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Kinematics of the ultracompact helium accretor AM canum venaticorum

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Roelofs, Gijs H. A., Groot, P. J. (Paul J.), Nelemans, G., Marsh, T. R. and Steeghs, D. (Danny), 1972-. (2006) Kinematics of the ultracompact helium accretor AM canum venaticorum. Monthly Notices of the Royal Astronomical Society, Vol.371 (No.3). pp. 1231-1242. ISSN 0035-8711

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Official URL: http://dx.doi.org/10.1111/j.1365-2966.2006.10718.x

Abstract

We report on the results from a five-night campaign of high-speed spectroscopy of the 17-min binary AM Canum Venaticorum (AM CVn), obtained with the 4.2-m William Herschel Telescope on La Palma. We detect a kinematic feature that appears to be entirely analogous to the 'central spike' known from the long-period, emission-line AM CVn stars GP Com, V396 Hya and SDSS J124058.03-015919.2, which has been attributed to the accreting white dwarf. Assuming that the feature indeed represents the projected velocity amplitude and phase of the accreting white dwarf, we derive a mass ratio q = 0.18 +/- 0.01 for AM CVn. This is significantly higher than the value found in previous, less direct measurements. We discuss the implications for AM CVn's evolutionary history and show that a helium star progenitor scenario is strongly favoured. We further discuss the implications for the interpretation of AM CVn's superhump behaviour, and for the detectability of its gravitational-wave signal with the Laser Interferometer Space Antenna (LISA). In addition, we demonstrate a method for measuring the circularity or eccentricity of AM CVn's accretion disc, using stroboscopic Doppler tomography. We test the predictions of an eccentric, precessing disc that are based on AM CVn's observed superhump behaviour. We limit the effective eccentricity in the outermost part of the disc, where the resonances that drive the eccentricity are thought to occur, to e = 0.04 +/- 0.01, which is smaller than previous models indicated.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Double stars, White dwarf stars
Journal or Publication Title:	Monthly Notices of the Royal Astronomical Society
Publisher:	Wiley-Blackwell Publishing, Inc
ISSN:	0035-8711
Date:	21 September 2006
Volume:	Vol.371
Number:	No.3
Number of Pages:	12
Page Range:	pp. 1231-1242
Identification Number:	10.1111/j.1365-2966.2006.10718.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 (NWO), 639.041.405 (NWO)
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URI:	http://wrap.warwick.ac.uk/id/eprint/33092