Strong X-ray Absorption in a Broad Absorption Line Quasar: Phl 5200

We present ASCA observations of the z 5 1.98 prototype broad absorption line quasar (BALQSO): PHL 5200. The source was detected in both SIS and GIS. A power-law spectrum (aE 5 0.620.6 10.9 ) with large intrinsic absorption (NH 5 1.321.1 12.3 3 10 cm) 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. Subject headings: quasars: absorption lines— quasars: individual (PHL 5200)—X-rays: galaxies