An X-ray bright ERO hosting a type 2 QSO

P. Severgnini, A. Caccianiga, V. Braito, R. Della Ceca, T. Maccacaro, M. Akiyama, F. J. Carrera, M. T. Ceballos, M. J. Page, P. Saracco, M. G. Watson

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16 Citations (Scopus)


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 (F2-10 kev ∼ 10-13 erg s-1 cm-2) extremely red objects (R - K ≥ 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 (∼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 H > 1022 cm-2) QSO (L2-10 kev = 4 × 1045 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 (zX ∼ 2). The presence of a high redshift QSO2 has been finally confirmed through dedicated VLT optical spectroscopic observations (zO = 1.985 ± 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.

Original languageEnglish
Pages (from-to)859-864
Number of pages6
JournalAstronomy and Astrophysics
Issue number3
Publication statusPublished - 2006 Jun


  • Galaxies: active
  • Galaxies: individual: XBS J0216-0435
  • X-rays: galaxies


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