Asteroseismic Estimate of Helium Abundance of a Solar Analog Binary System

Verma, Kuldeep Chand; Faria, J. P.; Antia, H. M.; Basu, Sarbani; Mazumdar, A.; Monteiro, M. J. P. F. G.; Appourchaux, T.; Chaplin, W. J.; García, R. A.; Metcalfe, T. S.

doi:10.1088/0004-637x/790/2/138

Cited by 67 publications

(145 citation statements)

References 60 publications

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“…The asteroseismic results are taken from Metcalfe et al (2012), their results being a collaborative effort using a number of different stellar evolution codes and detailed asteroseismic modelling approaches. The adopted age is consistent with other asteroseismic results from Gruberbauer et al (2013), ≈ 6.5 ± 0.3 Gyr, and Verma et al (2014), 6.6 ± 0.3 Gyr. Determination of the age of the system from spectroscopic parameters and isochrone fitting has produced age estimates greater than the asteroseismic results (e.g.…”

Section: Introductionsupporting

confidence: 90%

Asteroseismic inference on rotation, gyrochronology and planetary system dynamics of 16 Cygni

Davies

Chaplin

Farr

et al. 2014

Monthly Notices of the Royal Astronomical Society

113

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The solar analogs 16 Cyg A and 16 Cyg B are excellent asteroseismic targets in the Kepler field of view and together with a red dwarf and a Jovian planet form an interesting system. For these more evolved Sun-like stars we cannot detect surface rotation with the current Kepler data but instead use the technique of asteroseimology to determine rotational properties of both 16 Cyg A and B. We find the rotation periods to be 23.8 • , for A and B respectively. Together with these results we use the published mass and age to suggest that, under the assumption of a solar-like rotation profile, 16 Cyg A could be used when calibrating gyrochronology relations. In addition, we discuss the known 16 Cyg B star-planet eccentricity and measured low obliquity which is consistent with Kozai cycling and tidal theory.

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Section: Introductionsupporting

confidence: 90%

Asteroseismic inference on rotation, gyrochronology and planetary system dynamics of 16 Cygni

Davies

Chaplin

Farr

et al. 2014

Monthly Notices of the Royal Astronomical Society

113

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“…Furthermore, it does so directly without making comparisons with theoretical predictions from models (except for interpreting the amplitude of the feature in terms of He abundance; see e.g. Verma et al 2014b), thereby making the results model-independent. In contrast, the forward modelling approach is indirect and model-dependent since it ends up implicitly comparing glitch signatures present in the observations to those obtained in theoretical models.…”

Section: Group 2: Glitch Fitting Analysismentioning

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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“…In fact, surface chemical composition differences between Verma et al (2014) is the same, the scatter is larger for the B component, and if microscopic diffusion is included in the stellar models, it is also clear that surface chemical composition differences will be seen since this mixing will not have the same efficiency for stars of different masses 2 . Nevertheless, it should be noted that chemical composition differences between 16CygA and 16CygB are still under some debate since their existence has been claimed by Ramírez et al (2009) andTucci Maia et al (2014) as well as by previous studies (see Deliyannis et al 2000) but could not be confirmed by Schuler et al (2011) Moreover, these values depend on the reference solar metallicity assumed in the study since the observational constraint provided is the [Fe/H] value which must be translated in a Z X value using the Sun as a reference.…”

Section: Reference Modelsmentioning

confidence: 99%

“…-Constraints: individual small frequency separations d 0,2 d 1,3 , inverted mean density (ρ) for which conservative error bars of 0.005 g/cm 3 were considered, acoustic radius (τ) for which conservative error bars of 30 s were considered, present surface metallicity (Z f /X f ) from Ramírez et al (2009), present surface helium abundance (Y f ) from Verma et al (2014) and the effective temperature from Tucci Maia et al (2014), for which we considered error bars of 30 K. In total, we had 5 free parameters for 31 constraints. In addition to these constraints, we checked the values of the luminosity L, surface gravity log g and radius R after the forward modelling to see if they were consistent with the constraints from the literature.…”

Section: Reference Modelsmentioning

confidence: 99%

In-depth study of 16CygB using inversion techniques

Buldgen

Salmon

Reese

et al. 2016

A&A

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Context. The 16Cyg binary system hosts the solar-like Kepler targets with the most stringent observational constraints. Indeed, we benefit from very high quality oscillation spectra, as well as spectroscopic and interferometric observations. Moreover, this system is particularly interesting since both stars are very similar in mass but the A component is orbited by a red dwarf, whereas the B component is orbited by a Jovian planet and thus could have formed a more complex planetary system. In our previous study, we showed that seismic inversions of integrated quantities could be used to constrain microscopic diffusion in the A component. In this study, we analyse the B component in the light of a more regularised inversion. Aims. We wish to analyse independently the B component of the 16Cyg binary system using the inversion of an indicator dedicated to analyse core conditions, denoted t u . Using this independent determination, we wish to analyse any differences between both stars due to the potential influence of planetary formation on stellar structure and/or their respective evolution. Methods. First, we recall the observational constraints for 16CygB and the method we used to generate reference stellar models of this star. We then describe how we improved the inversion and how this approach could be used for future targets with a sufficient number of observed frequencies. The inversion results were then used to analyse the differences between the A and B components. Results. The inversion of the t u indicator for 16CygB shows a disagreement with models including microscopic diffusion and sharing the chemical composition previously derived for 16CygA. We show that small changes in chemical composition are insufficient to solve the problem but that extra mixing can account for the differences seen between both stars. We use a parametric approach to analyse the impact of extra mixing in the form of turbulent diffusion on the behaviour of the t u values. We conclude on the necessity of further investigations using models with a physically motivated implementation of extra mixing processes including additional constraints to further improve the accuracy with which the fundamental parameters of this system are determined.

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Asteroseismic Estimate of Helium Abundance of a Solar Analog Binary System

Cited by 67 publications

References 60 publications

Asteroseismic inference on rotation, gyrochronology and planetary system dynamics of 16 Cygni

Asteroseismic inference on rotation, gyrochronology and planetary system dynamics of 16 Cygni

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

In-depth study of 16CygB using inversion techniques

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