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 keV } \sim 10 ^ { -13 } erg s ^ { -1 } cm ^ { -2 } ) extremely red objects ( R-K \geq 5 ) discovered so far .
The source , XBS J0216-0435 , belongs to the XMM-Newton Bright Serendipitous Survey and it has extreme X–ray–to–optical ( \sim 220 ) and X–ray–to–near–infrared ( \sim 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 _ { H } > 10 ^ { 22 } cm ^ { -2 } ) QSO ( L _ { 2 - 10 keV } =4 \times 10 ^ { 45 } erg s ^ { -1 } ) is determined .
A statistically significant ( \sim 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 K \alpha line at 6.4 keV , a first estimate of the redshift of the source is derived ( z _ { X } \sim 2 ) .
The presence of a high redshift QSO2 has been finally confirmed through dedicated VLT optical spectroscopic observations ( z _ { O } =1.985 \pm 0.002 ) .
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 .