DETECTION OF CO-57 GAMMA-RAYS FROM SN-1987A AND PROSPECT OF X-RAY OBSERVATIONS OF THE PULSAR WITH ASUKA

Implications of the detection of gamma-rays from the Co-57 decay in SN 1987A are discussed. The Co-57/Co-56 ratio is compared with the compo sition distribution in the explosion model to infer the neutron star m ass and the explosion mechanism. As an energy source of the light curv e, radioactive decays of Co-57 and Ti-44 could still be possible if th e Ti-44/Ni-56 ratio is larger than 1.8 times the solar Ca-44/Fe-56 rat io. This interpretation with enhanced Ti-44 is less favored by the cur rent nucleosynthesis models but can be tested with the future INTEGRAL experiments. A pulsar with luminosity of approximately 0.2 - 1 X 10(3 7) ergs s-1 at 1 keV - 10 MeV would also be a plausible energy source. This interpretation leads to a prediction that ASUKA (ASCA) may be ab le to observe X-rays from the pulsar at 6 - 10 keV approximately 2 yea rs after the launch.