Convective overshooting in the evolution and seismology of $\mathsf{\eta}$ Bootis

Mauro, M. P. Di; Christensen‐Dalsgaard, J.; Kjeldsen, H.; Bedding, Timothy R.; Paternò, L.

doi:10.1051/0004-6361:20030478

Cited by 62 publications

(63 citation statements)

References 19 publications

(20 reference statements)

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“…3). We have a problem that is quite commonplace for evolved objects: a degeneracy between MS models and PoMS models, which results in an uncertainty in the evolutionary stage of the studied object (see e.g., Procyon A in Barban et al 1999;Provost et al 2006; η Boo in Di Mauro et al 2003). The internal structure of these two families of models is very different.…”

Section: Evolutionary Status Of Hd 49385mentioning

confidence: 99%

Constraints on the structure of the core of subgiants via mixed modes: the case of HD 49385

Deheuvels

Michel

2011

A&A

114

165

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Context. The solar-like pulsator HD 49385 was observed with the CoRoT satellite over a period of 137 days. The analysis of its oscillation spectrum yielded precise estimates of the mode frequencies over nine radial orders and distinguished some unusual characteristics, such as some modes outside the identified ridges in the échelle diagram and that the curvature of the = 1 ridge differs significantly from that of the = 0 ridge. Aims. We search for stellar models that can reproduce the peculiar features of the oscillation spectrum of HD 49385. After showing that they can be accounted for only by a low-frequency = 1 avoided crossing, we investigate the information provided by the mixed modes about the structure of the core of HD 49385. Methods. We propose a toy-model to study the case of avoided crossings with a strong coupling between the p-mode and g-mode cavities in order to establish the presence of mixed modes in the spectrum of HD 49385. We then show that traditional optimization techniques are ill-suited to stars with mixed modes in avoided crossing. We propose a new approach to the computation of grids of models that we apply to HD 49385. Results. The detection of mixed modes leads us to establish the post-main-sequence status of HD 49385. The mixed mode frequencies suggest that there is a strong coupling between the p-mode and g-mode cavities. As a result, we show that the amount of core overshooting in HD 49385 is either very small (0 < α ov < 0.05) or moderate (0.18 < α ov < 0.20). The mixing length parameter is found to be significantly lower than the solar one (α CGM = 0.55 ± 0.04 compared to the solar value α = 0.64). Finally, we show that the revised solar abundances of Asplund ensure closer agreement with the observations than the classical ones of Grevesse & Noels. At each step, we investigate the origin and meaning of these seismic diagnostics in terms of the physical structure of the star. Conclusions. The subgiant HD 49385 is the first star for which a thorough modeling has been attempted to reproduce all the properties of an avoided crossing. It has provided the opportunity to show that the study of the coupling between the cavities in these stars can provide valuable insight into open questions such as core overshooting, the efficiency of convection, and the abundances of heavy elements in stars.

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Section: Evolutionary Status Of Hd 49385mentioning

confidence: 99%

Constraints on the structure of the core of subgiants via mixed modes: the case of HD 49385

Deheuvels

Michel

2011

A&A

114

165

View full text Add to dashboard Cite

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“…Initial efforts attempted to reproduce the observed large and small frequency separations with models that simultaneously matched constraints from spectroscopy (e.g., Christensen-Dalsgaard et al 1995;Thévenin et al 2002;Fernandes & Monteiro 2003;Thoul et al 2003). As individual oscillation frequencies became available, modelers started to match the observations in échelle diagrams that highlighted variations around the average frequency separations (e.g., Di Mauro et al 2003;Guenther & Brown 2004;Eggenberger et al 2004). This approach continued until the frequency precision from longer space-based observations became sufficient to reveal systematic errors in the models that are known as surface effects, which arise from incomplete modeling of the near-surface layers where the mixing-length treatment of convection is approximate.…”

Section: Introductionmentioning

confidence: 99%

Characterizing solar-type stars from full-length Kepler data sets using the Asteroseismic Modeling Portal

Creevey

Metcalfe

Schultheis

et al. 2017

A&A

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The Kepler space telescope yielded unprecedented data for the study of solar-like oscillations in other stars. The large samples of multi-year observations posed an enormous data analysis challenge that has only recently been surmounted. Asteroseismic modeling has become more sophisticated over time, with better methods gradually developing alongside the extended observations and improved data analysis techniques. We apply the latest version of the Asteroseismic Modeling Portal (AMP) to the full-length Kepler data sets for 57 stars, comprising planetary hosts, binaries, solar-analogs, active stars, and for validation purposes, the Sun. From an analysis of the derived stellar properties for the full sample, we identify a variation of the mixing-length parameter with atmospheric properties. We also derive a linear relation between the stellar age and a characteristic frequency separation ratio. In addition, we find that the empirical correction for surface effects suggested by Kjeldsen and coworkers is adequate for solar-type stars that are not much hotter (T eff < ∼ 6200 K) or significantly more evolved (log g > ∼ 4.2, ∆ν > ∼ 80 µHz) than the Sun. Precise parallaxes from the Gaia mission and future observations from TESS and PLATO promise to improve the reliability of stellar properties derived from asteroseismology.

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“…These mixed modes present dual characterisitics as they have kinetic energy both in the inner regions of the star (g mode nature) and in the outer layers (p mode nature). Such modes may have already been observed for the star ηBoo (Christensen-Dalsgaard et al 1995;Guenther & Demarque 1996;Di Mauro et al 2003). We expect that observation of such modes might help to determine the variation of the rotation profile along the radius and localize some possible strong rotational gradient.…”

Section: Introductionmentioning

confidence: 67%

Rotation profile inversion in solar-like stars

Lochard

Samadi

Goupil

2005

A&A

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Abstract. The observation of a few mixed modes on solar-like oscillating stars would enable their rotation profile to be inverted with success. Here simulated data are used to show that it is possible to find models for solar-like stars that present stochastically excited mixed modes with detectable amplitudes. We take special care to build the mode set by computing the mode amplitudes and selecting those modes with amplitudes compatible with the performance of the forthcoming seismic space experiment, COROT. The frequency set is inverted for various cases where input and trial stellar models differ and where random noise is added to the splittings. We show it is possible to localize a rotation gradient and assess its magnitude. Moreover the use of inverse and forward procedures in parallel gives access to a large part of the profile. We provide several constraints to help the selection of such stars. One looks for a relatively evolved star (still on the main sequence) of 1.5 M and the rotation rate on the surface should not be too small.

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Convective overshooting in the evolution and seismology of $\mathsf{\eta}$ Bootis

Cited by 62 publications

References 19 publications

Constraints on the structure of the core of subgiants via mixed modes: the case of HD 49385

Constraints on the structure of the core of subgiants via mixed modes: the case of HD 49385

Characterizing solar-type stars from full-length Kepler data sets using the Asteroseismic Modeling Portal

Rotation profile inversion in solar-like stars

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