GCN Circular 37377

Yan-Qiu Zhang (IHEP), Shao-Lin Xiong (IHEP), Chen-Wei Wang (IHEP) report on behalf of the GECAM team:

GECAM-C was triggered on-ground by a long burst, GRB 240828A, at 2024-08-28T14:55:07.150 UTC (T0), which was also detected by Fermi/GBM (Fermi GBM team, GCN #37317
Not found
 
 
; S. Dalessi et al., GCN #37341
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), AstroSat CZTI (S. Srijan et al., GCN #37328
Not found
 
 
), Fermi-LAT (R. Gupta et al., GCN #37331
Not found
 
 
), Swift-XRT (A.P. Beardmore et al., GCN #37337
Not found
 
 
) and INTEGRAL/SPI-ACS (trigger #10876).

According to the GECAM-C light curves in about 6-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of about 41.41（+1.13,-1.05）s.
The time-averaged spectrum from T0+0.83 to T0+42.24 s could be fit by a power law with high energy exponential cutoff function with a fluence of about 7.77E-05 erg/cm^2 in 10-1000 keV.

The GECAM light curve could be found here:
https://twikinew.ihep.ac.cn/pubgecam/Sandbox/GRB/GECAMC_lC_GRB240828A.png

The GECAM-C on-ground location (J2000) is: 
Ra: 227.7 deg   
Dec: 39.9 deg
Err: 1.8 deg (1-sigma, statistical only)

GECAM location is consistent with the Fermi/LAT position within the error.

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).