Inferred acoustic rates of solar<i>p</i> modes from several helioseismic instruments

Baudin, F.; Samadi, R.; Goupil, M. J.; Appourchaux, T.; Barban, C.; Boumier, P.; Chaplin, W. J.; Gouttebroze, P.

doi:10.1051/0004-6361:20041229

Cited by 59 publications

(102 citation statements)

References 25 publications

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“…Relative heights inside a given multiplet, r ,m , are computed following Gizon & Solanki (2003) and depend on the inclination only. We recall here that the relation between the height of the Lorentzian profile, H n,0 , in the power density spectrum and the mode amplitude in ppm, a n , is given by: a 2 n = πH n,0 Γ n (see for example Baudin et al 2005, for more details). -ν n, : the mode frequency for each degree and for m = 0.…”

Section: Methodsmentioning

confidence: 99%

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: Methodsmentioning

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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“…On the other hand, low-frequency mode masses are much less sensitive to the choice of r h . Accordingly, the discrepancy seen at low frequency between GOLF and the other data sets suggests that the absolute calibration of the GOLF data may not be correct (see Baudin et al 2005). In Fig.…”

Section: Seismic Constraintsmentioning

confidence: 99%

“…The optical depth associated with the different spectral lines used in helioseismology are given in Houdek (2006) with associated references. Solar p-mode excitation rates, P, derived by Baudin et al (2005) are shown in Fig. 1 (left panel).…”

Section: Seismic Constraintsmentioning

confidence: 99%

Stochastic Excitation of Acoustic Modes in Stars

Samadi

2011

The Pulsations of the Sun and the Stars

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Abstract. For more than ten years, solar-like oscillations have been detected and frequencies measured for a growing number of stars with various characteristics (e.g. different evolutionary stages, effective temperatures, gravities, metal abundances ...).Excitation of such oscillations is attributed to turbulent convection and takes place in the uppermost part of the convective envelope. Since the pioneering work of Goldreich & Keely (1977), more sophisticated theoretical models of stochastic excitation were developed, which differ from each other both by the way turbulent convection is modelled and by the assumed sources of excitation. We review here these different models and their underlying approximations and assumptions.We emphasize how the computed mode excitation rates crucially depend on the way turbulent convection is described but also on the stratification and the metal abundance of the upper layers of the star. In turn we will show how the seismic measurements collected so far allow us to infer properties of turbulent convection in stars.

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“…We compute the mean-squared surface velocity for each mode according to the relation (Baudin et al 2005):…”

Section: Surface Velocitiesmentioning

confidence: 99%

“…Equation (65) involves the damping rates (η = πΓ ν ) inferred from observational data in the solar case for low-modes (see Baudin et al 2005, for details). We then assume that the damping rates are roughly the same as for the = 0 modes.…”

Section: Surface Velocitiesmentioning

confidence: 99%

Stochastic excitation of non-radial modes

Belkacem¹,

Samadi²,

Goupil³

et al. 2007

A&A

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Context. Turbulent motions in stellar convection zones generate acoustic energy, part of which is then supplied to normal modes of the star. Their amplitudes result from a balance between the efficiencies of excitation and damping processes in the convection zones. Aims. We develop a formalism that provides the excitation rates of non-radial global modes excited by turbulent convection. As a first application, we estimated the impact of non-radial effects on excitation rates and amplitudes of the high-angular-degree modes that are observed on the Sun. Methods. A model of stochastic excitation by turbulent convection was developed to compute the excitation rates and then successfully applied to solar radial modes. We generalise this approach to the case of non-radial global modes. This enables us to estimate the energy supplied to high-( ) acoustic modes. Qualitative arguments, as well as numerical calculations, are used to illustrate the results. Results. We find that non-radial effects for p modes are non-negligible: -For high-n modes (i.e. typically n > 3) and for high values of , the power supplied to the oscillations depends on the mode inertia. -For low-n modes, independent of the value of , the excitation is dominated by the non-radial components of the Reynolds stress term. Conclusions. Our numerical investigation of high-p modes shows that the validity of the present formalism is limited to < 500 due to the spatial separation of scale assumption. Thus, a model for very high-p-mode excitation rates calls for further theoretical developments; however, the formalism is valid for solar g modes, which will be investigated in a paper in preparation.

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Inferred acoustic rates of solarp modes from several helioseismic instruments

Cited by 59 publications

References 25 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

Stochastic Excitation of Acoustic Modes in Stars

Stochastic excitation of non-radial modes

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