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   71192
   We propose total 160 ks observation of a dark lensing cluster of galaxy
   RXJ105346.6+573517, which has been detected in the ROSAT ultra-deep HRI
   survey of the Lockman Hole. This object has an unusual double-humped
   extended X-ray profile and the brightest galaxy (z=2.570) close to the
   center of the eastern emission peak shows a gravitationally lensed arc,
   confirming this object as a cluster, but no significant redshift
   association of galaxies are found. We aim to have an X-ray spectrum of
   this object with ASCA and determine its temperature and possibly
   redshift. We also emphasize that this additional observing time of the
   Lockman Hole enables us to gain a lot more information on all other
   sources in the field, in particular time variability.
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