TITLE: GCN CIRCULAR NUMBER: 30874 SUBJECT: GRB 210923B: GECAM detection DATE: 21/09/24 06:05:39 GMT FROM: Xiaolu Zhang at IHEP <xlzhang@ihep.ac.cn> GRB 210923B: GECAM detection X. L. Zhang, S. L. Xiong, X. Y. Zhao, Y. Huang, X. Y. Song, C. Cai, S. Xiao, S. L. Xie, Y. Q. Zhang, Y. Zhao, Z. W. Guo, 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, J. C. Liu, L. M. Song, F. J. Lu, S. N. Zhang (IHEP), report on behalf of GECAM team: During the commissioning phase, GECAM-B was triggered ground by a short bright burst, GRB 210923B, at 2021-09-23 02:11:29.000 UTC (denoted as T0), which was also detected by Konus-Wind. According to the GECAM-B light curves in about 15-3500 keV, this burst mainly consists of a broad pulse with a duration of about 0.679 s. The GECAM light curve could be found here: http://twiki.ihep.ac.cn/pub/GECAM/GRBList/utn210923_021129_GECAMb_lc.png GECAM-B localized this burst to the following position (J2000): Ra: 287.25 deg Dec: -12.03 deg Err: 6.29 deg (1-sigma, statistical only) The current systematic error of location is estimated to be several degrees which could be minimized by the ongoing calibration. 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).