HEAD 2000, November 2000
Session 2. Active Galaxies
Display, Monday, November 6, 2000, 8:00am-6:00pm, Bora Bora Ballroom

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[2.04] Lifting the Shroud Around Broad Absorption Line QSOs: A Chandra Survey

T. Aldcroft, P.J. Green, B.J. Wilkes, M. Elvis (SAO), S. Mathur (OSU)

We have carried out a short-exposure Chandra survey of a sample of 10 bright Broad Absorption Line (BAL) QSOs. BALs are caused by outflows from the nucleus with velocities reaching 0.2c. Recent ROSAT studies imply that the soft X-ray continuum of BALQSOs is either a) strongly absorbed by highly ionized material, or b) intrinsically underluminous. Since about 10% of QSOs show BALs, the former interpretation supports the hypothesis that most QSOs contain BAL-type outflows, with a 10% covering factor. BALQSOs may thus provide a unique probe of cloud conditions near the nucleus of most QSOs.

Our snapshot survey consists of 10 observations ranging in length from 1.0 to 5.5 ksec, depending on the predicted X-ray source brightness. The total observation time is 36 ksec. Eight out of ten sources are detected, with observed counts ranging from ~0 to ~100 each. For the detected quasars, the observed optical to X-ray spectral slope (\alphaox from 4400\,Å\ to 2\,keV) varies from 2 to 2.5, with an average value of 2.3. In this paper we present details of these observations, analysis of the composite X-ray spectrum from the survey, and the implications of our data on the true nature of BALQSOs.

This work was supported by NASA grant NAS8-39073.

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