TITLE: GCN CIRCULAR NUMBER: 6252 SUBJECT: GRB 070406: The exprosure time of Xinglong TNT optical Upper Limit DATE: 07/04/07 08:36:52 GMT FROM: L.P. Xin at NAOC W.K. Zheng, M.Zhai, Y.L. Qiu, J.Y. Wei, J.Y. Hu, J.S. Deng, Y. Urata, J.Z. Li and L.P. Xin on behalf of EAFON report: I want to make a apologize that I have forgotten to provide you the exposure time of the combined image in CGN 6250, that was 1090s . This message may be cited