A Bayesian approach to the modelling of α Cen A

Bazot, M.; Bourguignon, Sébastien; Christensen‐Dalsgaard, J.

doi:10.1111/j.1365-2966.2012.21818.x

Cited by 62 publications

(55 citation statements)

References 65 publications

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“…It is quite clear that while being correct from a statistical point of view, it slants the optimisation towards the seismic parameters. A Bayesian approach to this optimisation problem will take the classical parameters into account in a more realistic way such as in Bazot et al (2012).…”

Section: What Is Needed For Progress?mentioning

confidence: 99%

A seismic and gravitationally bound double star observed byKepler

Appourchaux

Antia

Ball

et al. 2015

A&A

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Context. Solar-like oscillations have been observed by Kepler and CoRoT in many solar-type stars, thereby providing a way to probe stars using asteroseismology. Aims. The derivation of stellar parameters has usually been done with single stars. The aim of the paper is to derive the stellar parameters of a double-star system (HIP 93511), for which an interferometric orbit has been observed along with asteroseismic measurements. Methods. We used a time series of nearly two years of data for the double star to detect the two oscillation-mode envelopes that appear in the power spectrum. Using a new scaling relation based on luminosity, we derived the radius and mass of each star. We derived the age of each star using two proxies: one based upon the large frequency separation and a new one based upon the small frequency separation. Using stellar modelling, the mode frequencies allowed us to derive the radius, the mass, and the age of each component. In addition, speckle interferometry performed since 2006 has enabled us to recover the orbit of the system and the total mass of the system. Results. From the determination of the orbit, the total mass of the system is 2.34 +0.45 −0.33 M . The total seismic mass using scaling relations is 2.47 ± 0.07 M . The seismic age derived using the new proxy based upon the small frequency separation is 3.5 ± 0.3 Gyr. Based on stellar modelling, the mean common age of the system is 2.7-3.9 Gyr. The mean total seismic mass of the system is 2.34-2.53 M consistent with what we determined independently with the orbit. The stellar models provide the mean radius, mass, and age of the stars as R A = 1.82−1.87 R , M A = 1.25−1.39 M , Age A = 2.6-3.5 Gyr; R B = 1.22−1.25 R , M B = 1.08−1.14 M , Age B = 3.35-4.21 Gyr. The models provide two sets of values for Star A: [1.25-1.27] M and [1.34-1.39] M . We detect a convective core in Star A, while Star B does not have any. For the metallicity of the binary system of Z ≈ 0.02, we set the limit between stars having a convective core in the range [1.14-1.25] M .

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Section: What Is Needed For Progress?mentioning

confidence: 99%

A seismic and gravitationally bound double star observed byKepler

Appourchaux

Antia

Ball

et al. 2015

A&A

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“…This has been done in various works (e.g. Bruntt et al 2010;Miglio & Montalbán 2005;Bazot et al 2012;Huber et al 2012;Silva Aguirre et al 2012) where stellar masses deduced from orbital parameters in binary systems and/or radii from a combination of astrometry and interferometry in nearby systems were used either as a test of seismic results or as supplementary constraints. An alternate approach is to carry out a hare-and-hounds exercise.…”

Section: Introductionmentioning

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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“…Thus, α Cen is an ideal laboratory for stellar evolution (e.g. Kervella et al 2003;Porto de Mello et al 2008;Bruntt et al 2010;Bazot et al 2012), asteroseismology (Kjeldsen et al 2008;de Meulenaer et al 2010) and extra-solar planet searches (Dumusque et al 2012;Rajpaul et al 2016;Bergmann et al 2015;Endl et al 2015). As such it is crucial to determine the properties of the two stars in α Cen with the highest accuracy, which can be done as double-lined spectroscopic visual binaries, thus offering a hypothesis-free determination of the distance and individual masses (Pourbaix 1998).…”

Section: Introductionmentioning

confidence: 99%

Parallax and masses ofαCentauri revisited

Pourbaix

Boffin

2016

A&A

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Context. Despite the thorough work of van Leeuwen, the parallax of α Centauri is still far from being carved in stone. Any derivation of the individual masses is therefore uncertain, if not questionable. And yet, that does not prevent this system from being used for calibration purpose in several studies. Aims. We aim for more accurate model-free parallax and individual masses of this system. Methods. With HARPS, the radial velocities are not only precise but also accurate. Ten years of HARPS data are enough to derive the complement of the visual orbit for a full 3D orbit of α Cen. Results. We locate α Cen (743 mas) right where Hipparcos had originally put it, i.e. slightly farther away than derived by Söderhjelm. The components are thus a bit more massive than previously thought (1.13 and 0.97 M for A and B, respectively). These values are now in excellent agreement with the latest asteroseismologic results.

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A Bayesian approach to the modelling of α Cen A

Cited by 62 publications

References 65 publications

A seismic and gravitationally bound double star observed byKepler

A seismic and gravitationally bound double star observed byKepler

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

Parallax and masses ofαCentauri revisited

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