An Exploratory Chandra Survey of a Well-defined Sample of 35 Large Bright Quasar Survey Broad Absorption Line Quasars

We present 4–7 ks Chandra observations of 35 Broad Absorption Line (BAL) quasars from the Large Bright Quasar Survey, the largest sample of sensitive, 0.5–8.0 keV X-ray observations of this class of quasars to date. The limited ranges in both redshift (z = 1.42–2.90) and ultraviolet luminosity (a factor of ≈ 12) of the sample also make it relatively uniform. Of 35 targets, 27 are detected for a detection fraction of 77%, and we confirm previous studies that find BAL quasars to be generally X-ray weak. Five of the eight non-detections are known low-ionization BAL quasars, confirming reports of extreme X-ray weakness in this subset (∼ 10% of optically selected BAL quasars). Those BAL quasars with the hardest X-ray spectra are also the X-ray weakest, consistent with the interpretation that intrinsic absorption is the primary cause of X-ray weakness in this class of quasars as a whole. Furthermore, the observed trend is not consistent with simple neutral absorption, supporting findings from spectroscopic observations of individual targets that BAL quasars typically exhibit complex X-ray absorption (e.g., partially covering or ionized absorbers). Assuming normal quasar X-ray continua and using the hard-band (observed-frame 2–8 keV) X-ray flux to ‘correct’ for the effects of intrinsic absorption at softer energies increases the relative X-ray-to-optical flux ratios to much closer to the range for normal quasars, further indicating that high-ionization BAL quasars are typically neither intrinsically X-ray weak nor suffer from Compton-thick absorption. In general, we find no evidence for correlations between X-ray weakness and ultraviolet absorption-line properties, with the exception of a likely correlation between the maximum outflow velocity of C IV absorption and the magnitude of X-ray weakness. We discuss the implications of our results for disk-wind models of BAL outflows in quasars. Subject headings: galaxies: active — quasars: absorption lines — X-rays: galaxies