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

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 II GRBs in the 'Amati' relation diagram, as shown at: 
https://www.bursthub.cn//admin/static/gecambgrb260208A_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).