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An evolved donor star in the long-period cataclysmic variable HS 0218+3229

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Rodríguez-Gil, P., Torres, M. A. P., Gänsicke, B. T. (Boris T.), Muñoz-Darias, T., Steeghs, D. (Danny), 1972-, Schwarz, R. (Robert), Rau, Arne and Hagen, H.-J.. (2009) An evolved donor star in the long-period cataclysmic variable HS 0218+3229. Astronomy & Astrophysics, Vol.496 (No.3). pp. 805-812. ISSN 0004-6361

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Official URL: http://dx.doi.org/10.1051/0004-6361/200811312

Abstract

Context. We present time-resolved spectroscopy and photometry of HS 0218+3229, a new long-period cataclysmic variable discovered within the Hamburg Quasar Survey. It is one of the few systems that allow a dynamical measurement of the masses of the stellar components. Aims. We combine the analysis of time-resolved optical spectroscopy and R-band photometry with the aim of measuring the mass of the white dwarf and the donor star and the orbital inclination. Methods. Cross-correlation of the spectra with K-type dwarf templates is used to derive the radial velocity curve of the donor star. An optimal subtraction of the broadened templates is performed to measure the rotational broadening and constrain the spectral type of the donor. Finally, an ellipsoidal model is fitted to the R-band light curve to obtain constraints upon the orbital inclination of the binary system. Results. The orbital period of HS 0218+3229 is found to be 0.297229661 ± 0.000000001 d (7.13351186 ± 0.00000002 h), and the amplitude of the donor’s radial velocity curve is K2 = 162.4 ± 1.4 kms−1. Modelling the ellipsoidal light curves gives an orbital inclination in the range i = 59◦ ±3◦. A rotational broadening between 82.4±1.2 km s−1 and 89.4±1.3 km s−1 is found when assuming zero and continuum limb darkening, respectively. The secondary star has most likely a spectral type K5 and contributes ∼80–85% to the R-band light. Our analysis yields a mass ratio of 0.52 < q < 0.65, a white dwarf mass of 0.44 < M1(M) < 0.65, and a donor star mass of 0.23 < M2(M) < 0.44. Conclusions. We find that the donor star in HS 0218+3229 is significantly undermassive for its spectral type. It is therefore very likely that it has undergone nuclear evolution prior to the onset of mass transfer.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Cataclysmic variable stars, Double stars -- Masses, Double stars -- Orbits, Accretion (Astrophysics)
Journal or Publication Title:	Astronomy & Astrophysics
Publisher:	EDP Sciences
ISSN:	0004-6361
Date:	March 2009
Volume:	Vol.496
Number:	No.3
Page Range:	pp. 805-812
Identification Number:	10.1051/0004-6361/200811312
Status:	Peer Reviewed
Access rights to Published version:	Open Access
Funder:	XMM-Newton Observatory, Deutsche Forschungsgemeinschaft (DFG)
Grant number:	NNG05GJ22G (XMM-Newton), Re 353/11 (DFG), Re 353/22 (DFG)
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URI:	http://wrap.warwick.ac.uk/id/eprint/3432