The GRB221009A gamma-ray burst as revealed by the gamma-ray spectrometer onboard the KPLO (Danuri).

ABSTRACT

The strongest gamma-ray burst (GRB) of the century, GRB20221009A, has been detected by the Korean Pathfinder Lunar Orbiter Gamma-ray Spectrometer (KGRS) instrument onboard the Korean Pathfinder Lunar Orbiter (KPLO). KGRS uses a LaBr3 detector to measure GRB counts with five energy bins in the energy range from 30 keV to 12 MeV. KGRS detected GRB221009A at a distance of 1.508 million kilometers from the Earth. The full duration of the main burst was recorded between 1320 and 1326 on October 9, 2022 with peak counts of over 1000 times background. The dead time of KGRS reached as high as 50%, and the intrinsic gamma-ray spectrum of LaBr3 was significantly altered.