Doppler imaging of stellar surface structure

Strassmeier, K. G.; Rice, J. B.

doi:10.1051/0004-6361:20021789

Cited by 46 publications

(68 citation statements)

References 36 publications

(38 reference statements)

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“…We conclude that there is significant spot coverage on the inner hemisphere (white dwarf facing side of the M star) observed on all maps. This spot distribution -where there is a higher density of spots on the hemisphere facing the companion star -is similar to that observed in many other systems, such as the pre-CV V471 Tau (Hussain et al 2006), the eclipsing binary ER Vul (Xiang et al 2015), and the close binary σ 2 CrB (Strassmeier & Rice 2003). Furthermore, Kriskovics et al (2013) suggested that the hot-spots mapped on the companion-facing hemisphere in V824 Ara may indicate the strong interaction between the magnetic fields of the component stars, as is commonly observed in close RS CVn-type binaries.…”

Section: Surface Mapssupporting

confidence: 84%

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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Section: Surface Mapssupporting

confidence: 84%

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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“…At the same time the cool polar spot had a large appendage near the phase of conjunction with the secondary behind in 1996/97, but less determinable in 1997/98. A comparable spot dependency on orbital location was seen on the active close binary σ 2 CrB (Strassmeier & Rice 2004). σ 2 CrB is a F9+G0 ZAMS binary.…”

Section: Discussionmentioning

confidence: 52%

Doppler imaging of stellar surface structure

Kővári

Bartus

Strassmeier

et al. 2006

A&A

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Aims. We present the first Doppler images of the bright RS CVn-type binary ζ And. The star is a magnetically active K1 giant with its rotation synchronized to the 17.8-day orbital period. Our revised lithium abundance of log n = 1.2 places ζ And in the vicinity of Li-rich RGB stars but it is nevertheless a Li-normal chromospherically active binary star. The star seems to undergo its first standard dredge-up dilution. Methods. Four consecutive Doppler images were obtained from a continuous 67-night observing run at NSO-McMath in 1996/97. An additional single image was obtained from a continuous 19-night run at KPNO in 1997/98. These unique data allow to compute a small time series of the evolution of the star's surface structure. All line-profile inversions are done with a modified TempMap version that takes into account the non-spherical shape of the star. Representative test reconstructions are performed and demonstrate the code's reliability and robustness. Results. High and low-latitude spot activity was recovered together with an asymmetric polar cap-like feature. The latter dominated the first half of the two-month time series in 1996/97. The second half showed mostly medium-to-high latitude activity and only a fainter polar spot. The coolest areas were restored with a temperature contrast of about 1000 ± 200 K. Some weaker features at equatorial latitudes were also recovered but these could be partially spurious and appear blurred due to imperfect phase coverage. We use our line profiles to reconstruct an average non-sphericity of R pole /R point = 0.96 which would, if not taken into account, mimic a temperature difference pole-to-equator of ≈220 K, especially at the phases of quadrature. Finally, we apply two different methods for restoring surface differential rotation and found a weak solar-type rotation law with a shear ∆Ω ≈ 0.95• /day (α = ∆Ω/Ω eq = +0.049 ± 0.003), i.e. roughly a factor of four weaker at a rotation rate roughly 1.5 times faster than the Sun's.

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“…An integration time of 600 s per exposure gave a peak S /N of 300:1 per resolution element. For a brief description of the data reduction, we refer to the paper by Strassmeier & Rice (2003). The data log summary is given in Table 1.…”

Section: Cfht/gecko Spectroscopy In 2000mentioning

confidence: 99%

Binary-induced magnetic activity?

Strassmeier

Carroll

Weber

et al. 2011

A&A

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Context. Multi-wavelength time-series observations with high cadence and long duration are needed to resolve and understand the many variations of magnetically active late-type stars, which is an approach often used to observe the Sun. Aims. We present a first and detailed study of the bright and active K0IV-III star HD 123351. Methods. We acquired a total of 955 high-resolution STELLA echelle spectra during the years 2006-2010 and a total of 2260 photometric VI C data points during 1998-2010. These data are complemented by some spectra from CFHT and KPNO. Results. The star is found to be a single-lined spectroscopic binary with a period of 147.8919 ± 0.0003 days and a large eccentricity of e = 0.8086 ± 0.0001. The rms of the orbital solution is just 47 m s −1 , making it the most precise orbit ever obtained for an active binary system. The rotation period is constrained from long-term photometry to be 58.32 ± 0.01 days. It shows that HD 123351 is a very asynchronous rotator, rotating five times slower than the expected pseudo-synchronous value. Two spotted regions persisted throughout the 12 years of our observations. We interpret them as active longitudes on a differentially rotating surface with a ΔP/P of 0.076. Four years of Hα, Ca ii H&K and He i D3 monitoring identifies the same main periodicity as the photometry but dynamic spectra also indicate that there is an intermittent dependence on the orbital period, in particular for Ca ii H&K in 2008. Line-profile inversions of a pair of Zeeman sensitive/insensitive iron lines yield an average surface magnetic-flux density of 542 ± 72 G. The time series for 2008 is modulated by the stellar rotation as well as the orbital motion, such that the magnetic flux is generally weaker during times of periastron and that the chromospheric emissions vary in anti-phase with the magnetic flux. We also identify a broad and asymmetric lithium line profile and measure an abundance of log n(Li) = 1.70 ± 0.05. The star's position in the H-R diagram indicates a mass of 1.2 ± 0.1 M and an age of 6-7 Gyr. Conclusions. We interpret the anti-phase relation of the magnetic flux with the chromospheric emissions as evidence that there are two magnetic fields present at the same time, a localized surface magnetic field associated with spots and a global field that is oriented towards the (low-mass) secondary component. We suggest that the inter-binary field is responsible for the magnetic-flux dilution at periastron. It is also likely to be responsible for the unexpected slow and asynchronous rotation of the primary star.

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Doppler imaging of stellar surface structure

Cited by 46 publications

References 36 publications

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

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

Doppler imaging of stellar surface structure

Binary-induced magnetic activity?

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