TITLE: GCN CIRCULAR NUMBER: 39340 SUBJECT: GRB 250215A/EP250215a: 1.6m Mephisto optical observation report DATE: 25/02/15 18:49:42 GMT FROM: Brajesh Kumar at SWIFAR, YNU brajesh@ynu.edu.cn
Xiangkun Liu, Yu Pan, Edoardo P. Lagioia, Yaosong Yu, Guowang Du, Brajesh Kumar, Yuan Fang, Jinghua Zhang, Xinlei Chen, Xingzhu Zou, Yuanpei Yang (all SWIFAR, YNU), Xuhui Han, Pinpin Zhang, Liping Xin, Chao Wu, Jianyan Wei (all NAOC), Xiaowei Liu (SWIFAR, YNU) report on behalf of the Mephisto Team:
The field of GRB 250215A/EP250215a detected by Fermi Gamma-ray Burst Monitor (GBM) and EP-WXT (Fermi GBM Team, GCN 39327; Wang et al., GCN 39329) was observed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. Simultaneous uvgr band photometric observations were conducted starting from 16:33:12 2025-02-15 UT (~14 hr after the trigger) and 3 frames with 300s exposure times were taken. There is non-detection of the optical candidate (Liu et al., GCN 39330; Xie et al., GCN 39333; Malesani et al., GCN 39339) in the stacked images of uvgr bands. The preliminary photometry and 3 sigma upper limits are listed below.
Start_Time(UT) | Band | Exp(s)| LimMag (AB) --------------------|--------|-------|------------ 2025-02-15T16:33:12 | u | 300*3 | >20.65 2025-02-15T16:50:23 | v | 300*3 | >20.91 2025-02-15T16:33:12 | g | 300*3 | >21.21 2025-02-15T16:50:23 | r | 300*3 | >21.45
------------------------------------------------------------------------------------------------- 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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