Bibcode
Page, M. J.; Carrera, F. J.; Ceballos, M.; Corral, A.; Ebrero, J.; Esquej, P.; Krumpe, M.; Mateos, S.; Rosen, S.; Schwope, A.; Streblyanska, A.; Symeonidis, M.; Tedds, J. A.; Watson, M. G.
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society, Volume 464, Issue 4, p.4586-4592
Fecha de publicación:
2
2017
Número de citas
4
Número de citas referidas
4
Descripción
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.