De Martino, Domitilla, Bonnet-Bidaud, Jean-Marc, Mouchet, M., Gaensicke, B. T. (Boris T.), Haberl, F. and Motch, C. (2006) The long period intermediate polar 1RXS J154814.5-452845. Astronomy & Astrophysics, Vol.449 (No.3). pp. 1151-1160. doi:10.1051/0004-6361:20053877

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Abstract

We present the first time resolved medium resolution optical spectroscopy of the recently identified peculiar Intermediate Polar (IP)1RXS J154814.5-452845, which allows us to precisely determine the binary orbital period (P Ω = 9.87 ± 0.03 h) and the white dwarf spin period (P ω = 693.01
± 0.06 s). This system is then the third just outside the purported ∼6–10 h IP orbital period gap and the fifth of the small group of long period IPs, which has a relatively high degree of asynchronism. From the presence of weak red absorption features, we identify the secondary star with a spectral type K2 ± 2 V, which appears to have evolved on the nuclear timescale. From the orbital radial velocities of
emission and the red absorption lines a mass ratio q = 0.65
± 0.12 is found. The masses of the components are estimated to be M WD ≥ 0.5 M and M sec = 0.4−0.79 M and the binary inclination 25 ◦ < i ≤ 58 ◦ . A distance between 540–840 pc is estimated. At this distance, the presence of peculiar absorption features surrounding Balmer emissions cannot be due to the contribution of the white dwarf photosphere and their spin modulation suggests an origin in the magnetically confined accretion flow. The white dwarf is also not accreting at a particularly high rate(. M < 5 × 10
16 g s −1 ), for its orbital period. The spin-to-orbit period ratio P ω /P Ω = 0.02 and the low mass accretion rate suggest that this system is far from spin equilibrium. The magnetic moment of the accreting white dwarf is found to be µ < 4.1 × 10 32 G cm 3, indicating a low magnetic
field system.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Cataclysmic variable stars, X-ray sources, Galactic, Accretion (Astrophysics), Stars -- Magnetic fields
Journal or Publication Title:	Astronomy & Astrophysics
Publisher:	EDP Sciences
ISSN:	0004-6361
Official Date:	April 2006
Dates:	Date Event April 2006 Published
Volume:	Vol.449
Number:	No.3
Page Range:	pp. 1151-1160
DOI:	10.1051/0004-6361:20053877
Status:	Peer Reviewed
Access rights to Published version:	Open Access
Funder:	Italy. Ministero dell'istruzione, dell'università e della ricerca (MIUR), Particle Physics and Astronomy Research Council (Great Britain) (PPARC)

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