UNSPECIFIED. (2006) The X-ray properties of the magnetic cataclysmic variable UU Columbae. ASTRONOMY & ASTROPHYSICS, 454 (1). pp. 287-294. ISSN 0004-6361

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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
Journal or Publication Title:	ASTRONOMY & ASTROPHYSICS
Publisher:	EDP SCIENCES S A
ISSN:	0004-6361
Date:	July 2006
Volume:	454
Number:	1
Number of Pages:	8
Page Range:	pp. 287-294
Identification Number:	10.1051/0004-6361:20065078
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/33348

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