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We present X-ray and multiwavelength studies of a sample of eighthigh-luminosity active galactic nuclei (AGNs) with disc-like H\betaemission-line profiles selected from the Sloan Digital Sky Survey Data Release7. These sources have higher redshift (z~0.6) than the majority of the knowndisc-like emitters, and they occupy a largely unexplored space in theluminosity-redshift plane. Seven sources have typical AGN X-ray spectra withpower-law photon indices of \Gamma~1.4-2.0; two of them show some X-rayabsorption (column density N_H~10^{21}-10^{22} cm^{-2}$ for neutral gas). Theother source, J0850+4451, has only three hard X-ray photons detected and isprobably heavily obscured (N_H>3x10^{23} cm^{-2}). This object is alsoidentified as a low-ionization broad absorption line (BAL) quasar based on MgII \lambda2799 absorption; it is the first disc-like emitter reported that isalso a BAL quasar. The IR-to-UV spectral energy distributions (SEDs) of theseeight sources are similar to the mean SEDs of typical quasars with a UV "bump",suggestive of standard accretion discs radiating with high efficiency, whichdiffers from low-luminosity disc-like emitters. Studies of the X-ray-to-opticalpower-law slope parameters (\alpha_{OX}) indicate that there is no significantexcess X-ray emission in these high-luminosity disc-like emitters. Energybudget analysis suggests that for disc-like emitters in general, the inner discmust illuminate and ionize the outer disc efficiently (~15% of the nuclearionizing radiation is required on average) via direct illumination and/orscattering. Warped accretion discs are probably needed for direct illuminationto work in high-luminosity objects, as their geometrically thin inner discsdecrease the amount of direct illumination possible for a flat disc.

X-ray and Multiwavelength Insights into the Inner Structure of High-Luminosity Disc-Like Emitters