EP241201a: 1.6m Mephisto Optical Upper Limits

The field of EP241201a (Chen et al., GCN 38415) was observed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory starting from 11:21:59 UT 2024-12-04 (~2.5 days after the trigger). Several frames with exposures of 300s and 294s in the uvgr and iz bands were taken. In the stacked images, no credible candidate was detected within the EP-WXT error circle (Chen et al., GCN 38415) and at the location of possible source (Lee et al., GCN 38418). This is consistent with the reports by Liu et al. (GCN 38425), and Perez-Garcia et al. (GCN 38427). The 3-sigma upper limits are listed below. Start_Time(UT) Band Exp(s) Lim-mag(AB) 2024-12-04T11:22:00 u 300*3 >21.93 2024-12-04T11:38:30 v 300*3 >22.34 2024-12-04T11:21:59 g 300*3 >22.29 2024-12-04T11:38:30 r 300*3 >22.59 2024-12-04T11:22:00 i 294*3 >21.23 2024-12-04T11:38:31 z 294*2 >20.18 -------------------------------------------------------------------------- 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. --------------------------------------------------------------------------