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Properties of X-ray-selected broad absorption-line quasars

Blustin, AJ; Dwelly, T; Page, MJ; McHardy, IM; Seymour, N; Kennea, JA; ... Sekiguchi, K; + view all (2008) Properties of X-ray-selected broad absorption-line quasars. Monthly Notices of the Royal Astronomical Society , 390 (3) 1229 - 1240. 10.1111/j.1365-2966.2008.13825.x. Green open access

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Abstract

Broad absorption-line quasars (commonly termed BALQSOs) contain the most dramatic examples of active galactic nucleus (AGN) driven winds. The high absorbing columns in these winds, ∼1024 cm−2, ensure that BALQSOs are generally X-ray faint. This high X-ray absorption means that almost all BALQSOs have been discovered through optical surveys, and so what little we know about their X-ray properties is derived from very bright optically selected sources. A small number of X-ray-selected BALQSOs (XBALQSOs) have, however, recently been found in deep X-ray survey fields. In this paper we investigate the X-ray and rest-frame ultraviolet (UV) properties of five XBALQSOs for which we have obtained XMM–Newton EPIC X-ray spectra and deep optical imaging and spectroscopy. We find that, although the XBALQSOs have an αox steeper by ∼0.5 than normal QSOs, their median αox is nevertheless flatter by 0.30 than that of a comparable sample of optically selected BALQSOs (OBALQSOs). We rule out the possibility that the higher X-ray to optical flux ratio is due to intrinsic optical extinction. We find that the amount of X-ray and UV absorption due to the wind in XBALQSOs is similar, or perhaps greater than, the corresponding wind absorption in OBALQSOs, so the flatter αox cannot be a result of weaker wind absorption. We conclude that these XBALQSOs have intrinsically higher X-ray to optical flux ratios than the OBALQSO sample with which we compare them.

Type:Article
Title:Properties of X-ray-selected broad absorption-line quasars
Open access status:An open access version is available from UCL Discovery
DOI:10.1111/j.1365-2966.2008.13825.x
Publisher version:http://dx.doi.org/10.1111/j.1365-2966.2008.13825.x
Language:English
Additional information:© 2008 RAS Definitive versions of articles pre-2013 are available at http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-2966, now published by http://mnras.oxfordjournals.org
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Space and Climate Physics

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