Measuring Stellar Differential rotation with asteroseismology

Gizon, Laurent; Solanki, S. K.

doi:10.1023/b:sola.0000031378.29215.0c

Cited by 55 publications

(48 citation statements)

References 17 publications

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“…We also find evidence of differential rotation, and show that independent measurements of the star inclination will be of great help in inferring the rate of differential rotation. Spot modeling may then achieve complementary results to asteroseismology (Gizon & Solanki 2004;Ballot et al 2006). A dedicated analysis of differential rotation will be presented in a forthcoming work.…”

Section: Resultsmentioning

confidence: 99%

Short-lived spots in solar-like stars as observed by CoRoT

Mosser¹,

Baudin

Lanza

et al. 2009

A&A

117

119

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Context. CoRoT light curves have an unprecedented photometric quality, having simultaneously a high signal-to-noise ratio, a long time span and a nearly continuous duty-cycle. Aims. We analyse the light-curves of four bright targets observed in the seismology field and study short-lived small spots in solar-like stars.Methods. We present a simple spot modeling by iterative analysis. Its ability to extract relevant parameters is ensured by implementing relaxation steps to avoid convergence to local minima of the sum of the residuals between observations and modeling. The use of Monte-Carlo simulations allows us to estimate the performance of the fits. Results. Our starspot modeling gives a representation of the spots on these stars in agreement with other well tested methods. Within this framework, parameters such as rigid-body rotation and spot lifetimes seem to be precisely determined. Then, the lifetime/rotation period ratios are in the range 0.5−2, and there is clear evidence for differential rotation.

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Section: Resultsmentioning

confidence: 99%

Short-lived spots in solar-like stars as observed by CoRoT

Mosser¹,

Baudin

Lanza

et al. 2009

A&A

117

119

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show abstract

“…Recently, this method was used for single Kepler light curves (Frasca et al 2011;Fröhlich et al 2012) where DR is the favorite explanation for the light curve shape. Asteroseismology provides another approach, explaining frequency splitting of global oscillations in terms of different latitudinal rotation rates (Gizon & Solanki 2004).…”

Section: Introductionmentioning

confidence: 99%

Rotation and differential rotation of activeKeplerstars

Reinhold

Reiners

Basri

2013

A&A

350

397

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Context. The Kepler space telescope monitors more than 160 000 stars with an unprecedented precision providing the opportunity to study the rotation of thousands of stars. Aims. We present rotation periods for thousands of active stars in the Kepler field derived from Q3 data. In most cases a second period close to the rotation period was detected that we interpreted as surface differential rotation (DR). We show how the absolute and relative shear (ΔΩ and α = ΔΩ/Ω, respectively) correlate with rotation period and effective temperature. Methods. Active stars were selected from the whole sample using the range of the variability amplitude. To detect different periods in the light curves we used the Lomb-Scargle periodogram in a pre-whitening approach to achieve parameters for a global sine fit. The most dominant periods from the fit were associated to different surface rotation periods. Our purely mathematical approach is capable of detecting different periods but cannot distinguish between the physical origins of periodicity. We ascribe the existence of different periods to DR, but spot evolution could also play a role. Because of the large number of stars the period errors are estimated statistically. We thus cannot exclude the existence of false positives among our periods.Results. In our sample of 40 661 active stars we found 24 124 rotation periods P 1 between 0.5 and 45 days, with a mean of P 1 = 16.3 days. The distribution of stars with 0.5 < B − V < 1.0 and ages derived from angular momentum evolution that are younger than 300 Myr is consistent with a constant star-formation rate; the detection among older stars is incomplete probably because of our active sample selection. A second period P 2 within ±30% of the rotation period P 1 was found in 18 616 stars (77.2%). Attributing these two periods to DR we found that for active stars other than the Sun the relative shear α increases with rotation period, and slightly decreases with effective temperature. The absolute shear ΔΩ slightly increases from ΔΩ = 0.079 rad d −1 at T eff = 3500 K to ΔΩ = 0.096 rad d −1 at T eff = 6000 K. Above 6000 K, ΔΩ shows much larger scatter. The dependence of ΔΩ on rotation period is weak over a large period range. Conclusions. Latitudinal differential rotation measured for the first time in more than 18 000 stars provides a comprehensive picture of stellar surface shear. This picture is consistent with major predictions from mean-field theory, and seems to support these models. To what extent our observations are prone to false positives and selection bias has not been fully explored, and needs to be addressed using other data, including the full Kepler time coverage.

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“…for white dwarfs (Kawaler et al 1999), solar-type stars (Gizon & Solanki 2004), and B stars (Suárez et al 2007) using rotationally split frequencies of stellar oscillations. A&A 542, A116 (2012) Stellar differential rotation cannot be observed directly since the surface of stars can usually not be imaged with sufficient resolution.…”

Section: Introductionmentioning

confidence: 99%

New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?

Eiff

Reiners

2012

A&A

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Context. The Sun displays differential rotation that is intimately connected to the solar dynamo and hence related to solar activity, the solar cycle, and the solar wind. Considering the detectability and habitability of planets around other stars it is important to understand the role of differential rotation in other stars. Aims. We present projected rotational velocities and new measurements of the rotational profile of some 180 nearby stars with spectral types A-F. The results are consolidated by a homogeneous compilation of basic stellar data from photometry and the identification of multiple stellar systems. New and previous measurements of rotation by line profile analysis are compiled and made available. Methods. The overall broadening profile is derived analysing spectral line shape from hundreds of spectral lines by the method of least-squares deconvolution, reducing spectral noise to a minimum. The effect of differential rotation on the broadening profile is best measured in inverse wavelength space by the first two zeros of its Fourier transform. Results. Projected rotational velocity v sin i is measured for more than 110 of the sample stars. Rigid and differential rotation can be distinguished in 56 cases where v sin i > 12 km s −1 . We detect differential rotation rates of δΩ Ω = 5% and more. Ten stars with significant differential rotation rates are identified. The line shapes of 46 stars are consistent with rigid rotation, even though differential rotation at very low rates might still be possible in these cases. The strongest amount of relative differential rotation (54%) detected by line profile analysis is found among F stars. Conclusions. As of now, 33 differential rotators detected by line profile analysis have been confirmed. The frequency of differential rotators decreases towards high effective temperature and rapid rotation. There is evidence for two populations of differential rotators, one of rapidly rotating A stars at the granulation boundary with strong horizontal shear and one of mid-to late-F type stars with moderate rates of rotation and less shear. The gap in between can only partly be explained by an upper bound found for the horizontal shear of F stars. Apparently, the physical conditions change at early-F spectral types. The range of horizontal shear observed for mid-type F stars is reproduced by theoretical calculations while there seems to be a discrepancy in period dependence for late-F stars.

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Measuring Stellar Differential rotation with asteroseismology

Cited by 55 publications

References 17 publications

Short-lived spots in solar-like stars as observed by CoRoT

Short-lived spots in solar-like stars as observed by CoRoT

Rotation and differential rotation of activeKeplerstars

New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?

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