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We present a systematic X-ray study of eight AGNs with intermediate massblack holes (M_BH 8-95x10^4 Msun) based on 12 XMM-Newton observations. Thesample includes the two prototype AGNs in this class - NGC4395 and POX52 andsix other AGNs discovered with the SDSS. These AGNs show some of the strongestX-ray variability with the normalized excess variances being the largest andthe power density break time scales being the shortest observed amongradio-quiet AGNs. The excess variance -- luminosity correlation appears todepend on both the BH mass and the Eddington luminosity ratio. The break timescale -- black hole mass relations for AGN with IMBHs are consistent with thatobserved for massive AGNs. We find that the FWHM of the Hbeta or Halpha line isuncorrelated with the BH mass, but shows strong anticorrelation with theEddington luminosity ratio. Four AGNs show clear evidence for soft X-ray excessemission (kT_in~150-200eV). X-ray spectra of three other AGNs are consistentwith the presence of the soft excess emission. NGC4395 with lowest L/L_Eddlacks the soft excess emission. Evidently small black mass is not the primarydriver of strong soft X-ray excess emission from AGNs. The X-ray spectralproperties and optical-to-X-ray spectral energy distributions of these AGNs aresimilar to those of Seyfert 1 galaxies. The observed X-ray/UV properties ofAGNs with IMBHs are consistent with these AGNs being low mass extension of moremassive AGNs; those with high Eddington luminosity ratio looking more likenarrow-line Seyfert 1s while those with low $L/L_{Edd}$ looking more likebroad-line Seyfert 1s.

X-ray emission from active galactic nuclei with intermediate mass black holes