GCN Circular 36334

Yuan-Pei Yang, Xin-Lei Chen, Brajesh Kumar, Xinzhong Er, Jinghua Zhang, Prospero Lagioia Edoardo, Tianrui Sun, Guowang Du, Xiangkun Liu, Yu Wang, Gaofan Feng, Lei Yang, Xingzhu Zou, Yu Pan, Weikang Lin, Yuan Fang, Chenxu Liu, Shiyan Zhong, Xiaowei Liu (SWIFAR, YNU)

We performed simultaneous multi-band photometric observations in response to the gravitational wave candidate LIGO/Virgo/KAGRA S240422ed (GCN 36236
Not found
 
 
) and the suggested X-ray counterpart  (EP240426a, GCN 36313
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). The observation began on 2024-04-26 (12:35:44 UT) using the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University at Lijiang Observatory (IAU code: 044) of Yunnan Astronomical Observatories, Chinese Academy of Sciences. Multiple frames in u, v, g, r, i, and z bands were obtained in moderate sky conditions. In our preliminary analysis on co-added images, the transient (GCN 36331
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, GCN 36333
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) is not detected at the 5 sigma limit. The pre-processing and preliminary photometry of the images were done with automatic data reduction and photometry pipeline developed for the Mephisto. Here, we note that the Mephisto filter system (u, v, g, r, i, and z) mean transmission wavelengths are 345, 385, 530, 630, 837 and 945 nm and the effective band widths are 38, 37, 79, 102, 109 and 71 nm.

Start time (UT) | Filter | Mag (AB)
12:35:44 | u | >19.10
12:35:44 | g | >19.85
12:35:44 | i | >19.58 
12:59:16 | v | >19.97
12:59:16 | r | >20.18
12:59:16 | z | >18.75
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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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