TITLE: GCN CIRCULAR NUMBER: 38252 SUBJECT: GRB 241113B: Mephisto upper limits DATE: 24/11/16 14:23:37 GMT FROM: Brajesh Kumar at SWIFAR, YNU Guowang Du, Brajesh Kumar, Weikang Lin, Yaosong Yu, Yehao Cheng, Yu Pan, Xinlei Chen, Xingzhu Zou, Jinghua Zhang, Yuanpei Yang, Yuan Fang (all SWIFAR, YNU), Xuhui Han, Pinpin Zhang, Liping Xin, Chao Wu (all NAOC), Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team: The field of GRB 241113B (SVOM/ECLAIRs, Dagoneau et al., GCN 38196; SVOM/GRM, Liu et al., GCN 38212; EP/WXT, Liu et al., GCN 38214) was observed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory starting from 16:17:01 UT 2024-11-13 (~4.9 hr after the trigger). Six simultaneous frames in vrz bands were taken with 300s each exposure. The optical afterglow candidate reported by Zheng et al. (GCN 38232) is not visible in our stacked images. The 3-sigma upper limits are below. Start_Time(UT) Band Exp(s) Lim-mag(AB) 2024-11-13T16:17:01 v 300*6 >22.18 2024-11-13T16:17:01 r 300*6 >22.79 2024-11-13T16:17:01 z 300*6 >21.07 -------------------------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The on-site telescope assemblage and commissioning were carried out in September 2022. The first light in all three channels was achieved on 2023 December 21. --------------------------------------------------------------------------