TITLE: GCN CIRCULAR NUMBER: 30985 SUBJECT: GECAM detection of a short burst probably from SGR J1555.2-5402 DATE: 21/10/25 03:44:59 GMT FROM: Ce Cai at IHEP <caice@ihep.ac.cn> C. Cai, S. Xiao, Yi Zhao, S. L. Xiong, J. J. He, Y. Huang, Z. W. Guo, C. Y. Li, X. B. Li, J. C. Liu, X. Y. Song, C. W. Wang, P. Wang, S. L. Xie, W. C. Xue, Q. B. Yi, Y. Q. Zhang, G. Y. Zhao, X. Y. Zhao, C. Zheng, Y. Q. Du, D. Y. Guo, J. Liang, F. J. Lu, Q. Luo, X. Ma, W. X. Peng, R. Qiao, L. M. Song, J. Wang, H. Wu, P. Zhang, S. N. Zhang, X. L. Zhang, Z. Zhang, S. J. Zheng (IHEP), report on behalf of GECAM team: During the commissioning phase, GECAM-B was triggered in-flight by a bright short burst (trig# 88823384) at 2021-10-25T01:09:44.250 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 BDS alert data, this burst mainly consists of a single pulse with a duration of about 50 ms. Using the light curves and spectrum in the BDS alert data, GECAM-B localized this burst to the following position (J2000): Ra: 244.40 deg Dec: -64.997 deg Err: 17.63 deg (1-sigma, statistical only) The current systematic error of location is estimated to be several degrees. This location is consistent with SGR J1555.2-5402 within the error. The GECAM light curve could be found here: http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_grd_all_combine_88823384... As the detailed science data are downloaded, all analyses would be improved. 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).