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   61068
   SN 1993J is one of five recent supernova explosions (SNe) detected in
   X-rays. It is observationally unprecedented, in that it is the only SNe
   detected in the radio and in X-rays within a week of the explosion, and
   whose X-ray light curve and spectral evolution have been carefully
   measured for over one year. Recently, the X-ray light curves shows
   increase and decrease whose origin is still not known. This time
   variability implies many important features, such as the expansion of
   the shock wave, and as circumstellar density profile. Thus, continuous
   monitoring is urged. Furthermore, we also expect to detect emission
   from a pulsar, if it is as bright as Crab pulsar.
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