On deriving <i>p</i>-mode parameters for inclined solar-like stars

Ballot, J.; Appourchaux, T.; Toutain, T.; Guittet, Mélanie

doi:10.1051/0004-6361:20079343

Cited by 63 publications

(65 citation statements)

References 16 publications

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“…These values -which are slightly higher than solarare consistent with the value given in Michel et al (2008), which was derived from a different method of analysis. It is important to recognise that, even when heights and widths have large errors or are biased, the power of modes -and hence their amplitudesare generally correctly estimated and with a smaller fractional error than the two parameters separately; it has been shown, for instance, that poor estimation of the inclination could simultaneously bias the fitted heights and widths, but not the power (Ballot et al 2008). In this sense, the derived values of the amplitudes are robust.…”

Section: Resultsmentioning

confidence: 96%

“…The splitting parameter is difficult to estimate because when modes have large line widths, blending of the components of multiplets, and even of adjacent = 2 and l = 0 modes, results. This blending creates a strong correlation of the splitting parameter with the inclination parameter, making it difficult to disentangle the two (Ballot et al 2006(Ballot et al , 2008. A global fitting, as performed in this paper, can help to alleviate some of these problems.…”

Section: Resultsmentioning

confidence: 99%

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Solar-like oscillations in HD 181420: data analysis of 156 days of CoRoT data

Barban¹,

Deheuvels²,

Baudin

et al. 2009

A&A

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127

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Context. The estimate of solar-like oscillation properties, such as their frequencies, amplitudes and lifetimes, is challenging because of their low amplitudes and will benefit from long and uninterrupted observing runs. The space telescope CoRoT allows us to obtain high-performance photometric data over a long and quasi continuous period. Among its main targets are stars for which we expect solar-like oscillations. Aims. HD 181420, an F2 main sequence star, has been observed by CoRoT during its first long run covering about 156 days. With this unprecedently high-quality set of data, our aim is to derive the p-mode parameters that can be used to probe the stellar interior. Methods. The CoRoT data obtained on HD 181420 is analysed using a classical Fourier approach for the search for the p mode signature. The p-mode parameters are then derived using global fitting of the power spectrum by a Lorentzian model, as used widely in the solar case. Results. From the p-mode frequencies, the mean value of the large spacing is estimated to be 75 μHz. The p-mode amplitudes are slightly less than 4 ppm with a line width of about 8 μHz at the maximum of the p modes. The inclination angle is estimated to be around 45 • . The large mode line-width combined with the observed mode spacing make it difficult to identify the = 2 modes and to estimate the rotational splitting. We explore two scenarios for the identification of the modes.

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Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

Solar-like oscillations in HD 181420: data analysis of 156 days of CoRoT data

Barban¹,

Deheuvels²,

Baudin

et al. 2009

A&A

Self Cite

127

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show abstract

“…From the spot modeling (Mosser et al 2009a) a value of 45 ± 10 • was found. This parameter is extremely important because it affects the amplitude ratios of the components of a multiplet of non-radial modes, and it is strongly connected to the rotational splitting (see, for example, Ballot et al 2008, and references therein).…”

Section: Constraining the Inclination Anglementioning

confidence: 99%

“…It is not only the lower signal-to-noise ratio of the p-mode asteroseismic signal that makes the fitting difficult, but also the high correlation between the inclination and the rotational splitting (Ballot et al 2006(Ballot et al , 2008. Because of that, the determination of these two parameters can be rather poor and will consequently affect the determination of the other parameters (frequencies, widths, heights, etc.).…”

Section: Extracting Individual P-mode Characteristicsmentioning

confidence: 99%

Solar-like oscillations with low amplitude in the CoRoT target HD 181906

García

Régulo

Samadi

et al. 2009

A&A

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104

113

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Context. The F8 star HD 181906 (effective temperature ∼6300 K) was observed for 156 days by the CoRoT satellite during the first long run in the direction of the galactic centre. Analysis of the data reveals a spectrum of solar-like acoustic oscillations. However, the faintness of the target (m v = 7.65) means the signal-to-noise (S/N) in the acoustic modes is quite low, and this low S/N leads to complications in the analysis. Aims. We extract global variables of the star, as well as key parameters of the p modes observed in the power spectrum of the lightcurve. Methods. The power spectrum of the lightcurve, a wavelet transform and spot fitting were used to obtain the average rotation rate of the star and its inclination angle. Then, the autocorrelation of the power spectrum and the power spectrum of the power spectrum were used to properly determine the large separation. Finally, estimations of the mode parameters were done by maximizing the likelihood of a global fit, where several modes were fit simultaneously. Results. We have been able to infer the mean surface rotation rate of the star (∼4 μHz) with indications of the presence of surface differential rotation, the large separation of the p modes (∼87 μHz), hence also the "ridges" corresponding to overtones of the acoustic modes.

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“…Moreover, combined with the measured v sin i = 19.0 ± 1.5 km s −1 (see Sect. 2) and assuming a given radius of the star, we can also estimate the inclination axis of the star, which can be very helpful to better constrain the fitting techniques to characterise the acoustic modes (Gizon & Solanki 2003;Ballot et al 2006Ballot et al , 2008.…”

Section: Surface Rotationmentioning

confidence: 99%

The solar-like CoRoT target HD 170987: spectroscopic and seismic observations

Mathur

García²,

Catala

et al. 2010

A&A

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Context. The CoRoT mission is in its third year of observation and the data from the second long run in the galactic centre direction are being analysed. The solar-like oscillating stars that have been observed up to now have given some interesting results, specially concerning the amplitudes that are lower than predicted. We present here the results from the analysis of the star HD 170987. Aims. The goal of this research work is to characterise the global parameters of HD 170987. We look for global seismic parameters such as the mean large separation, maximum amplitude of the modes, and surface rotation because the signal-to-noise ratio in the observations does not allow us to measure individual modes. We also aim to retrieve the parameters of the star and its chemical composition.Methods. We studied the chemical composition of the star through ground-based observations performed with the NARVAL spectrograph. We used several methods to calculate the global parameters from the acoustic oscillations based on CoRoT data. The light curve of the star has been interpolated with inpainting algorithms to reduce the effect of data gaps. Results. We found the power excess related to p modes in the range [400-1200] μHz with a mean large separation of 55.2 ± 0.8 μHz with a probability above 95 % that increases to 55.9 ± 0.2 μHz in a higher frequency range μHz and a rejection level of 1%. A hint of the variation of this quantity with frequency was also found. The rotation period of the star is estimated to be around 4.3 days with an inclination axis of i = 50 • +20 −13 . We measured a bolometric amplitude per radial mode in a range [2.4-2.9] ppm around 1000 μHz. Finally we estimate the stellar mass with a grid of models, M = 1.43 ± 0.05 M , the radius, R = 1.96 ± 0.046 R , and the age ∼2.4 Gyr.

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On deriving p-mode parameters for inclined solar-like stars

Cited by 63 publications

References 16 publications

Solar-like oscillations in HD 181420: data analysis of 156 days of CoRoT data

Solar-like oscillations in HD 181420: data analysis of 156 days of CoRoT data

Solar-like oscillations with low amplitude in the CoRoT target HD 181906

The solar-like CoRoT target HD 170987: spectroscopic and seismic observations

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