Issue |
A&A
Volume 439, Number 1, August III 2005
|
|
---|---|---|
Page(s) | 287 - 300 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20053017 | |
Published online | 22 July 2005 |
On the nature of the X-ray source in GK Persei
1
Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany e-mail: [svrielmann;jschmitt]@hs.uni-hamburg.de
2
Department of Physics, Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP, UK e-mail: j.ness1@physics.ox.ac.uk
Received:
8
March
2005
Accepted:
28
April
2005
We report XMM-Newton observations of the
intermediate polar (IP) GK Per on the rise to the 2002 outburst and
compare them to Chandra observations during quiescence.
The asymmetric spin light curve implies an asymmetric shape of
a semi-transparent accretion curtain and we propose a model for its
shape. A low Fe xvii (15.01/15.26 Å)
line flux ratio confirms the need for an asymmetric geometry and
significant effects of resonant line scattering.
Medium resolution PN spectra in outburst and ACIS-S
spectra in quiescence can both be fitted with a leaky absorber
model for the post shock hard X-ray emission, a black body
(outburst) for the thermalized X-ray emission from the white dwarf
and an optically thin spectrum. The difference in the leaky
absorber emission between high and low spin as well as
quasi-periodic oscillation (QPO) or flares states can be fully
explained by a variation in the absorbing column density. For the
explanation of the difference between outburst and quiescence a
combination of the variation of the column density and the electron
and ion densities is necessary. The Fe fluorescence at 6.4 keV
with an equivalent width of 447 eV and a possible Compton
scattering contribution in the red wing of the line is not
significantly variable during spin cycle or on QPO periods, i.e. a
significant portion of the line originates in the wide accretion
curtains.
High-resolution RGS spectra reveal a number of emission lines from
H-like and He-like elements. The lines are broader than the
instrumental response with a roughly constant velocity dispersion
for different lines, indicating identical origin. He-like emission
lines are used to give values for the electron densities of
. We do not detect any variation in the emission
lines during the spin cycle, implying that the lines are not
noticeably obscured or absorbed. We conclude that they originate in
the accretion curtains and that accretion might take place from all
azimuths.
Key words: stars: binaries: close / stars: novae, cataclysmic variables / stars: individual: GK Per / X-rays: stars / accretion, accretion disks
© ESO, 2005
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