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The X-ray properties of the magnetic cataclysmic variable UU Columbae
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de Martino, D., Matt, Giorgio, Mukai, K., Bonnet-Bidaud, Jean-Marc, Burwitz, V., Gänsicke, B. T. (Boris T.), Haberl, F. and Mouchet, M. (2006) The X-ray properties of the magnetic cataclysmic variable UU Columbae. Astronomy & Astrophysics, 454 (1). pp. 287-294. doi:10.1051/0004-6361:20065078 ISSN 0004-6361.
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Official URL: http://dx.doi.org/10.1051/0004-6361:20065078
Abstract
Aims. XMM-Newton observations to determine for the first time the broad-band X-ray properties of the faint, high galactic latitude intermediate polar UUCol are presented.
Methods. We performed X-ray timing analysis in different energy ranges of the EPIC cameras, which reveals the dominance of the 863 s white dwarf rotational period. The spin pulse is strongly energy dependent. Weak variabilities at the beat 935 s and at the 3.5 h orbital periods are also observed, but the orbital modulation is detected only below 0.5 keV. Simultaneous UV and optical photometry shows that the spin pulse is anti-phased with respect to the hard X-rays. Analysis of the EPIC and RGS spectra reveals the complexity of the X-ray emission, which is composed of a soft 50 eV black-body component and two optically thin emission components at 0.2 keV and 11 keV strongly absorbed by dense material with an equivalent hydrogen column density of 10(23) cm(-2) that partially (50%) covers the X-ray source.
Results. The complex X-ray and UV/optical temporal behaviour indicates that accretion occurs predominantly (similar to 80%) via a disc with a partial contribution (similar to 20%) directly from the stream. The main accreting pole dominates at high energies whilst the secondary pole mainly contributes in the soft X-rays and at lower energies. The bolometric flux ratio of the soft-to-hard X-ray emissions is found to be consistent with the prediction of the standard accretion shock model. We find the white dwarf in UUCol accretes at a low rate and possesses a low magnetic moment. It is therefore unlikely that UUCol will evolve into a moderate field strength polar, so that the soft X-ray intermediate polars still remain an enigmatic small group of magnetic cataclysmic variables.
| Item Type: | Journal Article | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Subjects: | Q Science > QB Astronomy | ||||||||
| Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||
| Journal or Publication Title: | Astronomy & Astrophysics | ||||||||
| Publisher: | EDP Sciences | ||||||||
| ISSN: | 0004-6361 | ||||||||
| Official Date: | 4 July 2006 | ||||||||
| Dates: |
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| Volume: | 454 | ||||||||
| Number: | 1 | ||||||||
| Number of Pages: | 8 | ||||||||
| Page Range: | pp. 287-294 | ||||||||
| DOI: | 10.1051/0004-6361:20065078 | ||||||||
| Status: | Peer Reviewed | ||||||||
| Publication Status: | Published | ||||||||
| Access rights to Published version: | Open Access (Creative Commons) |
Data sourced from Thomson Reuters' Web of Knowledge
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