhang(NAOC), Y. Xu(NAOC), Y.J . Xiao(NAOC), P. P. Zhang(NAOC), L. Lan(NAOC),   

J. Y. Wei(NAOC) on behalf of the SVOM/GWAC team:  

  

We began to observe X-ray transient EP240420a (Zhang et all., GCN 36194) 

detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission,

with GWAC-F50A telescope at Xinglong station, China, at 13:58:11 (UT), 20. April. 2024,    

about 1.9 hours after the burst.   




The weather was not good.  




After stacking 100*100s seconds, the candidate reported (An et al., GCN 23602)or

any other new sources were not detected within the errorbox of EP-FXT (Han et al., GCN 23603) 

in our stacked image  down to a limit magnitude of 19.5 mag 

in R band comparing to several nearby USNO B1.0 stars.  




We acknowledge the excellent support from observation assistant Yangtong ZhengandWenlongDong.