GCN Circular 39894
Subject
GRB 250327B: 1.6m Mephisto optical observations
Event
Date
2025-03-28T01:40:32Z (3 months ago)
Edited On
2025-03-28T14:14:08Z (3 months ago)
From
Brajesh Kumar at SWIFAR, YNU <brajesh@ynu.edu.cn>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Brajesh Kumar at SWIFAR, YNU <brajesh@ynu.edu.cn>
Via
Web form
Jianhui Lian, Brajesh Kumar, Xufeng Zhu, Fanchuan Kong, Yaosong Yu, Yuan Fang, Guowang Du, Xinlei Chen, Yu Pan, Xingzhu Zou, Helong Guo, Jinghua Zhang, Tao Wang, Chenxi Shang, Dan Zhu (all SWIFAR, YNU), Xinzhong Er (TAC, TJNU), Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team:
The field of SVOM GRB 250327B (Bouchet et al., GCN 39888) was observed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. Simultaneous uvgriz band observations were conducted starting from 2025-03-27 T21:14:19 UT (172 seconds after the SVOM/ECLAIRs trigger) to 2025-03-27 T21:21:16 UT. 1 exposure of 180s, 3 exposures of 50s and 2 exposures of 80s in the MEPHISTO uv, gr and iz bands, respectively, were obtained.
The optical afterglow candidate (Moskvitin et al., GCN 39889; Xin et al., GCN 39890; O’Neill et al., GCN 39891; Malesani et al., GCN 39893) is clearly detected in our each frame of v, g, r, i, z band with v-r, g-i color of 3.99 and 1.80 mag, respectively (Galactic extinction correction is not applied). The preliminary magnitudes of the first detections are below:
Start_Time(UT) |Band | Exp(s) | Mag(AB)
--------------------|-----|--------|-----------------
2025-03-27T21:14:19 | u | 180 | >21.22
2025-03-27T21:18:21 | v | 180 | 18.66 +/- 0.075
2025-03-27T21:14:19 | g | 50 | 16.53 +/- 0.013
2025-03-27T21:18:21 | r | 50 | 14.67 +/- 0.003
2025-03-27T21:14:19 | i | 80 | 14.73 +/- 0.004
2025-03-27T21:18:21 | z | 50 | 13.83 +/- 0.004
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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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