Related papers: The HELLAS2XMM survey: VI. X-ray absorption in the…

We have measured the X-ray spectral properties of a complete flux-limited sample of bright AGNs from HEAO-1 all-sky catalogs to investigate their statistics and provide greater constraints on the bright-end of the hard X-ray luminosity…

This paper presents the analysis of a statistically complete sample of 28 serendipitous X-ray sources selected in 82 pointed XMM-Newton fields down to a count-rate of 0.002 counts s^-1(4.5-7.5 keV energy band). This is the first sample…

We present the X-ray spectral analysis of the 1855 extragalactic sources in the Chandra COSMOS-Legacy survey catalog having more than 30 net counts in the 0.5-7 keV band. 38% of the sources are optically classified Type 1 active galactic…

X-rays provide a robust method in identifying AGN. However, in the high-redshift Universe, their space density is relatively low, and, in combination with the small areas covered by X-ray surveys, the selected AGN are poorly sampled. Deep…

We present results on a search of heavily obscured active galaxies z>1.7 using the rest-frame 9-20 keV excess for X-ray sources detected in the deep XMM-CDFS survey. Out of 176 sources selected with the conservative detection criteria (>8…

Our goal is to probe the populations of obscured and unobscured AGN investigating their optical-IR and X-ray properties as a function of X-ray flux, luminosity and redshift within a hard X-ray selected sample of 136 X-ray sources in the XMM…

X-ray extragalactic surveys are ideal laboratories for the study of the evolution and clustering of active galactic nuclei (AGN). The XXL Survey spans two fields of a combined 50 $deg^2$ observed for more than 6Ms with XMM-Newton, occupying…

We present results from the photometric and spectroscopic identification of 122 X-ray sources recently discovered by XMM-Newton in the 2-10 keV band (the HELLAS2XMM 1dF sample). Their flux cover the range 8E-15-4E-13 cgs and the total area…

We present the results of optical spectroscopic identifications of a bright subsample of 2-10keV hard X-ray selected sources from the ASCA Medium Sensitivity Survey in the northern sky. The flux limit of the subsample is 3*10^-13 erg s^-1…

We present an analysis of the X-ray spectral properties of 61 hard X-ray selected (2-8 keV) sources from the bright ($f_{2-8 keV}>10^{-14}$ \funits) {\it XMM-Newton}/2dF survey. This comprises of 9 {\it XMM-Newton} pointings in the North…

We combine bright XMM data with the Chandra Deep Field South observations in order to explore the behavior of the intrinsic AGN absorption, as a function of redshift and luminosity.Our sample consists of 359 sources selected in the hard 2-8…

We report on the results of a detailed analysis of the X-ray spectral properties of a large sample of sources detected serendipitously with the XMM-Newton observatory in 25 selected fields. The survey covers a total solid angle of ~3.5 deg2…

We explore the X-ray properties of optically selected QSOs spectroscopically identified in the course of the 2dF QSO survey (2QZ). Our main goal is to expand to higher redshifts previous findings suggesting the presence of a fraction of…

We discuss the spectral analysis of a sample of 63 Active Galactic Nuclei (AGN) detected above a limiting flux of $S(8-24$ keV$)=7\times10^{-14}$ erg/s/cm$^2$ in the multi-tiered NuSTAR Extragalactic Survey program. The sources span a…

We present a method for the identification of heavily absorbed AGN (NH>10^23 cm^-2) from X-ray photometric data. We do this using a set of XMM-Newton reference spectra of local galaxies for which we have accurate NH information, as…

(Abridged) We present the results of the photometric and spectroscopic identification of 110 hard X-ray selected sources (6e-15<F(2-10 keV)<4e-14 cgs) from 5 additional XMM-Newton fields, nearly doubling the original HELLAS2XMM sample. We…

We have used very deep XMM-Newton observations of the Chandra Deep Field-South to examine the spectral properties of the faint active galactic nucleus (AGN) population. Crucially, redshift measurements are available for 84% (259/309) of the…

We perform a detailed investigation of moderate-to-high quality X-ray spectra of ten of the most luminous active galactic nuclei (AGNs) known at z>4 (up to z~6.28). This study includes five new XMM observations and five archived X-ray…

We present optical and X-ray data for a sample of serendipitous XMM-Newton sources that are selected to have 0.5-2 keV vs 2-4.5 keV X-ray hardness ratios which are harder than the X-ray background. The sources have 2-4.5 keV X-ray flux >=…

We report on the spectral properties of a sample of 90 hard X-ray selected serendipitous sources detected in 12 XMM observations with 1<F(2-10)<80 10^(-14) erg/cm2/s. Approximately 40% of the sources are optically identified with 0.1<z<2…