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X-ray and multi-wavelength observations of the most luminous known local (z < 0.3) AGN, the recently discovered radio-quiet quasar PDS 456, are presented. The spectral energy distribution shows that PDS 456 has a bolometric luminosity of 10[sup 47] erg/s, peaking in the UV. The X-ray spectrum obtained by ASCA and RXTE shows considerable complexity. The most striking feature observed is a deep, highly-ionised, iron K edge (8.7 keV, rest-frame), originating via reprocessing from highly ionised material, possibly the inner accretion disk. PDS 456 was found to be remarkably variable for its luminosity; in one flare the X-ray flux doubled in just ∼ 15 ksec. If confirmed this would be an unprecedented event in a high-luminosity source, with a light-crossing time corresponding to ∼ 2R[sub S]. The implications are that either flaring occurs within the very central regions, or else that PDS 456 is a 'super-Eddington' or relativistically beamed system. [ABSTRACT FROM AUTHOR]

We present a systematic analysis of the X-ray spectral properties of a sample of 22 'narrow-line' Seyfert I galaxies for which data are available from the ASCA public archive. We also consider the spectrum of the bright NLS1 Ark 564 in detail using simultaneous ASCA and RXTE data. [ABSTRACT FROM AUTHOR]