GCN Circular 41631
Subject
EP250901a: Mephisto optical upper limits
Event
Date
2025-09-01T18:00:45Z (19 days ago)
Edited On
2025-09-02T16:18:09Z (18 days ago)
From
liuxk@ynu.edu.cn
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov>
Via
Web form
Xiangkun Liu, Chenxu Liu, Guowang Du, Xufeng Zhu, Yuan Fang, Xingzhu Zou, Shuai Xie, Xiaowei Liu (all SWIFAR, YNU), and Chao Wu (NAOC) report on behalf of the Mephisto Team:
The field of EP250901a, detected by EP-WXT (ID: 00109201113, triggered at 2025-09-01T12:05:03 UTC) and subsequently followed up by EP-FXT (GCN 41627), 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 13:30:37 2025-09-01 UT (~1.5 hr after the trigger) and 6 frames with 45s exposure times were taken. No new optical counterpart was detected (consistent with the upper limits reported by Global MASTER-Net, GCN 41629) 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)
--------------------|------|--------|------------
2025-09-01T13:30:37 | u | 45*6 | >21.68
2025-09-01T13:30:37 | v | 45*6 | >21.77
2025-09-01T13:37:13 | g | 45*6 | >22.17
2025-09-01T13:37:13 | r | 45*6 | >22.31
-------------------------------------------------------------------------------------------------
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.
-------------------------------------------------------------------------------------------------