TITLE: GCN CIRCULAR NUMBER: 10092 SUBJECT: GRB 091024: YNAO-GMG observations DATE: 09/10/27 12:12:05 GMT FROM: Jirong Mao at Yunnan Obs J. Mao (YNAO & INAF-OAB), S. Li and J. Bai (YNAO) report on behalf of the GMG group: We observed the optical afterglow of GRB 091024 (Marshall et al., GCN 10062) using one 2.4-m telescope located at Gao-Mei-Gu (GMG, Yunnan Observatory) about 3 hours after the trigger. Some preliminary results are shown below: Start UT Filter mag err ------------------------------------- 11:52:13 R 19.66 0.02 12:54:35 R 20.18 0.03 15:11:33 R 21.03 0.05 All the calibrations were processed by nearby USNO stars in the images and without extinction correction. The detailed analysis is ongoing. This message might be cited.