Issue |
A&A
Volume 481, Number 1, April I 2008
Science with Hinode
|
|
---|---|---|
Page(s) | 149 - 159 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20078368 | |
Published online | 04 February 2008 |
1RXS J173021.5-055933: a cataclysmic variable with a fast-spinning magnetic white dwarf*
1
INAF – Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy e-mail: demartino@na.astro.it
2
Dipartimento di Fisica, Universita' degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy e-mail: matt@fis.uniroma3.it
3
CRESST and X-ray Astrophysics Laboratory NASA/GSFC, Greenbelt, MD 20771 and Department of Physics, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA e-mail: mukai@milkyway.gsfc.nasa.gov
4
Service d'Astrophysique, DSM/DAPNIA/SAp, CE Saclay, 91191 Gif-sur-Yvette Cedex, France e-mail: [bonnetbidaud;mfalanga]@cea.fr
5
Department of Physics, University of Warwick, Coventry CV4 7AL, UK e-mail: [boris.gaensicke;Tom.Marsh]@warwick.ac.uk
6
Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße, Postfach 1312, 85741 Garching, Germany e-mail: fwh@mpe.mpg.de
7
Laboratory APC, University Denis Diderot, 10 Rue Alice Domon et Leonie Duquet, 75013 and LUTH, Observatoire de Paris, 92190 Meudon, France e-mail: martine.mouchet@obspm.fr
8
Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK e-mail: [s.littlefair;vik.dhillon]@shef.ac.uk
Received:
27
July
2007
Accepted:
20
January
2008
Aims.We present the first X-ray observations with the XMM-Newton and INTEGRAL satellites of the recently discovered cataclysmic variable 1RXS J173021.5-055933, together with simultaneous UV and coordinated optical photometry aiming at characterising its broad-band temporal and spectral properties and classifying this system as a magnetic one.
Methods.We performed a timing analysis of the X-ray, UV, and optical light curves to identify and to study the energy dependence of the fast 128 s pulsation over a wide energy range. X-ray spectral analysis in the broad 0.2-100 keV X-ray range was performed to characterise the peculiar emission properties of this source.
Results.We find that the X-ray light curve is dominated by the spin period of
the accreting white dwarf in contrast to the far-UV range, which turns out
to be unmodulated at a 3σ level. Near-UV and optical
pulses are instead detected at twice the spin frequency. We identify the contributions from two accreting poles that imply a moderately inclined dipole field allowing, one pole
to dominate at energies at least up to 10 keV, and a secondary
that instead is negligible above 5 keV. X-ray spectral analysis
reveals the presence of multiple emission components consisting of
optically thin plasma with temperatures
ranging from 0.17 keV to 60 keV and a hot blackbody at ~90 eV.
The spectrum is also strongly affected by peculiar absorption
components consisting of two
high-density (~3
and 2
) intervening columns, plus a warm absorber. The last
is detected from an OVII absorption edge at 0.74 keV, which suggests
that photoionization of pre-shock material is also occurring in this system.
Conclusions.The observed properties indicate that the accretor in 1RXS J173021.5-055933 is a white dwarf with a likely weak magnetic field, thus confirming this cataclysmic variable as an intermediate polar (IP) with one of the most extreme spin-to-orbit period ratios. This system also joins the small group of IPs showing a soft X-ray reprocessed component, suggesting that this characteristics is not uncommon in these systems.
Key words: stars: binaries: close / stars: individual: 1RXS J173021.5-055933 / stars: novae, cataclysmic variables / white dwarfs
© ESO, 2008
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