TITLE:   GCN CIRCULAR
NUMBER:  29848
SUBJECT: GRB 210420B: AST3-3 YaoAn Optical Observation
DATE:    21/04/21 00:08:17 GMT
FROM:    Tianrui Sun at Purple Mountain Obs,CAS  <trsun@pmo.ac.cn>

Tianrui Sun(Purple Mountain Observatory), Lei Hu, Maokai Hu, Xuefeng Wu, Lei Liu, Kelai Meng, Xiaoyan Li(Nanjing Institute of Astronomical Observation Technology), Zhengyang Li, Xiangyan Yuan, Lifan Wang(TAMU), Xiaofeng Wang (Tsinghua University), report on behalf the AST3 Team:


Following the detection of GRB210420B by Swift (Moss et al. GCN 29844), we use Antarctic Survey Telescope 3-3 at YaoAn Astronomy Observation(China, Yunnan) to follow up. We observed 80 images in the g-band and exposure time in 60 seconds. The observation started at 2021-04-20T20:07:30.596 and ends at 2021-04-20T21:42:43.897. Within the candidate position (A. Oksanen et al. GCN 29846), we detected the source with 16.9 mag at 2021-04-20T20:07:30.596 and 17.5 mag at 2021-04-20T21:42:43.897.