The monitor of all-sky X-ray image ( MAXI ) Gas Slit Camera ( GSC ) on the International Space Station ( ISS ) detected a gamma-ray burst ( GRB ) on 2009 , September 26 , GRB 090926B .
This GRB had extremely hard spectra in the X-ray energy range .
Joint spectral fitting with the Gamma-ray Burst Monitor on the Fermi Gamma-ray Space Telescope shows that this burst has peculiarly narrow spectral energy distribution and is represented by Comptonized blackbody model .
This spectrum can be interpreted as photospheric emission from the low baryon-load GRB fireball .
Calculating the parameter of fireball , we found the size of the base of the flow r _ { 0 } = ( 4.3 \pm 0.9 ) \times 10 ^ { 9 } Y ^ { \prime -3 / 2 } cm and Lorentz factor of the plasma \Gamma = ( 110 \pm 10 ) Y ^ { \prime 1 / 4 } , where Y ^ { \prime } is a ratio between the total fireball energy and the energy in the blackbody component of the gamma-ray emission .
This r _ { 0 } is factor of a few larger , and the Lorentz factor of 110 is smaller by also factor of a few than other bursts that have blackbody components in the spectra .