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On the orbital periods of the AM CVn stars HP Librae and V803 Centauri

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Roelofs, Gijs H. A., Groot, P. J. (Paul J.), Nelemans, G., Marsh, T. R. and Steeghs, D. (Danny), 1972-. (2007) On the orbital periods of the AM CVn stars HP Librae and V803 Centauri. Monthly Notices of the Royal Astronomical Society, Vol.379 (No.1). pp. 176-182. ISSN 0035-8711

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Official URL: http://dx.doi.org/10.1111/j.1365-2966.2007.11931.x

Abstract

We analyse high time resolution spectroscopy of the AM CVn stars HP Librae and V803 Centauri, taken with the New Technology Telescope (NTT) and the Very Large Telescope (VLT) of the European Southern Observatory, Chile.

We present evidence that the literature value for V803 Cen's orbital period is incorrect, based on an observed 'S-wave' in the binary's spectrogram. We measure a spectroscopic period P-V803 (Cen) = 1596.4 +/- 1.2 s of the S-wave feature, which is significantly shorter than the 1611 -s periods found in previous photometric studies. We conclude that the latter period likely represents a 'superhump'. If one assumes that our S-wave period is the orbital period, V803 Cen's mass ratio can be expected to be much less extreme than previously thought, at q similar to 0.07 rather than q similar to 0.016. This relaxes the constraints on the masses of the components considerably: the donor star then does not need to be fully degenerate, and the mass of the accreting white dwarf no longer has to be very close to the Chandrasekhar limit.

For HP Lib, we similarly measure a spectroscopic period P-HP (Lib) = 1102. +/- 8 0.2 s. This supports the identification of HP Lib's photometric periods found in the literature, and the constraints upon the masses derived from them.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Cataclysmic variable stars
Journal or Publication Title:	Monthly Notices of the Royal Astronomical Society
Publisher:	Wiley
ISSN:	0035-8711
Official Date:	21 July 2007
Volume:	Vol.379
Number:	No.1
Number of Pages:	7
Page Range:	pp. 176-182
Identification Number:	10.1111/j.1365-2966.2007.11931.x
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Nederlandse Organisatie voor Wetenschappelijk Onderzoek [Netherlands Organisation for Scientific Research] (NWO), Smithsonian Astrophysical Observatory, Particle Physics and Astronomy Research Council (Great Britain) (PPARC)
Grant number:	639.042.201.DS (NWO), 639.041.405.TRM (NWO)
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URI:	http://wrap.warwick.ac.uk/id/eprint/31734