TITLE: GCN CIRCULAR NUMBER: 30787 SUBJECT: GECAM observation of a burst from SGR J1555.2-5402 DATE: 21/09/09 14:49:12 GMT FROM: Zhao Yi at POLAR <yizhao@ihep.ac.cn> Yi Zhao, S. Xiao, S. L. Xiong, L. Lin, C. Cai, 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 on-ground by a bright short burst from SGR J1555.2-5402 at 2021-09-07T19:15:21.100 UTC (T0), which was also detected by Fermi/GBM. According to the GECAM-B light curves in about 15-60 keV, this burst mainly consists of a single pulse with T90 of 18 ms measured from T0-0.014 s. The GECAM light curve could be found here: http://twiki.ihep.ac.cn/pub/GECAM/GRBList/SGR20210907T191521.100-Lc.png Since this burst has very few counts registered on GECAM-B detectors, the location given by GECAM-B alone is quite coarse but broadly consistent with SGR J1555.2-5402. According to our multiple-mission joint location pipeline (S. Xiao et al., accepted by ApJ) using GECAM-B and Fermi/GBM data, this burst is localized to an annulus which is very consistent with SGR J1555.2-5402. The GECAM-GBM joint location could be found here: http://twiki.ihep.ac.cn/pub/GECAM/GRBList/SGR20210907T191521.100-JointLoc.pn... Considering these results stated above and some activities reported recently, we conclude that this burst is from SGR J1555.2-5402. 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).