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   PR # 21056
    We propose to observe PKS1209-52.  Its age is estimated to be 2-30000
    yr, similar to the Cygnus Loop and Vela X. It contains a point source
    inside that seems to show a blackbody radiation.  The explosion was  
    strong enough to leave a point souce that would not affect the evolu 
    tion of the expanding shell.  Therefore, the X-ray observation will  
    give us an ISM evolution for the bigger explosion than those left no 
    point source inside like Cygnus Loop.It will give us the ISM density,
    the initial energy and the age. Combining the age, the blackbody temp
    erature will show the thermal history of the point source (probably a
    newtron star).                                                       
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