The hard X-ray spectrum of SN 1987A.

The discovery of hard X-rays in the energy range from 20 to 350 keV by the Hexe and Pulsar X-1 instruments on the Mir-Kvant Rontgen observatory is reported. The hard X-rays were first observed on August 10, 1987, and thereafter SN 1987A became the main target of the observatory. The measured spectrum is extremely hard. At high energies the photon spectrum has a power law index of about 1.4. At lower energies the spectrum becomes flatter and there is indication of a cut-off below 25 keV. The luminosity in the above energy band is about 2 x 10 to the 38th erg/s. The flux shows little variation between August 10 and begining of October.