ASTEROSEISMIC MODELING OF 16 Cyg A &amp; B USING THE COMPLETE
                    <i>KEPLER</i>
                    DATA SET

Metcalfe, T. S.; Creevey, O.; Davies, G. R.

doi:10.1088/2041-8205/811/2/l37

Cited by 77 publications

(83 citation statements)

References 48 publications

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“…These models include the effects of helium diffusion (Michaud & Proffitt 1993), but not overshoot. The same AMP configuration used in Metcalfe et al (2014) was also applied here; the updated physics and fitting methods described in Metcalfe et al (2015) were not employed. In particular, individual frequencies (including surface corrections based on Kjeldsen et al 2008) and frequency ratios were simultaneously used when searching for best-fitting models.…”

Section: Group 1: Forward Modelling Approachmentioning

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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Section: Group 1: Forward Modelling Approachmentioning

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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“…With the advent of the Kepler (Borucki et al 2010) and CoRoT (Baglin et al 2006) space missions, time series measuring stellar variability of very-high quality have become widely available. Analysis of these time series can deliver precise estimates of stellar ages Lebreton et al 2014;Meibom et al 2015;Metcalfe et al 2015;Miglio et al 2013b;Silva Aguirre et al 2015) -a quantity critical for reconstructing the history of the Milky Way. With the re-purposed Kepler mission K2 (Howell et al 2014) currently capturing solar-like oscillations Stello et al 2015) in a number of different galactic directions, and the future missions of TESS (Ricker et al 2014) and PLATO (Rauer et al 2014) adding to this, ages for many thousands of stars in many different galactic distances and directions present an exciting possibility.…”

Section: Introductionmentioning

confidence: 99%

Asteroseismology of red giants: From analysing light curves to estimating ages

Davies

Miglio

2016

Astron Nachr

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Asteroseismology has started to provide constraints on stellar properties that will be essential to accurately reconstruct the history of the Milky Way. Here we look at the information content in data sets representing current and future space missions (CoRoT, Kepler, K2, TESS, and PLATO) for red giant stars. We describe techniques for extracting the information in the frequency power spectrum and apply these techniques to Kepler data sets of different observing length to represent the different space missions. We demonstrate that for KIC 12008916, a low-luminosity red giant branch star, we can extract useful information from all data sets, and for all but the shortest data set we obtain good constraint on the g-mode period spacing and core rotation rates. We discuss how the high precision in these parameters will constrain the stellar properties of stellar radius, distance, mass and age. We show that high precision can be achieved in mass and hence age when values of the g-mode period spacing are available. We caution that tests to establish the accuracy of asteroseismic masses and ages are still "work in progress".

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“…After this paper was accepted, Travis Metcalfe draw our attention to his new article accepted for publication in ApJ "Asteroseismic modeling of 16 Cyg A & B using the complete Kepler data set" by Metcalfe et al (2015) The authors revise the data given in Metcalfe et al (2012), particularly the age (7.0 ± 0.3 Gyr) and the composition (Z = 0.021 ± 0.002, Yi = 0.25 ± 0.01). They acknowledge that the helium content they derive may be slightly underestimated due to their neglecting atomic diffusion of heavy elements in the models.…”

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confidence: 99%

Accretion of planetary matter and the lithium problem in the 16 Cygni stellar system

Deal

Richard

Vauclair

2015

A&A

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Context. The 16 Cygni system is composed of two solar analogues with similar masses and ages. A red dwarf is in orbit around 16 Cygni A, and 16 Cygni B hosts a giant planet. The abundances of heavy elements are similar in the two stars, but lithium is much more depleted in 16 Cygni B than in 16 Cygni A, by a factor of at least 4.7. Aims. The interest of studying the 16 Cygni system is that the two star have the same age and the same initial composition. The differences currently observed must be due to their different evolution, related to the fact that one of them hosts a planet while the other does not. Methods. We computed models of the two stars that precisely fit the observed seismic frequencies. We used the Toulouse Geneva Evolution Code (TGEC), which includes complete atomic diffusion (including radiative accelerations). We compared the predicted surface abundances with the spectroscopic observations and confirm that another mixing process is needed. We then included the effect of accretion-induced fingering convection. Results. The accretion of planetary matter does not change the metal abundances but leads to lithium destruction, which depends upon the accreted mass. A fraction of the Earth's mass is enough to explain the lithium surface abundances of 16 Cygni B. We also checked the beryllium abundances. Conclusions. In the case of accretion of heavy matter onto stellar surfaces, the accreted heavy elements do not remain in the outer convective zones, but are mixed downwards by fingering convection induced by the unstable μ-gradient. Depending on the accreted mass, this mixing process may transport lithium down to its nuclear destruction layers and lead to an extra lithium depletion at the surface. A fraction of the Earth's mass is enough to explain a lithium ratio of 4.7 in the 16 Cygni system. In this case beryllium is not destroyed. Such a process may be frequent in planet-hosting stars and should be studied in other cases in the future.

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ASTEROSEISMIC MODELING OF 16 Cyg A & B USING THE COMPLETE KEPLER DATA SET

Cited by 77 publications

References 48 publications

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

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

Asteroseismology of red giants: From analysing light curves to estimating ages

Accretion of planetary matter and the lithium problem in the 16 Cygni stellar system

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