TITLE: GCN CIRCULAR NUMBER: 38854 SUBJECT: GRB 250103A: 1.6m Mephisto optical observations DATE: 25/01/08 16:27:20 GMT FROM: Brajesh Kumar at SWIFAR, YNU brajesh@ynu.edu.cn
Guowang Du, Jinghua Zhang, Yangwei Zhang, Brajesh Kumar, Xufeng Zhu, Fanchuan Kong, Chenxi Shang, Yuan Fang, Xinlei Chen, Xingzhu Zou, Yu Pan, Yuanpei Yang (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 250103A (sb25010301) detected by SVOM/ECLAIRs (Wang et al. GCN 38786) was observed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. Simultaneous uvgriz band photometric observations were conducted starting from 11:35:51 2025-01-03 UT (~1.65 hr after the SVOM/ECLAIRs trigger) and several frames with different exposure times were taken. There is detection of the optical candidate (Li et al., GCN 38795; Qiu et al., GCN 38802; Xu et al., GCN 38808; Leonini et al., GCN 38811) in our r and i band single frames but not in the stacked images of uvgz bands. The preliminary photometry and 3 sigma upper limits are below:
Start_Time(UT) | Band | Exp(s) | Mag/LimMag (AB) ---------------------------|--------|---------------- 2025-01-03T11:35:52 | u | 180*2 | >21.89 2025-01-03T11:43:02 | v | 180*2 | >22.28 2025-01-03T11:35:52 | g | 50*6 | >22.15 2025-01-03T11:43:03 | r | 50*1 | 20.91(+/-0.35) 2025-01-03T11:35:51 | i | 79*1 | 19.72(+/-0.32) 2025-01-03T11:43:02 | z | 79*4 | >20.46
------------------------------------------------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m 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. -------------------------------------------------------------------------------------------------
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