X-ray and Multiwavelength Insights into the Inner Structure of
  High-Luminosity Disc-Like Emitters
  We present X-ray and multiwavelength studies of a sample of eight
high-luminosity active galactic nuclei (AGNs) with disc-like H\beta
emission-line profiles selected from the Sloan Digital Sky Survey Data Release
7. These sources have higher redshift (z~0.6) than the majority of the known
disc-like emitters, and they occupy a largely unexplored space in the
luminosity-redshift plane. Seven sources have typical AGN X-ray spectra with
power-law photon indices of \Gamma~1.4-2.0; two of them show some X-ray
absorption (column density N_H~10^{21}-10^{22} cm^{-2}$ for neutral gas). The
other source, J0850+4451, has only three hard X-ray photons detected and is
probably heavily obscured (N_H>3x10^{23} cm^{-2}). This object is also
identified as a low-ionization broad absorption line (BAL) quasar based on Mg
II \lambda2799 absorption; it is the first disc-like emitter reported that is
also a BAL quasar. The IR-to-UV spectral energy distributions (SEDs) of these
eight sources are similar to the mean SEDs of typical quasars with a UV "bump",
suggestive of standard accretion discs radiating with high efficiency, which
differs from low-luminosity disc-like emitters. Studies of the X-ray-to-optical
power-law slope parameters (\alpha_{OX}) indicate that there is no significant
excess X-ray emission in these high-luminosity disc-like emitters. Energy
budget analysis suggests that for disc-like emitters in general, the inner disc
must illuminate and ionize the outer disc efficiently (~15% of the nuclear
ionizing radiation is required on average) via direct illumination and/or
scattering. Warped accretion discs are probably needed for direct illumination
to work in high-luminosity objects, as their geometrically thin inner discs
decrease the amount of direct illumination possible for a flat disc.
