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   PR # 41074
   We propose to observe HB-3 supernova remnant. HB-3 has quite complex
   structures: X-ray ring at the center, radio shell around the X-ray
   ring , and HI shell around the radio shell. HB-3 is the only target
   which have already known to the explosion/expansion in a hot bubble.
   A hot bubble would occupy a half of our galaxy and most of SN
   explosions must occur in bubble. However, such explosions are hard to
   be observed and have not been well studied yet. So, HB-3 is a good
   sample to study the evolution of SNRs in a hot bubble, because it is
   already known to be in such conditions.
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