TITLE: GCN CIRCULAR NUMBER: 39656 SUBJECT: EP250308a: 1.6m Mephisto optical upper limits DATE: 25/03/10 17:46:43 GMT FROM: Brajesh Kumar at SWIFAR, YNU brajesh@ynu.edu.cn
Shiyan Zhong, Jinghua Zhang, Guowang Du, Xin Chang, Bin Yan, Xingzhu Zou, Brajesh Kumar, Yuan Fang, Helong Guo, Edoardo P. Lagioia, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team:
The field of EP250308a (Yin et al., GCN 39625) was observed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. Two exposures of 180s in the MEPHISTO u band, and six exposures of 50s in the MEPHISTO g band were simultaneously (ug) obtained starting from 2025-03-09T20:07:03 (~27h after the trigger). In our stacked u and g band images, we did not detect any source at the position reported by Yin et. al., GCN 39625. The preliminary 3-sigma upper limits are below, which is consistent with previously reported GCN (Zhu et al., GCN 39624; Busmann et al., GCN 39626; Lipunov et al. GNC 39628).
Start_Time(UT) | Band | Exp(s) | LimMag(AB) --------------------|------|--------|------------ 2025-03-09T20:07:03 | u | 180*2 | >22.20 2025-03-09T20:07:03 | g | 50*6 | >22.38 ------------------------------------------------------------------------------------------------- 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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