GECAM detection of a short GRB 210119A or a new SGR candidate Swift J1851.2-6148

During the commissioning phase, one satellite of GECAM mission, GECAM-B, was triggered by a short GRB 210119A or a new SGR candidate Swift J1851.2-6148 at 2021-01-19T02:54:09.850 (T0). This burst was also observed by Fermi/GBM (GCN #29322), Swift/BAT (GCN #29323) and Insight-HXMT (GCN #29329). According to the GECAM-B light curves in about 8 keV-4 MeV, this burst consists of a single pulse with a duration (T90) of 38.03 +/- 0.62 ms. The 20-ms peak counts rate is about 7000 cps while the total counts is about 360 counts. A prominent spectral variation across the burst duration is evident especially below 25 keV. The spectral hardness measured by GECAM-B suggests that this bust is more likely a short GRB rather than a typical SGR. The GECAM light curve could be found here: http://twiki.ihep.ac.cn/pub/GECAM/GRBList/GECAM-B-tn210119_025409.png Although the in-flight calibration of energy response and localization has not been finalized yet, and this burst is rather short and weak, GECAM-B localized this burst to the following position (J2000): ra: 284.3 deg dec: -60.4 deg err: 6.4 deg which is consistent with the position given by Swift/BAT within the error. Please note that all GECAM results here are preliminary. The final analysis will be published in journal papers or GECAM online catalog. This is the first published burst detected by GECAM mission. 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).