TITLE: GCN CIRCULAR NUMBER: 41094 SUBJECT: GRB 250713A: Mephisto optical upper limits DATE: 25/07/15 05:31:26 GMT FROM: Brajesh Kumar at SWIFAR, YNU brajesh@ynu.edu.cn
Helong Guo, Yuan Fang, Yuze Zhao, Runnan Jiang, Guowang Du, Xingzhu Zou, Xinlei Chen, Yu Pan, Xufeng Zhu, Tao Wang, Jinghua Zhang, Brajesh Kumar, Edorardo Lagioia, Dezi Liu, Chenxu Liu, Shiyan Zhong, Weikang Lin, Jianhui Lian, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team:
Simultaneous multi-band photometric observations of the SVOM GRB 250713A (Maggi et al., GCN 41078) were performed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. The observations started from 17:11:19 2025-07-13 UT (~5 minutes after the trigger), and several frames were obtained in uvgr bands. In our stacked images, no new optical source was detected within the SVOM/MXT error region and in particular at the EP/FXT Source 2 position (Liang et al., GCN 41085). The 3-sigma upper limits are below:
Start_Time(UT) Band Exp (sec) LimMag(AB) 2025-07-13T17:11:19 u 45*6 >20.53 2025-07-13T17:32:27 v 45*6 >20.65 2025-07-13T17:11:19 g 45*6 >21.17 2025-07-13T17:32:27 r 45*6 >21.32
Our results are consistent with Fu et al. (GCN 41079), Wu et al. (GCN 41089), Braun et al. (GCN 41090), Saccardi et al. (GCN 41091) and Li et al. (GCN 41092).
---------------------------------------------------------------------------- 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. ----------------------------------------------------------------------------
View this GCN Circular online at https://gcn.nasa.gov/circulars/41094. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...