Oscillating red giants in the CoRoT exofield: asteroseismic mass and radius determination

Kallinger, T.; Weiß, W. W.; Barban, C.; Baudin, F.; Cameron, Chris; Carrier, F.; Ridder, J. De; Goupil, M. J.; Gruberbauer, M.; Hatzes, A. P.; Hekker, S.; Samadi, R.; Deleuil, M.

doi:10.1051/0004-6361/200811437

Cited by 183 publications

(207 citation statements)

References 40 publications

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“…(3)). Concerning Δν, as first established by Stello et al (2009), Hekker et al (2009 and Kallinger et al (2010), there is a clear scaling relation between this quantity and ν max . We derived this quantity here according to the relation derived by Mosser et al (2010) from a large set of CoRoT red giant stars:…”

Section: Maximum Velocity Amplitude (V Max )mentioning

confidence: 61%

“…Thanks to CoRoT and Kepler, it is now possible to detect and measure solar-like oscillations in many more (several thousands) red giant stars (e.g., de Ridder et al 2009;Huber et al 2010;Bedding et al 2010;Kallinger et al 2010;Stello et al 2011;Mosser et al 2012). With such a large set of stars, it is possible to perform ensemble asteroseismology by deriving scaling relations that relate seismic parameters to a few fundamental stellar parameters (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…masses, radii, luminosities etc.). These approaches are now commonly applied to global seismic parameters, such as the cutoff-frequency or peak frequency (e.g., Miglio et al 2009;Stello et al 2009;Kallinger et al 2010;Mosser et al 2010). However, scaling relation is used only infrequently for mode amplitudes.…”

Section: Introductionmentioning

confidence: 99%

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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: Maximum Velocity Amplitude (V Max )mentioning

confidence: 61%

Section: Introductionmentioning

confidence: 99%

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Amplitudes of solar-like oscillations in red giant stars

Samadi

Belkacem

Dupret

et al. 2012

A&A

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“…To check this, we fit a Gaussian to the simulated power excess and find the power to be symmetrically distributed around ν max,ref = 49.61±0.06 μHz. We note that in reality the shape of the pulsation power excess is not necessarily Gaussian but as long as the power is distributed roughly symmetric (and there is no indication that it is not, see, e.g., Kallinger et al 2010c) any symmetric function will give a good estimate of the intrinsic centre of the power excess.…”

Section: Systematic Effects On ν Maxmentioning

confidence: 88%

The connection between stellar granulation and oscillation as seen by theKeplermission

Kallinger

Ridder

Hekker

et al. 2014

A&A

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Context. The long and almost continuous observations by Kepler show clear evidence of a granulation background signal in a large sample of stars, which is interpreted as the surface manifestation of convection. It has been shown that its characteristic timescale and rms intensity fluctuation scale with the peak frequency (ν max ) of the solar-like oscillations. Various attempts have been made to quantify the observed signal, to determine scaling relations for its characteristic parameters, and to compare them to theoretical predictions. Even though they are consistent on a global scale, large systematic differences of an unknown origin remain between different methods, as well as between the observations and simulations. Aims. We aim to study different approaches to quantifying the signature of stellar granulation and to search for a unified model that reproduces the observed signal best in a wide variety of stars. We then aim to define empirical scaling relations between the granulation properties and ν max and various other stellar parameters. Methods. We use a probabilistic method to compare different approaches to extracting the granulation signal. We fit the power density spectra of a large set of Kepler targets, determine the granulation and global oscillation parameter, and quantify scaling relations between them. Results. We establish that a depression in power at about ν max /2, known from the Sun and a few other main-sequence stars, is also statistically significant in red giants and that a super-Lorentzian function with two components is best suited to reproducing the granulation signal in the broader vicinity of the pulsation power excess. We also establish that the specific choice of the background model can affect the determination of ν max , introducing systematic uncertainties that can significantly exceed the random uncertainties. We find the characteristic frequency (i.e., inverse timescale) and amplitude of both background components to tightly scale with ν max for a wide variety of stars (about 2-2000 μHz in ν max ), and quantify a mass dependency of the latter. To enable comparison with theoretical predictions (which do not include the observed power depression), we computed effective timescales and bolometric intensity fluctuations and found them to approximately scale as τ eff ∝ g −0.85 T −0.4 and A gran ∝ (g 2 M) −1/4 (or more conveniently R/M 3/4 ), respectively. Similarly, the bolometric pulsation amplitude scales approximately as A puls ∝ (g 2 M) −1/3 (or R 4/3 /M), which implicitly verifies a separate mass and luminosity dependence of A puls . We have also checked our scaling relations with solar reference values and find them in good agreement. Conclusions. We provide a thorough analysis of the granulation background signal in a large sample of stars, from which we establish a unified model that allows us to accurately extract the granulation and global oscillation parameter. The resulting scaling relations allow a simple estimate of the overall spectral shape of any solar-ty...

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“…11) confirms its early-AGB status. The seismic properties were derived by Kallinger et al (2010b). As shown by Miglio (2012), using the interferometric radius does not significantly change the stellar mass.…”

Section: Carbon Isotopic Ratiomentioning

confidence: 99%

Models of red giants in the CoRoT asteroseismology fields combining asteroseismic and spectroscopic constraints

Lagarde

Miglio

Eggenberger

et al. 2015

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Context. The availability of asteroseismic constraints for a large sample of red giant stars from the CoRoT and Kepler missions paves the way for various statistical studies of the seismic properties of stellar populations. Aims. We use a detailed spectroscopic study of 19 CoRoT red giant stars to compare theoretical stellar evolution models to observations of the open cluster NGC 6633 and field stars. Methods. In order to explore the effects of rotation-induced mixing and thermohaline instability, we compare surface abundances of carbon isotopic ratio and lithium with stellar evolution predictions. These chemicals are sensitive to extra-mixing on the red giant branch. Results. We estimate mass, radius, and distance for each star using the seismic constraints. We note that the Hipparcos and seismic distances are different. However, the uncertainties are such that this may not be significant. Although the seismic distances for the cluster members are self consistent they are somewhat larger than the Hipparcos distance. This is an issue that should be considered elsewhere. Models including thermohaline instability and rotation-induced mixing, together with the seismically determined masses can explain the chemical properties of red giant targets. However, with this sample of stars we cannot perform stringent tests of the current stellar models. Tighter constraints on the physics of the models would require the measurement of the core and surface rotation rates, and of the period spacing of gravity-dominated mixed modes. A larger number of stars with longer times series, as provided by Kepler or expected with Plato, would help ensemble asteroseismology.

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Oscillating red giants in the CoRoT exofield: asteroseismic mass and radius determination

Cited by 183 publications

References 40 publications

Amplitudes of solar-like oscillations in red giant stars

Amplitudes of solar-like oscillations in red giant stars

The connection between stellar granulation and oscillation as seen by theKeplermission

Models of red giants in the CoRoT asteroseismology fields combining asteroseismic and spectroscopic constraints

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