Strong X-ray absorption in a broad absorption line Quasar: PHL 5200

Abstract

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^+2.3×10²³ 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.