GCN Circular 35325

Yue Wang, Shao-Lin Xiong report on behalf of the GECAM team:

GECAM-C was triggered in-flight by a likely short burst, GRB 231212A, at 2023-12-12T00:56:48.850 UTC (T0), which was also triggered by Fermi/GBM (TrigNum724035412) . 

According to the realtime alert data, the GECAM-C light curve shows a short pulse with a duration of ~4 sec (15-1050 keV). 

The time-averaged spectrum of GECAM-C realtime data from about T0-2 s to T0+2 s could be
adequately fit by a cut-off power-law with a flux about 8.01E-7 erg/cm^2/s in 20-1000 keV.

Using the automatic on-ground localization pipeline with the realtime alert data, 
GECAM-C localized this burst to the following position (J2000): 
Ra:  151.1 deg 
Dec: -74.1 deg
Err: 7.1 deg (1-sigma, statistical only)

The GECAM light curve and localization could be found here: 
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/231212A_lc.jpg
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/231212A_loc.png

We note that these results are based on realtime alert data and thus very preliminary. 

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM) mission originally consists of two microsatellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS).