TITLE: GCN CIRCULAR NUMBER: 30794 SUBJECT: GECAM observation of a burst from SGR J1935+2154 DATE: 21/09/10 02:47:18 GMT FROM: Shuo Xiao at IHEP <xiaoshuo@ihep.ac.cn> S. Xiao, S. L. Xiong, Y. Zhao, X. Y. Zhao, Y. Huang, X. Y. Song, C. Cai, S. L. Xie, Y. Q. Zhang, Z. W. Guo, J. C. Liu, C. Zheng, W. C. Xue, C. Y. Li, C. W. Wang, Q. B. Yi, B. X. Zhang, P. Zhang, W. X. Peng, R. Qiao, D. Y. Guo, X. B. Li, X. Ma, P. Wang, J. Wang, Z. Zhang, S. J. Zheng, W. Chen, J. J. He, G. Y. Zhao, Y. Q. Du, H. Wu, J. Liang, Q. Luo, X. L. Zhang, L. M. Song, F. J. Lu, S. N. Zhang (IHEP), report on behalf of GECAM team: During the commissioning phase, GECAM-B was triggered in-flight by a bright short burst (trig# 84938908) at 2021-09-10T02:08:28.800 UTC (T0), Its alert data was promptly downlinked to the ground through the short message service of BeiDou Navigation Satellite System (BDS). The time latency of the first BeiDou message relative to the trigger time is about 1 minute. According to the GECAM-B light curves in about 15-65 keV, this burst mainly consists of a single pulse with a duration about 100 ms. The location is consistent with SGR J1935+2154 within the error. The GECAM light curve could be found here: http://twiki.ihep.ac.cn/pub/GECAM/GRBList/utn210910_020828_GECAMb.png Please note that all GECAM results here are preliminary. The final analysis will be published in journal papers or GECAM online catalog. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time), which was funded by the Chinese Academy of Sciences (CAS).