Hard X-ray radiation from supernova 1987A. The results of the "Roentgen" Observatory observations onboard the "Kvant" module in 1987-1989.

Observations performed with the Hexe instrument onboard the Kvant module indicate that, by May-June 1989, the hard X-ray flux from SN1987 had declined by more than a factor of 8 compared with the maximum of the X-ray light curve. The upper limits to the Co-57/Co-56 abundance ratio at the level of three standard deviations was obtained. The value of this ratio exceeds that of the Fe-57/Fe-56 ratio on earth by a factor of 1.5.