Issue |
A&A
Volume 436, Number 1, June II 2005
|
|
---|---|---|
Page(s) | 195 - 208 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20041940 | |
Published online | 20 May 2005 |
A highly-ionized absorber in the X-ray binary 4U 1323-62: A new explanation for the dipping phenomenon
1
The SRON, the National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
2
Observatoire Astronomique de Strasbourg, 11 rue de l'Université, 67000 Strasbourg, France e-mail: boirin@astro.u-strasbg.fr
3
Astrophysics Missions Division, Research and Scientific Support Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
Received:
2
September
2004
Accepted:
15
February
2005
We report the detection of narrow and
X-ray absorption lines at
keV and
keV in the persistent emission of the dipping low-mass X-ray
binary 4U 1323-62 during a 2003 January XMM-Newton observation. These
features are superposed on a broad emission feature centered on
keV. During dipping intervals the equivalent
width of the
feature increases while that of the
feature decreases, consistent with the presence of less strongly
ionized material in the line-of-sight. As observed previously, the
changes in the 1.0–10 keV spectrum during dips are inconsistent
with a simple increase in absorption by cool material. However, the
changes in both the absorption features and the continuum can
be modeled by variations in the properties of an ionized absorber.
No partial covering of any component of the spectrum, and hence no
extended corona, are required. From persistent to deep dipping, the
photo-ionization parameter, ξ, expressed in , decreases
from
of
to
of
, while
the equivalent hydrogen column density of the ionized absorber
increases from (
)
1022 atoms cm-2 to (
)
1022 atoms cm-2. Since
highly-ionized absorption features are seen from many other dip
sources, this mechanism may also explain the overall changes in
X-ray spectrum observed during dipping intervals from these systems.
Key words: accretion, accretion disks / X-rays: individual: 4U 1323-62 / X-rays: general
© ESO, 2005
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