Strong X-Ray Absorption in a Broad Absorption Line Quasar: PHL 5200

We present ASCA observations of the z = 1.98 prototype broad absorption line quasar (BALQSO): PHL 5200. The source was detected in both SIS and GIS. A power-law spectrum (α E = 0.6 −0.6 +0.9 ) with large intrinsic absorption ( N H = 1.3 −1.1 +2.3 × 10 23 cm -2 ) best describes the spectrum. Excess column density over the local Galactic value is required at the 99% confidence level. This detection suggests that, although BALQSOs are X-ray-quiet, it is strong absorption in the BAL region that makes them appear faint to low-energy X-ray experiments. The required intrinsic absorbing column density is 2-3 orders of magnitude larger than earlier estimates of column densities in BALQSOs. This implies that the BAL systems are much more highly ionized than was previously thought.