Parsons, S. G., Hill, C. A., Marsh, T. R., Gänsicke, B. T. (Boris T.), Watson, C. A., Steeghs, D., Dhillon, V. S., Littlefair, S. P., Copperwheat, C. M., Schreiber, M. R. and Zorotovic, M. (2016) The crowded magnetosphere of the post-common-envelope binary QS Virginis. Monthly Notices of the Royal Astronomical Society, 458 (3). pp. 2793-2812. doi:10.1093/mnras/stw516

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Abstract

We present high-speed photometry and high-resolution spectroscopy of the eclipsing post-common-envelope binary QS Virginis (QS Vir). Our Ultraviolet and Visual Echelle Spectrograph (UVES) spectra span multiple orbits over more than a year and reveal the presence of several large prominences passing in front of both the M star and its white dwarf companion, allowing us to triangulate their positions. Despite showing small variations on a time-scale of days, they persist for more than a year and may last decades. One large prominence extends almost three stellar radii from the M star. Roche tomography reveals that the M star is heavily spotted and that these spots are long-lived and in relatively fixed locations, preferentially found on the hemisphere facing the white dwarf. We also determine precise binary and physical parameters for the system. We find that the 14 220 ± 350 K white dwarf is relatively massive, 0.782 ± 0.013 M⊙, and has a radius of 0.010 68 ± 0.000 07 R⊙, consistent with evolutionary models. The tidally distorted M star has a mass of 0.382 ± 0.006 M⊙ and a radius of 0.381 ± 0.003 R⊙, also consistent with evolutionary models. We find that the magnesium absorption line from the white dwarf is broader than expected. This could be due to rotation (implying a spin period of only ˜700 s), or due to a weak (˜100 kG) magnetic field, we favour the latter interpretation. Since the M star's radius is still within its Roche lobe and there is no evidence that it is overinflated, we conclude that QS Vir is most likely a pre-cataclysmic binary just about to become semidetached.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	White dwarf stars , Eclipsing binaries
Journal or Publication Title:	Monthly Notices of the Royal Astronomical Society
Publisher:	Oxford University Press
ISSN:	0035-8711
Official Date:	21 May 2016
Dates:	Date Event 21 May 2016 Published 16 November 2015 Available 1 March 2016 Accepted 1 March 2016 Submitted
Volume:	458
Number:	3
Page Range:	pp. 2793-2812
DOI:	10.1093/mnras/stw516
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Open Access
Funder:	Fondo Nacional de Desarrollo Científico y Tecnológico (Chile) (FONDECYT), Queen's University of Belfast, Science and Technology Facilities Council (Great Britain) (STFC), Seventh Framework Programme (European Commission) (FP7), Chile. Ministerio de Economía, European Southern Observatory (ESO)
Grant number:	3140583130559, 1100782 (FONDECYT), ST/L000733 (STFC), 320964 WDTracer (FP7), IDs 090.D-0277, IDs 093.D-0096 (ESO)

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