Long term X-ray variability characteristics of the narrow-line Seyfert 1
  galaxy RE~J1034+396
  We present the results of our study of the long term X-ray variability
characteristics of the Narrow Line Seyfert 1 galaxy RE J1034+396. We use data
obtained from the AstroSat satellite along with the light curves obtained from
XMM-Newton and Swift-XRT. We use the 0.3 - 7.0 keV and 3 - 20 keV data,
respectively, from the SXT and the LAXPC of AstroSat. The X-ray spectra in the
0.3 - 20 keV region are well fit with a model consisting of a power-law and a
soft excess described by a thermal-Compton emission with a large optical depth,
consistent with the earlier reported results. We have examined the X-ray light
curves in the soft and hard X-ray bands of SXT and LAXPC, respectively, and
find that the variability is slightly larger in the hard band. To investigate
the variability characteristics of this source at different time scales, we
have used X-ray light curves obtained from XMM-Newton data (200 s to 100 ks
range) and Swift-XRT data (1 day to 100 day range) and find that there are
evidences to suggest that the variability sharply increases at longer time
scales. We argue that the mass of the black hole in RE J1034+396 is likely to
be $\sim$3 $\times$ 10$^6$ M$_\odot$, based on the similarity of the observed
QPO to the high frequency QPO seen in the Galactic black hole binary, GRS
1915+105.
