We present a systematic X-ray study of eight active galactic nuclei ( AGNs ) with intermediate mass black holes ( M _ { BH } \sim 8 - 95 \times 10 ^ { 4 } { ~ { } M _ { \odot } } ) based on 12 XMM-Newton observations .
The sample includes the two prototype AGNs in this class – NGC 4395 and POX 52 and six other AGNs discovered with the Sloan Digitized Sky Survey .
These AGNs show some of the strongest X-ray variability with the normalized excess variances being the largest and the power density break time scales being the shortest observed among radio-quiet AGNs .
The excess variance – luminosity correlation appears to depend on both the BH mass and the Eddington luminosity ratio .
The break time scale – black hole mass relations for AGN with IMBHs are consistent with that observed for massive AGNs .
We find that the FWHM of the H \beta /H \alpha line is uncorrelated with the BH mass , but shows strong anticorrelation with the Eddington luminosity ratio .
Four AGNs show clear evidence for soft X-ray excess emission ( kT _ { in } \sim 150 - 200 { ~ { } eV } ) .
X-ray spectra of three other AGNs are consistent with the presence of the soft excess emission .
NGC 4395 with lowest L / L _ { Edd } lacks the soft excess emission .
Evidently small black mass is not the primary driver of strong soft X-ray excess emission from AGNs .
The X-ray spectral properties and optical-to-X-ray spectral energy distributions of these AGNs are similar to those of Seyfert 1 galaxies .
The observed X-ray/UV properties of AGNs with IMBHs are consistent with these AGNs being low mass extension of more massive AGNs ; those with high Eddington luminosity ratio looking more like narrow-line Seyfert 1s while those with low L / L _ { Edd } looking more like broad-line Seyfert 1s .