1RXS J173021.5-055933 : a cataclysmic variable with a fast-spinning magnetic white dwarf
De Martino, Domitilla, Matt, Giorgio, Mukai, Koji, Bonnet-Bidaud, Jean-Marc, Falanga, M., Gänsicke, B. T. (Boris T.), Haberl, F., Marsh, T. R., Mouchet, M., Littlefair, S. P. and Dhillon, V. S.. (2008) 1RXS J173021.5-055933 : a cataclysmic variable with a fast-spinning magnetic white dwarf. Astronomy & Astrophysics, Vol.481 (No.1). pp. 149-159. ISSN 0004-6361
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Official URL: http://dx.doi.org/10.1051/0004-6361:20078368
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 × 1021 cm−2 and 2 × 1023 cm−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.
|Item Type:||Journal Article|
|Subjects:||Q Science > QB Astronomy|
|Divisions:||Faculty of Science > Physics|
|Library of Congress Subject Headings (LCSH):||Cataclysmic variable stars, Magnetic stars, X-ray sources, Galactic|
|Journal or Publication Title:||Astronomy & Astrophysics|
|Official Date:||April 2008|
|Page Range:||pp. 149-159|
|Access rights to Published version:||Open Access|
|Funder:||Agenzia spaziale italiana [Italian Space Agency] (ASI), Particle Physics and Astronomy Research Council (Great Britain) (PPARC), Instituto de Astrofísica de Canarias|
|Grant number:||I/023/05/0 (ASI), PP/D002370/1 (PPARC)|
Anders, E., & Grevesse, N. 1989, GeCoA, 53, 197
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