Doppler imaging of stellar surface structure

Strassmeier, K. G.; Pichler, Thomas; Weber, M.; Granzer, T.

doi:10.1051/0004-6361:20031538

Cited by 38 publications

(75 citation statements)

References 48 publications

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“…where the rotational period (P rot ) is nearly identical to the value of 1.3371 days found by Strassmeier et al (2003). With a periodogram analysis and a clean deconvolution algorithm (Roberts et al 1987) we found a period of 1.37 ± 0.12 days that is fully consistent with the value of Järvinen et al (2008), taking the limited time span of our data into account.…”

Section: Light Curve and Spot Modelingsupporting

confidence: 85%

“…With only two photometric bands and the rather small amplitude of the light curve it is not easy to derive the spot temperature. Thus we preferred to fix the spot temperature, ΔT = 1500 K, close to the values found for high latitude spots by Strassmeier et al (2003) and Järvinen et al (2008) with DI technique, and let the spot area and location be free to vary. In order to minimize the degrees of freedom and still allowing the code to reproduce an asymmetric light curve, only two spots have been put on the photosphere.…”

Section: Light Curve and Spot Modelingmentioning

confidence: 99%

“…It is probably the brightest single early-G type star that is rotating fast enough for mapping its photosphere through Doppler imaging (DI). Strassmeier et al (2003) made the first dedicated photometric and spectroscopic study of HD 171488 in which they defined its astrophysical parameters, concluding that it is a single G0V main-sequence star with an age of about 30-50 Myr based on both its position on the HR diagram and the lithium content. They also made the first reconstruction of its photosphere through the DI technique, showing a big polar spot with additional high-latitude features.…”

Section: Introductionmentioning

confidence: 99%

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Photospheric and chromospheric activity on the young solar-type star HD 171488 (V889 Herculis)

Frasca¹,

Biazzo

Kővári³

et al. 2010

A&A

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Aims. We present the results of contemporaneous spectroscopic and photometric monitoring of the young solar-type star HD 171488 (P rot 1.337 days) aimed at studying surface inhomogeneities at both photospheric and chromospheric levels. Methods. Echelle FOCES spectra (R 40 000) and Johnson BV photometry have been performed in August 2006, with a good coverage of rotational phases. Spectral type, rotational velocity, metalicity, and gravity were determined with a code developed by us (Rotfit) and a library of high-resolution spectra of slowly-rotating reference stars. The metalicity was measured from the analysis of iron lines with the Moog code. The spectral subtraction technique was applied to the most relevant chromospheric diagnostics included in the FOCES spectral range, namely Ca ii IRT, Hα, He i D 3 , Hβ, and Ca ii H&K lines.Results. A simple model with two large high-latitude spots is sufficient to reproduce the B and V light curves as well as the radial velocity modulation if a temperature difference between photosphere and spots of about 1500 K is used. A Doppler-imaging analysis of photospheric lines basically confirms a similar spot distribution. With the help of an analogous geometric two-spot model, we are able to reproduce the observed modulations in the residual chromospheric emissions adopting different values of ratios between the flux of plages and the quiet chromosphere (about 5 for Hα and 3 for Ca ii diagnostics). Facular regions of solar type appear to be the main responsible features for the modulations of chromospheric diagnostics. Both the spot/plage model and the cross-correlation between the light curve and the chromospheric line fluxes display a significant lead effect of plages with respect to spots (from 20 • to 40 • in longitude), as already observed in some active solar-type stars and RS CVn systems. Conclusions. The contemporaneous monitoring of photospheric and chromospheric diagnostics in the young and rapidly rotating solar-type star HD 171488 allowed us to detect active regions which have nearly the same location at both atmospheric layers, with plages slightly leading spots in longitudes. These active regions are similar to the solar ones in some respects, because the spot temperature is close to that of sunspot umbrae and the plage flux-contrast is consistent with the average solar values. The main differences with respect to the Sun are larger sizes and higher latitudes.

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Section: Light Curve and Spot Modelingsupporting

confidence: 85%

Section: Light Curve and Spot Modelingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photospheric and chromospheric activity on the young solar-type star HD 171488 (V889 Herculis)

Frasca¹,

Biazzo

Kővári³

et al. 2010

A&A

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“…HD 171488 (V889 Her) is a young active G dwarf. Strassmeier et al (2003) found a photospheric temperature of 5830 K, a rotation period of 1.337 days, a mass of 1.06 ± 0.05 solar masses, a radius of 1.09 ± 0.05 solar radii, and an age of 30−50 Myr. Marsden et al (2006) find a rotation period of 1.313 days, a photospheric temperature of 5800 K, and a radius of 1.15 ± 0.08 solar radii.…”

Section: R58 Lq Lup and Hd 171488mentioning

confidence: 97%

The differential rotation of G dwarfs

Küker

Rüdiger

Kitchatinov

2011

A&A

108

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A series of stellar models of spectral type G is computed to study the rotation laws resulting from mean-field equations. The rotation laws of the slowly rotating Sun, the rapidly rotating MOST stars Eri and κ 1 Cet, and the rapid rotators R58 and LQ Lup can be easily reproduced. We also find that differences in the depth of the convection zone cause large differences in the surface rotation law and that the extreme surface shear of HD 171488 can only be explained with an artificially shallow convection layer. We verify the thermal wind equilibrium in rapidly rotating G dwarfs and find that the polar subrotation (dΩ/dz < 0) is due to the baroclinic effect and the equatorial superrotation (dΩ/dr > 0) is caused by the Reynolds stresses. In the bulk of the convection zones where the meridional flow is slow and smooth, the thermal wind equilibrium holds between the centrifugal and the pressure forces. It does not hold, however, in the bounding shear layers including the equatorial region where the Reynolds stresses dominate.

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“…Active longitudes show a high spot coverage stretching over a large area of the star, persisting for many months or years, which translates into several hundreds of stellar rotations. It is largely unknown whether their internal structure is variable, i.e., to what degree spots move, disappear, or form inside of Article published by EDP Sciences Strassmeier et al (2003).…”

Section: Introductionmentioning

confidence: 99%

Long-term stability of spotted regions and the activity-induced Rossiter-McLaughlin effect on V889 Herculis

Huber¹,

Wolter²,

Czesla³

et al. 2009

A&A

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Context. The young active G-dwarf star V889 Herculis (HD 171488) shows pronounced spots in Doppler images as well as large variations in photometry and radial velocity (RV) measurements. However, the lifetime and evolution of its active regions are not well known. Aims. We study the existence and stability of active regions on the star's surface using complementary data and methods. Furthermore, we analyze the correlation of spot-induced RV variations and Doppler images. Methods. Photometry and high-resolution spectroscopy are used to examine stellar activity. A CLEAN-like Doppler imaging (DI) algorithm is used to derive surface reconstructions. We study high-precision RV curves to determine their modulation due to stellar activity in analogy to the Rossiter-McLaughlin effect. To this end we develop a measure for the shift of a line's center and compare it to RV measurements. Results. We show that large spotted regions are present on V889 Her for more than one year, remaining similar in their large scale structure and position. This applies to several time periods of our observations, which cover more than a decade. We use DI line profile reconstructions to identify the influence of long-lasting starspots on RV measurements. In this way we verify the RV curve's agreement with our Doppler images. Based on long-term RV data we confirm V889 Her's rotation period of 1.3371 ± 0.0002 days.

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Doppler imaging of stellar surface structure

Cited by 38 publications

References 48 publications

Photospheric and chromospheric activity on the young solar-type star HD 171488 (V889 Herculis)

Photospheric and chromospheric activity on the young solar-type star HD 171488 (V889 Herculis)

The differential rotation of G dwarfs

Long-term stability of spotted regions and the activity-induced Rossiter-McLaughlin effect on V889 Herculis

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