Asteroseismic modelling of the solar-type subgiant star<i>β</i> Hydri

Brandão, I. M.; Doğan, G.; Christensen‐Dalsgaard, J.; Cunha, M. S.; Bedding, Timothy R.; Metcalfe, T. S.; Kjeldsen, H.; Bruntt, H.; Arentoft, T.

doi:10.1051/0004-6361/201015370

Cited by 55 publications

(58 citation statements)

References 40 publications

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“…4 and Table 4. Kjeldsen et al (2008) propose b = 4.90 in the case of the Sun, and many studies have adopted this value for other stars (e.g., Christensen-Dalsgaard et al 2010;Dogan et al 2010Dogan et al , 2013Metcalfe et al 2010;Tang & Gai 2011;Brandão et al 2011;Van Eylen et al 2012;Gilliland et al 2013;Gruberbauer et al 2013). When b is fixed, a simple fit provides the value of a (Kjeldsen et al 2008).…”

Section: Parameters Across the T Eff -G Planementioning

confidence: 99%

Surface-effect corrections for solar-like oscillations using 3D hydrodynamical simulations

Sonoi

Samadi

Belkacem

et al. 2015

A&A

114

246

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Context. The CoRoT and Kepler space-borne missions have provided us with a wealth of high-quality observational data that allows for seismic inferences of stellar interiors. This requires the computation of precise and accurate theoretical frequencies, but imperfect modeling of the uppermost stellar layers introduces systematic errors. To overcome this problem, an empirical correction has been introduced by Kjeldsen et al. (2008, ApJ, 683, L175) and is now commonly used for seismic inferences. Nevertheless, we still lack a physical justification allowing for the quantification of the surface-effect corrections. Aims. Our aim is to constrain the surface-effect corrections across the Hertzsprung-Russell (HR) diagram using a set of 3D hydrodynamical simulations. Methods. We used a grid of these simulations computed with the CO 5 BOLD code to model the outer layers of solar-like stars. Upper layers of the corresponding 1D standard models were then replaced by the layers obtained from the horizontally averaged 3D models. The frequency differences between these patched models and the 1D standard models were then calculated using the adiabatic approximation and allowed us to constrain the Kjeldsen et al. power law, as well as a Lorentzian formulation. Results. We find that the surface effects on modal frequencies depend significantly on both the effective temperature and the surface gravity. We further provide the variation in the parameters related to the surface-effect corrections using their power law as well as a Lorentzian formulation. Scaling relations between these parameters and the elevation (related to the Mach number) is also provided. The Lorentzian formulation is shown to be more robust for the whole frequency spectrum, while the power law is not suitable for the frequency shifts in the frequency range above ν max . Finally, we show that, owing to turbulent pressure, the elevation of the uppermost layers modifies the location of the hydrogen ionization zone and consequently introduces glitches in the surface effects for models with high (low) effective temperature (surface gravity). Conclusions. Surface-effect corrections vary significantly across the HR diagram. Therefore, empirical relations like those by Kjeldsen et al. must not be calibrated on the Sun but should instead be constrained using realistic physical modeling as provided by 3D hydrodynamical simulations.

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Section: Parameters Across the T Eff -G Planementioning

confidence: 99%

Surface-effect corrections for solar-like oscillations using 3D hydrodynamical simulations

Sonoi

Samadi

Belkacem

et al. 2015

A&A

114

246

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“…We followed the procedure of Brandão et al (2011). Kjeldsen et al obtained a value of b SE, = 4.9 when adjusting the relation on solar radial modes frequencies.…”

Section: Calculation Of Oscillation Frequenciesmentioning

confidence: 99%

Asteroseismology for “à la carte” stellar age-dating and weighing

Lebreton

Goupil

2014

A&A

157

168

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Context. In the context of the space missions CoRoT, Kepler, Gaia, TESS, and PLATO, precise and accurate stellar ages, masses, and radii are of paramount importance. For instance, they are crucial for constraining scenarii of planetary formation and evolution. Aims. We aim at quantifying how detailed stellar modelling can improve the accuracy and precision on age and mass of individual stars. To that end, we adopt a multifaceted approach where we carefully examine how the number of observational constraints as well as the uncertainties on observations and on model input physics affect the results of age-dating and weighing. Methods. We modelled in detail the exoplanet host-star HD 52265, a main-sequence, solar-like oscillator that CoRoT observed for four months. We considered different sets of observational constraints (Hertzsprung-Russell data, metallicity, various sets of seismic constraints). For each case, we determined the age, mass, and properties of HD 52265 inferred from stellar models, and we quantified the impact of the model input physics and free parameters. We also compared model ages with ages derived by empirical methods or Hertzsprung-Russell diagram inversion. Results. For our case study HD 52265, our seismic analysis provides an age A = 2.10−2.54 Gyr, a mass M = 1.14−1.32 M , and a radius R = 1.30−1.34 R , which corresponds to age, mass, and radius uncertainties of ∼10, ∼7, and ∼1.5 per cent, respectively. These uncertainties account for observational errors and current state-of-the-art stellar model uncertainties. Our seismic study also provides constraints on surface convection properties through the mixing-length, which we find to be 12−15 per cent lower than the solar value. On the other hand, because of helium-mass degeneracy, the initial helium abundance is determined modulo the mass value. Finally, we evaluate the seismic mass of the exoplanet to be M p sin i = 1.17−1.26 M Jupiter , much more precise than what can be derived by Hertzsprung-Russell diagram inversion. Conclusions. We demonstrate that asteroseismology allows us to substantially improve the age accuracy that can be achieved with other methods. We emphasize that the knowledge of the mean properties of stellar oscillations -such as the large frequency separation -is not enough to derive accurate ages. We need precise individual frequencies to narrow the age scatter that is a result of the model input physics uncertainties. Further progress is required to better constrain the physics at work in stars and the stars helium content. Our results emphasize the importance of precise classical stellar parameters and oscillation frequencies such as will be obtained by the Gaia and PLATO missions.

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“…The presence and identification of this kind of modes provides a stringent constraint on the internal properties of the star and on its evolutionary state. Although its potential has been already investigated in the case of η Bootis (di Mauro et al, 2004), 12 Bootis (Miglio et al, 2007), and β Hydri (Brandão et al, 2011), an unambiguous identification of mixed modes and its use in fitting stellar parameters became possible only recently with the high precision photometric data provided by CoRoT and Kepler Deheuvels & Michel, 2011;Metcalfe et al, 2010;Deheuvels & Michel, 2011;Mathur et al, 2011;Benomar et al, 2012;Doǧan et al, 2013). HD 49385 is a G0-type star with an apparent magnitude of m V = 7.39 (Hauck & Mermilliod, 1998) which was observed by CoRoT over a period of 137 days.…”

Section: An Exoplanet Host With Observed Planetary Transit Hd 17156mentioning

confidence: 99%