X-Ray Spectroscopy of Quasi-Stellar Objects with Broad Ultraviolet Absorption Lines

For the population of quasi-stellar objects (QSOs) with broad ultraviolet absorption lines, we are just beginning to accumulate X-ray observations with enough counts for spectral analysis at CCD resolution. From a sample of eight QSOs (including four broad absorption line [BAL] QSOs and three mini-BAL QSOs) with ASCA or Chandra spectra with more than 200 counts, general patterns are emerging. Their power-law X-ray continua are typical of normal QSOs with Γ ≈ 2.0, and the signatures of a significant column density [N_H ≈ (0.1-4) × 10²³ cm^-2] of intrinsic, absorbing gas are clear. Correcting the X-ray spectra for intrinsic absorption recovers a normal ultraviolet-to-X-ray flux ratio, indicating that the spectral energy distributions of this population are not inherently anomalous. In addition, a large fraction of our sample shows significant evidence for complexity in the absorption. The subset of BAL QSOs with broad Mg II absorption apparently suffers from Compton-thick absorption completely obscuring the direct continuum in the 2-10 keV X-ray band, complicating any measurement of their intrinsic X-ray spectral shapes.