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   51101
   Because of its proximity, SN1987A is providing us with a unique
   opprtunity to study an SNR in its very early phase of evolution. ROSAT
   detected soft X-rays from the SN in 1991, whose origin is probably the
   shock formed by the colliding ejecta and the wind remnant of the
   progenitor. In 1995, ASCA also detected the X-ray emission with flux of
   about 1E-13 erg/cm2/sec. Given the distribution of the circumstellar
   matter aroung the SN, increase of the X-ray luminosity is expected as
   the ejecta expands. Time evolution of the luminosity and spectrum will
   give valuable information on the circumstellar matter and the mass loss
   history of the progenitor.
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