Cristian Vignali

TL;DR: In this article, Chandra observations of 10 $z>6$ QSOs, selected to have virial black-hole mass estimates from Mg II line spectroscopy, were used to investigate the X-ray properties of the QSO population in the first Gyr of the Universe, focusing in particular on the $L_{UV}-L_{X}$ relation, which is traced by the $\alpha_{ox}$ parameter, and the shape of their Xray spectra.

TL;DR: The BeppoSAX observations of the bright Narrow-line Seyfert 1 galaxy Ark 564 are presented along with a high quality optical spectrum taken at the 1.5m telescope at La Silla.

TL;DR: In this paper, the L X −L UV relation was studied for a sample of quasars in the redshift range 4' or XMM-Newton, for which a full spectral analysis was performed, determining the rest-frame 2 keV flux density, as well as more general X-ray properties such as the estimate of photon index, and the soft (0.5 −2 keV) and hard (2 −10 keV ) unabsorbed luminosities.

TL;DR: In this paper, an obscured QSO at z = 1.593 was detected in the CO(5-4) transition and in the 1.3mm continuum, with both emissions confined in the central (<4 kpc) radius area.

TL;DR: In this paper, the authors present the version of the point source catalogue of the XXL Survey that was used, in part, in the first series of XXL papers, and present the basic properties of the X-ray point sources and their counterparts.