Issue |
A&A
Volume 379, Number 2, November IV 2001
|
|
---|---|---|
Page(s) | 540 - 550 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20011322 | |
Published online | 15 November 2001 |
An XMM-Newton study of the X-ray binary MXB 1659-298 and the discovery of narrow X-ray absorption lines
Space Science Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
Corresponding author: L. Sidoli, sidoli@ifctr.mi.cnr.it
Received:
23
July
2001
Accepted:
17
September
2001
We report the discovery of narrow X-ray absorption lines from the
low-mass X-ray binary MXB 1659-298 during an XMM-Newton observation in
2001 February. The 7.1 hr orbital cycle is clearly evident
with narrow X-ray eclipses preceded by intense dipping activity.
A sinusoid-like OM B-band modulation with a peak-to-peak
modulation of ~0.5 mag and a minimum coincident with the
X-ray eclipse is visible.
EPIC and RGS spectra reveal the presence of narrow
resonant absorption features identified with O viii 1s-2p, 1s-3p and
1s-4p,
Ne x 1s-2p, Fe xxv 1s-2p, and Fe xxvi 1s-2p transitions,
together with a broad Fe emission feature at keV.
The equivalent widths of the Fe
absorption features show no obvious dependence on orbital phase,
even during dipping intervals. The equivalent widths of the other
features are consistent with having the same values during persistent
and dipping intervals.
Previously, the only X-ray binaries known to exhibit narrow X-ray absorption
lines were two superluminal jet sources and it had been suggested that
these features are related to the jet formation mechanism. This now
appears unlikely, and instead their presence may be
related to the viewing angle of the system.
The MXB 1659-298 0.6-12 keV continuum is modeled using
absorbed cutoff power-law and blackbody components. During dips the
blackbody is more strongly absorbed than the power-law.
The spectral shape of the 3.6% of
keV emission that
remains during eclipses
is consistent with that during non-dipping intervals.
Key words: accretion, accretion disks / stars: individual: MXB 1659-298 / stars: neutron / X-rays: general
© ESO, 2001
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