TITLE: GCN CIRCULAR NUMBER: 38217 SUBJECT: GRB 241113A: 1.6m Mephisto and 50cm array optical upper limits DATE: 24/11/14 15:11:38 GMT FROM: Brajesh Kumar at SWIFAR, YNU brajesh@ynu.edu.cn
Guowang Du, Brajesh Kumar, Weikang Lin, Yaosong Yu, Yehao Cheng, Yu Pan, Xinlei Chen, Xingzhu Zou, Jinghua Zhang, Yuanpei Yang, Yuan Fang, Xiangkun Liu, Xiaowei Liu (SWIFAR, YNU) report on behalf of the Mephisto Team:
The field of GRB 241113A detected by Swift (Siegel et al., GCN 38194) was observed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) and 50cm array facilities of Yunnan University located at Lijiang Observatory. The observations were initiated after ~4.3 hr with 50cm array and Mephisto telescopes starting from 12:03:04 and 12:08:46 UT on 2024-11-13. Multiple frames (uvgriz and gr bands with Mephisto and 50 cm array) with different exposure time were obtained. The images were suffered with high background due to proximity of the moon. The optical afterglow (Siegel et al., GCN 38194; Francile et al., GCN 38195; Ferrer et al., GCN 38197; Izzo et al., GCN 38201; Ferro et al., GCN 38206; Breeveld et al., GCN 38207; Zheng et al., GCN 38216) was not detected in the stacked images and the 3-sigma upper limits are below.
50CM array Start_Time(UT) Band Exp(s) Lim-mag(AB) 2024-11-13T12:03:05 g 120*2 >19.39 2024-11-13T12:03:04 r 120*2 >19.40
Mephisto Start_Time(UT) Band Exp(s) Lim-mag(AB) 2024-11-13T12:08:46 u 180*4 >20.97 2024-11-13T12:26:51 v 180*2|300*2 >21.34 2024-11-13T12:08:46 g 50*12 >21.41 2024-11-13T12:26:51 r 50*6|300*2 >21.82 2024-11-13T12:08:46 i 79*8 >20.79 2024-11-13T12:26:51 z 79*4|294*2 >20.22
-------------------------------------------------------------------------- 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.
The 50cm array consists of two 50cm telescopes for wide-field surveys and also serves as the supporting facility for monitoring the Mephisto detected targets. --------------------------------------------------------------------------
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