TITLE: GCN CIRCULAR NUMBER: 43658 SUBJECT: GRB 260208A: GECAM-B observation of a bright burst DATE: 26/02/09 05:50:39 GMT FROM: Xinghao Luo at IHEP <2952704891@qq.com> Xing-Hao Luo, Zheng-Hang Yu, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by GRB 260208A, at 2026-02-08T05:07:30.550 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43635) and Fermi/LAT (Fermi LAT team, GCN #43645). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 38 +2/-1 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260208A.png GECAM-B localized this burst to the following position (J2000): Ra: 128.62 deg Dec: 6.25 deg Err: 0.34 deg (1-sigma, statistical only) The time-averaged spectrum from T0-11.5 s to T0+147.5 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.29 +0.10/-0.08 and the cutoff energy, parameterized as Epeak, is 651 +175/-134 keV. The event fluence (10-1000 keV) in this time interval is (1.62 +0..050/-0.066)E-04 erg/cm^2. Thus GRB 260208A is consistent with Type I GRBs in the 'Amati' relation diagram, as shown at: https://www.bursthub.cn//admin/static/grb250208A_amati.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (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/43658. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...