An X-ray bright ERO hosting a type 2 QSO

We present the XMM-Newton and the optical-VLT spectra along with the optical and the near-infrared photometric data of one of the brightest X-ray ($F_{2{-}10~\rm keV}\sim10^{-13}$ erg s-1 cm-2) extremely red objects ($R-K\ge5$) discovered so far. The source, XBS J0216-0435, belongs to the XMM-Newton Bright Serendipitous Survey and it has extreme X-ray-to-optical (~220) and X-ray-to-near-infrared (~60) flux ratios. Thanks to its brightness, the X-ray statistics are good enough for an accurate spectral analysis by which the presence of an X-ray obscured ($N_{\rm H}>10^{22}$ cm-2) QSO ($L_{2{-}10~\rm keV}=4\times10^{45}$ erg s-1) is determined. A statistically significant (~99%) excess around 2 keV in the observed-frame suggests the presence of an emission line. By assuming that this feature corresponds to the iron Kα line at 6.4 keV, a first estimate of the redshift of the source is derived ($z_{\rm X}\sim2$). The presence of a high redshift QSO2 has been finally confirmed through dedicated VLT optical spectroscopic observations ($z_{\rm O}=1.985\pm0.002$). This result yields to an optical validation of a new X-ray Line Emitting Object (XLEO) for which the redshift has been firstly derived from the X-ray data. XBS J0216-0435 can be considered one of the few examples of X-ray obscured QSO2 at high redshift for which a detailed X-ray and optical spectral analysis has been possible. The spectral energy distribution from radio to X-rays is also presented. Finally from the near-infrared data the luminosity and the stellar mass of the host galaxy has been estimated finding a new example of the coexistence at high-z between massive galaxies and powerful QSOs.