TITLE:   GCN CIRCULAR
NUMBER:  35266
SUBJECT: GRB 231205A: GECAM-B detection of a short burst
DATE:    23/12/05 03:48:51 GMT
FROM:    tanwj@ihep.ac.cn

GRB 231205A: GECAM-B detection of a short burst

Wenjun Tan, Shaolin Xiong, report on behalf of the GECAM team:

GECAM-B was triggered in-flight by a short burst, GRB 231205A
at 2023-12-05T02:25:11.450 UTC(T0), which was also observed by 
Fermi/GBM (Fermi/GBM team, GCN 35263).

According to the realtime alert data of GECAM-B, this burst consists 
of one bright short pulse followed by weaker emission with a total 
duration (T90) of about ~0.3 sec (30-1020 keV).

Using the automatic on-ground localization pipeline with the realtime alert data, 
GECAM-B localized this burst to the following position (J2000): 
Ra: 202.8 deg 
Dec: 26.8 deg
Err: 6.1 deg (1-sigma, statistical only)
GECAM location is consistent with that of Fermi/GBM within the error.

The time-averaged spectrum of GECAM-B realtime data from about T0-0.05 s to T0 could be
adequately fit by a cut-off power-law with a fluence about 1.10E-6 erg/cm^2 in 20-1000 keV. 

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).