GCN Circular 30787

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.png

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).