GCN Circular 36602

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

GECAM-B was triggered in-flight by a weak short burst, GRB 240603A, at 2024-06-03T02:27:33.950 UTC (T0), which was also detected by INTEGRAL/SPI-ACS (trigger #10729).

The GECAM-B in-flight location (J2000) is: 
Ra: 3.5 deg   
Dec: -18.5 deg
Err: 5.9 deg (1-sigma, statistical only)

According to the realtime alert data of GECAM-B, this burst mainly consists of a spike and a tail with a total duration of about 1 s. The time-averaged spectrum from T0-0.5 s to T0 could be adequately fit by a power law with high energy exponential cutoff function with a fluence of about 1.21E-6 erg/cm^2 in 20-1000 keV.

We note that these results are very preliminary. Refined analysis will be reported later.

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).