Oscillation mode linewidths of main-sequence and subgiant stars observed by<i>Kepler</i>

Appourchaux, T.; Benomar, O.; Gruberbauer, M.; Chaplin, W. J.; García, Rafael A.; Handberg, R.; Verner, G. A.; Antia, H. M.; Campante, Tiago L.; Davies, G. R.; Deheuvels, S.; Hekker, S.; Howe, R.; Salabert, D.; Bedding, Timothy R.; White, T. R.; Houdek, G.; Aguirre, V. Silva; Elsworth, Y.; Cleve, J. Van; Clarke, Bruce; Hall, Jennifer R.; Kjeldsen, H.

doi:10.1051/0004-6361/201118496

Cited by 77 publications

(141 citation statements)

References 32 publications

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“…Using CoRoT data, Baudin et al (2011) have found that τ max scales approximately as T −m eff where m = 16.2 ± 2 for the main-sequence and sub-giant stars. Recently, Appourchaux et al (2012) have found a slope m = 15.5 ± 1.6 with Kepler data, which is hence compatible with that of Baudin et al (2011). Such a power law is also supported by the theoretical calculations of Belkacem et al (2012) performed for main-sequence, sub-and red giant stars.…”

Section: Theoretical Scaling Relation For the Velocity Mode Amplitudesupporting

confidence: 74%

Amplitudes of solar-like oscillations in red giant stars

Samadi

Belkacem

Dupret

et al. 2012

A&A

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Context. A growing number of solar-like oscillations has been detected in red giant stars thanks to the CoRoT and Kepler space-crafts. In the same way as for main-sequence stars, mode driving is attributed to turbulent convection in the uppermost convective layers of those stars. Aims. The seismic data gathered by CoRoT on red giant stars allow us to test the mode driving theory in physical conditions different from main-sequence stars. Methods. Using a set of 3D hydrodynamical models representative of the upper layers of sub-and red giant stars, we computed the acoustic mode energy supply rate (P max ). Assuming adiabatic pulsations and using global stellar models that assume that the surface stratification comes from the 3D hydrodynamical models, we computed the mode amplitude in terms of surface velocity. This was converted into intensity fluctuations using either a simplified adiabatic scaling relation or a non-adiabatic one. Results. From L and M (the luminosity and mass), the energy supply rate P max is found to scale as (L/M) 2.6 for both main-sequence and red giant stars, extending previous results. The theoretical amplitudes in velocity under-estimate the Doppler velocity measurements obtained so far from the ground for red giant stars by about 30%. In terms of intensity, the theoretical scaling law based on the adiabatic intensity-velocity scaling relation results in an under-estimation by a factor of about 2.5 with respect to the CoRoT seismic measurements. On the other hand, using the non-adiabatic intensity-velocity relation significantly reduces the discrepancy with the CoRoT data. The theoretical amplitudes remain 40% below, however, the CoRoT measurements. Conclusions. Our results show that scaling relations of mode amplitudes cannot be simply extended from main-sequence to red giant stars in terms of intensity on the basis of adiabatic relations because non-adiabatic effects for red giant stars are important and cannot be neglected. We discuss possible reasons for the remaining differences.

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Section: Theoretical Scaling Relation For the Velocity Mode Amplitudesupporting

confidence: 74%

Amplitudes of solar-like oscillations in red giant stars

Samadi

Belkacem

Dupret

et al. 2012

A&A

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“…Previous observations did not report a similar T eff dependence [4]. On the contrary, this kind of T eff dependence was firmly established for main-sequence and subgiant stars [1,4]. However, we find a power law with a small exponent, whereas a high value is observed for the other solar-like pulsators, so that our results are far from the ones observed for main-sequence stars.…”

Section: The γ 0 -T Eff Relationcontrasting

confidence: 99%

“…Individual mode widths (Γ 0 ) were computed following [1] for each of the stars. A mean value of Γ 0 is derived from the weighted average of the width of the three radial modes closest to ν max .…”

Section: Measurement Of the Star Radial Mode Linewidthsmentioning

confidence: 99%

Radial mode widths in red giant stars spectra observed byKepler

2017

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Abstract. The Kepler space mission has observed many solar-like pulsators, and helped to decipher their fundamental parameters (e.g: mass, radius, rotation). Most of the achievements recently obtained in that domain result from the analysis of the mode frequencies. However, unique information on non-adiabatic physics derives from the height and width of the modes. In this study, we aim at measuring the mode widths of the pressure modes in thousands of Kepler red giants and to analyze their variations in function of stellar parameters. To achieve that, we used a peakbagging technique on the star radial modes. The results show a relation between the radial mode linewidth and the effective temperature of the star as theoretically predicted. We also unveil a clear dependence with mass and stellar evolution for the radial mode width. This means that the mode damping depends on the evolutionary status of the stars.

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“…(1) in Appourchaux et al (2014) and Eq. (2) in Appourchaux et al (2012). Next, the background power spectral density, B(ν), across the frequency range occupied by the modes is dominated by contributions from granulation and shot noise.…”

Section: Pulsation Frequenciesmentioning

confidence: 99%

SpaceInn hare-and-hounds exercise: Estimation of stellar properties using space-based asteroseismic data

Reese

Chaplin

Davies

et al. 2016

A&A

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Context. Detailed oscillation spectra comprising individual frequencies for numerous solar-type stars and red giants are either currently available, e.g. courtesy of the CoRoT, Kepler, and K2 missions, or will become available with the upcoming NASA TESS and ESA PLATO 2.0 missions. The data can lead to a precise characterisation of these stars thereby improving our understanding of stellar evolution, exoplanetary systems, and the history of our galaxy. Aims. Our goal is to test and compare different methods for obtaining stellar properties from oscillation frequencies and spectroscopic constraints. Specifically, we would like to evaluate the accuracy of the results and reliability of the associated error bars, and to see where there is room for improvement. Methods. In the context of the SpaceInn network, we carried out a hare-and-hounds exercise in which one group, the hares, simulated observations of oscillation spectra for a set of ten artificial solar-type stars, and a number of hounds applied various methods for characterising these stars based on the data produced by the hares. Most of the hounds fell into two main groups. The first group used forward modelling (i.e. applied various search/optimisation algorithms in a stellar parameter space) whereas the second group relied on acoustic glitch signatures. Results. Results based on the forward modelling approach were accurate to 1.5% (radius), 3.9% (mass), 23% (age), 1.5% (surface gravity), and 1.8% (mean density), as based on the root mean square difference. Individual hounds reached different degrees of accuracy, some of which were substantially better than the above average values. For the two 1 M stellar targets, the accuracy on the age is better than 10% thereby satisfying the requirements for the PLATO 2.0 mission. High stellar masses and atomic diffusion (which in our models does not include the effects of radiative accelerations) proved to be sources of difficulty. The average accuracies for the acoustic radii of the base of the convection zone, the He II ionisation, and the Γ 1 peak located between the two He ionisation zones were 17%, 2.4%, and 1.9%, respectively. The results from the forward modelling were on average more accurate than those from the glitch fitting analysis as the latter seemed to be affected by aliasing problems for some of the targets. Conclusions. Our study indicates that forward modelling is the most accurate way of interpreting the pulsation spectra of solar-type stars. However, given its model-dependent nature, this method needs to be complemented by model-independent results from, e.g. glitch analysis. Furthermore, our results indicate that global rather than local optimisation algorithms should be used in order to obtain robust error bars.

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Oscillation mode linewidths of main-sequence and subgiant stars observed byKepler

Cited by 77 publications

References 32 publications

Amplitudes of solar-like oscillations in red giant stars

Amplitudes of solar-like oscillations in red giant stars

Radial mode widths in red giant stars spectra observed byKepler

SpaceInn hare-and-hounds exercise: Estimation of stellar properties using space-based asteroseismic data

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