Page, MJ;
Carrera, FJ;
Ceballos, M;
Corral, A;
Ebrero, J;
Esquej, P;
Krumpe, M;
... Watson, MG; + view all
(2017)
X-ray-selected broad absorption line quasi-stellar objects.
Monthly Notices of the Royal Astronomical Society
, 464
(4)
pp. 4586-4592.
10.1093/mnras/stw2560.
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Abstract
We study a sample of six X-ray-selected broad absorption line (BAL) quasi-stellar objects (QSOs) from the XMM–Newton Wide Angle Survey. All six objects are classified as BALQSOs using the classic balnicity index, and together they form the largest sample of X-ray-selected BALQSOs. We find evidence for absorption in the X-ray spectra of all six objects. An ionized absorption model applied to an X-ray spectral shape that would be typical for non-BAL QSOs (a power law with energy index α = 0.98) provides acceptable fits to the X-ray spectra of all six objects. The optical to X-ray spectral indices, αOX, of the X-ray-selected BALQSOs, have a mean value of 〈αOX〉 = 1.69 ± 0.05, which is similar to that found for X-ray-selected and optically selected non-BAL QSOs of a similar ultraviolet luminosity. In contrast, optically selected BALQSOs typically have much larger αOX and so are characterized as being X-ray weak. The results imply that X-ray selection yields intrinsically X-ray bright BALQSOs, but their X-ray spectra are absorbed by a similar degree to that seen in optically selected BALQSO samples; X-ray absorption appears to be ubiquitous in BALQSOs, but X-ray weakness is not. We argue that BALQSOs sit at one end of a spectrum of X-ray absorption properties in QSOs related to the degree of ultraviolet absorption in C iv 1550 Å.
| Type: | Article |
|---|---|
| Title: | X-ray-selected broad absorption line quasi-stellar objects |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1093/mnras/stw2560 |
| Publisher version: | https://doi.org/10.1093/mnras/stw2560 |
| Language: | English |
| Additional information: | This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society, copyright © 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. |
| Keywords: | quasars: absorption lines, X-rays: galaxies |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery.ucl.ac.uk/id/eprint/1521314 |
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