GCN Circular 36614

Yan-Qiu Zhang, Shao-Lin Xiong report on behalf of the GECAM team:

GECAM-B was triggered in-flight by a long burst, GRB 240604A, at 2024-06-04T22:28:29.050 UTC (T0), which was also detected by INTEGRAL/SPI-ACS (trigger #10730).

According to the realtime alert data of GECAM-B, the GECAM-B light curve shows a long pulse with a duration of ~50 sec (15-1020 keV). The time-averaged spectrum from T0-1 to T0+16 s could be adequately fit by a power law with high energy exponential cutoff function with a fluence of about 7.04E-6 erg/cm^2 in 20-1000 keV.

The GECAM light curve could be found here:
https://twikinew.ihep.ac.cn/pubgecam/Sandbox/GRB/gecam-b_lc_grd_all_combine_171239309.png

The GECAM-B in-flight location (J2000) is: 
Ra: 286.8 deg   
Dec: 79.5 deg
Err: 3.7 deg (1-sigma, statistical only)

The GECAM preliminary location could be found here: 
https://twikinew.ihep.ac.cn/pubgecam/Sandbox/GRB/gecam-b_skymap_flt_171239309.png

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).