Upper limit for the number of gamma-ray bursts in 2 - 25 keV energy range from satellite data of the Astron.

An estimate of the upper limit for the number of soft (2 - 25 keV) gamma-ray bursts is made using data obtained with the SKR-2M X-ray telescope onboard the Astron satellite, which was in operation on a high apogee orbit (200000 km) from 1983 to 1990. From 155 observation runs with a duration of 3 - 4 h each the authors deduced the upper limit (in events per year for the full celestial sphere and 50 - 300 keV energy range) N < (2.5 - 9)×10⁴ at the fluence F ≡ 7.3×10^-9erg/cm². This result is in contradiction with the Einstein Observatory data and agrees well with the ROSAT satellite observations.