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   71140
   Active galactic nuclei show time variability, and using the variability
   time scale, we estimated the size of the emitting region. The size was
   often used to deduce the mass of central black hole in the galaxy.
   Seyfert 1 galaxy show fast time variability with the time scale less
   than 1000 seconds, which corresponds to black hole mass of 2E7 solar
   mass. On the other, there are only a few reports on fast time
   variability less than 1 day for Seyfert 2 galaxy. The time scale of 1
   day corresponds to the black hole mass of 1E9 solar mass. Since we have
   not detected short time variability for most of Seyfert 2 galaxy,
   Seyfert 2 galaxy might have super massive black hole similar to QSO. We
   propose to examine the time variability of Seyfert 2 galaxy.
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