Strong X-ray Absorption in a BALQSO: PHL5200

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We present ASCA observations of the z=1.98 prototype BALQSO: PHL5200. The source was detected in both SIS and GIS. A power-law spectrum (αₑ = 0.6⁺⁰.⁹₋₀.₆) with large intrinsic absorption (Nₕ = 1.3⁺².³₋₁.₁ × 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 two to three orders of magnitude larger than earlier estimates of column densities in BALQSOs. This implies that the BAL systems are much more highly ionized than previously thought.