Roche tomography of cataclysmic variables - II. Images of the secondary stars in AM Her, QQ Vul, IP Peg and HU Aqr

Watson, C. A.; Dhillon, V. S.; Rutten, R. G. M.; Schwope, A. D.

doi:10.1046/j.1365-8711.2003.06381.x

Cited by 42 publications

(62 citation statements)

References 46 publications

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“…The spread in γ as measured by Roche tomography may be explained by instrumental offsets between different instruments, as well as for the same instrument over different observation periods. Values of γ obtained by using entropy landscapes was found to be independent of the assumed inclination, as previously found by Watson et al (2003Watson et al ( , 2006 and Hill et al (2014). In addition, the values obtained using the radial velocity curves are similar, although these will be biased, as discussed in section 3.…”

Section: Systemic Velocity Inclination and Massessupporting

confidence: 79%

Roche tomography of cataclysmic variables – VII. The long-term magnetic activity of AE Aqr

Hill

Watson²,

Steeghs

et al. 2016

Mon. Not. R. Astron. Soc.

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We present a long-term study of the secondary star in the cataclysmic variable AE Aqr, using Roche tomography to indirectly image starspots on the stellar surface spanning 8 years of observations. The 7 maps show an abundance of spot features at both high and low latitudes. We find that all maps have at least one large high-latitude spot region, and we discuss its complex evolution between maps, as well as its compatibility with current dynamo theories. Furthermore, we see the apparent growth in fractional spot coverage, f s , around 45 • latitude over the duration of observations, with a persistently high f s near latitudes of 20 • . These bands of spots may form as part of a magnetic activity cycle, with magnetic flux tubes emerging at different latitudes, similar to the 'butterfly' diagram for the Sun. We discuss the nature of flux tube emergence in close binaries, as well as the activity of AE Aqr in the context of other stars.

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Section: Systemic Velocity Inclination and Massessupporting

confidence: 79%

Roche tomography of cataclysmic variables – VII. The long-term magnetic activity of AE Aqr

Hill

Watson²,

Steeghs

et al. 2016

Mon. Not. R. Astron. Soc.

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“…However, all optimum RLFFs determined from each independent data set are in close agreement, ranging between 96-98 per cent, and so we can be confident that the measured RLFF and masses are robust. The amount of scatter in the entropy 'parabolas' is consistent with the low SNR of the data being fit -similar scatter was found when performing Roche tomography with relatively low-quality data of the CVs AM Her and QQ Vul (Watson et al 2003).…”

Section: Roche Lobe Filling Factor and Massessupporting

confidence: 66%

“…In previous maps of CVs (e.g. Watson et al 2003) features on this part of the star were attributed to irradiation effects from the white dwarf, where ionisation of the photosphere causes a decrease in photometric flux. However, the features reconstructed here are patchy in morphology, rather than smoothly varying, which suggests that irradiation is not the main contributing factor of the features in this region.…”

Section: Surface Mapsmentioning

confidence: 90%

“…The technique assumes the secondary star rotates synchronously in a circular orbit around the centre of mass, and uses phase-resolved spectral line profiles to map the line-intensity distribution across the star's surface in real space. The method has been extensively applied to the secondary stars in CVs over the last 20 years (Rutten & Dhillon 1994Watson et al 2003;Schwope et al 2004;Watson et al 2006Watson et al , 2007Hill et al 2014), and artefacts arising from systematic errors are well characterised and understood. For a detailed description of the methodology and axioms of Roche tomography, we refer the reader to the references above and the technical reviews by and .…”

Section: Roche Tomographymentioning

confidence: 99%

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The crowded magnetosphere of the post-common-envelope binary QS Virginis

Parsons

Hill

Marsh

et al. 2016

Mon. Not. R. Astron. Soc.

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We present high speed photometry and high resolution spectroscopy of the eclipsing post common envelope binary QS Virginis (QS Vir). Our 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 timescale 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 longlived 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 ± 0.013M ⊙ , and has a radius of 0.01068 ± 0.00007R ⊙ , consistent with evolutionary models. The tidally distorted M star has a mass of 0.382 ± 0.006M ⊙ and a radius of 0.381 ± 0.003R ⊙ , 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 seconds), or due to a weak (∼100kG) 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 its over-inflated we conclude that QS Vir is most likely a pre-cataclysmic binary just about to become semi-detached.

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“…This can be attributed to irradiation from the accretion regions which is shielded from the leading hemisphere by the gas stream and accretion curtain. Likewise, similar irradiation patterns are also evident in Roche tomograms of two more polars, AM Her and QQ Vul (see Watson et al 2003a). …”

Section: Science Highlightssupporting

confidence: 57%

Roche tomography of the secondary stars in CVs

Watson

Dhillon

2004

Astron Nachr

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Abstract. The secondary stars in cataclysmic variables (CVs) are key to our understanding of the origin, evolution and behaviour of this class of interacting binary. In seeking a fuller understanding of these objects, the challenge for observers is to obtain images of the secondary star. This goal can be achieved through Roche tomography, an indirect imaging technique that can be used to map the Roche-lobe-filling secondary. The review begins with a description of the basic principles that underpin Roche tomography, including methods for determining the system parameters. Finally, we conclude with a look at the main scientific highlights to date, including the first unambiguous detection of starspots on AE Aqr B, and consider the future prospects of this technique.

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Roche tomography of cataclysmic variables - II. Images of the secondary stars in AM Her, QQ Vul, IP Peg and HU Aqr

Cited by 42 publications

References 46 publications

Roche tomography of cataclysmic variables – VII. The long-term magnetic activity of AE Aqr

Roche tomography of cataclysmic variables – VII. The long-term magnetic activity of AE Aqr

The crowded magnetosphere of the post-common-envelope binary QS Virginis

Roche tomography of the secondary stars in CVs

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