GCN Circular 43823
Subject
EP260213a: Mephisto optical upper limits
Event
Date
2026-02-25T04:33:50Z (a day ago)
From
Brajesh Kumar at SWIFAR, YNU <brajesh@ynu.edu.cn>
Via
Web form
Guowang Du, Ziwei Li, Zhenfei Qin, Jialong Zhou, Yu Pan, Xingzhu Zou, Xinlei Chen, Brajesh Kumar, Yuan Fang, Jinghua Zhang, Xufeng Zhu, Tao Wang, Xinzhong Er, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (SWIFAR, YNU) report on behalf of the Mephisto Team:
The 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University, located at the Lijiang Observatory, was triggered at 2026-02-13T20:05:57 (~7.2 min after the EP/WXT trigger) to observe the field of EP260213a (Yang et al., GCN 43729; Li et al., GCN 43730). A set of simultaneous multi-band (ugi and vrz) images was collected. In our stacked frames, no new candidate was detected within the EP/FXT localization (Li et al., GCN 43730) and the upper limits (3 sigma) are listed below. These results are consistent with previously reported non-detection by Cotter et al. (GCN 43728), Wu et al. (GCN 43731), Maksut et al. (GCN 43732), Pankov et al. (GCN 43733), Li et al. (GCN 43734), Aryan et al. (GCN 43735), Fortin et al. (GCN 43737), Lipunov et al. (GCN 43738) and Eyles-Ferris et al. (GCN 43739).
---------------------------------------------------
Start_Time(UT) | Band | Exp(s) | LimMag (AB)
---------------------------------------------------
2026-02-13T20:11:30 | u | 45.0*8 | >22.68
2026-02-13T20:05:57 | v | 45.0*5 | >22.62
2026-02-13T20:11:33 | g | 45.0*8 | >23.51
2026-02-13T20:05:59 | r | 45.0*5 | >23.41
2026-02-13T20:13:07 | i | 45.0*8 | >22.84
2026-02-13T20:05:59 | z | 45.0*5 | >21.85
---------------------------------------------------
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. The facility is operated by the South-Western Institute for Astronomy Research (SWIFAR), Yunnan University. It provides real-time, high-quality colors of stellar objects. The Mephisto mosaic cameras were installed in October 2025. The first light was achieved in all three channels on 10 October 2025 and presently, these are under the commissioning phase. All the data have been reduced by the Mephisto data processing pipeline. Here, we note that the current data processing pipeline is still at a preliminary stage, with flux calibration precision in each band at the level of about 5% or even higher.