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   63034
   Short term variation of the absorbing column density in the highly
   redshifted quasar S5 0836+710 (z = 2.172) was previously observed. An
   increase by a factor 4 within 0.8 years (quasar frame) was reported and
   sets stringent constraints on the location of the absorber. This is the
   first finding of relatively high AND variable absorption in a quasar at
   high redshift and strengthens the hypotheses of a population of
   absorbed AGN at high redshift which is postulated to explain the X-ray
   background. To confirm the presence of high and variable absorption and
   to investigate the time scale of the variation four observations of the
   quasar S5 0836+710 with ASCA for a total of 80 ksec are proposed.
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