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). View this GCN Circular online at https://gcn.nasa.gov/circulars/35266. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...