An in-Depth Study of Grid-Based Asteroseismic Analysis

Gai, Ning; Basu, Sarbani; Chaplin, W. J.; Elsworth, Y.

doi:10.1088/0004-637x/730/2/63

Cited by 178 publications

(230 citation statements)

References 39 publications

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“…For 3 models, the age of the binary system is in the range 3.4-3.9 Gyr while for Ball the age is about 2.7 Gyr. All models return a very consistent log g for either star; this is the result of the very tight correlation between M and R as shown by (Gai et al 2011). …”

Section: Discussionsupporting

confidence: 58%

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: Discussionsupporting

confidence: 58%

A seismic and gravitationally bound double star observed byKepler

Appourchaux

Antia

Ball

et al. 2015

A&A

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“…These values can be used to derive a first estimate of the stellar mass and radius using scaling relations. Gai et al (2011) noted that since the errors in these estimates of the mass and radius are positively correlated, the error we obtain in the quantity M/R 2 and thus in log g is small. We report in Table 1 the estimated values of M, R, and log g, which are later confronted with those of our best-fit models.…”

Section: Seismic Constraintsmentioning

confidence: 59%

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

Deheuvels

Michel

2011

A&A

116

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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“…For example, Stello et al (2009a) compared the radius determined from different automatic analyses using simulated data and find that the radius can be determined with a precision of 3%. Gai et al (2011) made a detailed study of grid-based methods for asteroseismology using simulated data and also solar data. They investigated the errors in the parameters and concluded that the surface gravity can be determined with practically no systematic bias.…”

Section: Introductionmentioning

confidence: 99%

Fundamental properties of fiveKeplerstars using global asteroseismic quantities and ground-based observations

Creevey

Doğan

Frasca

et al. 2012

A&A

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We present an asteroseismic study of the solar-like stars KIC 11395018, KIC 10273246, KIC 10920273, KIC 10339342, and KIC 11234888 using short-cadence time series of more than eight months from the Kepler satellite. For four of these stars, we derive atmospheric parameters from spectra acquired with the Nordic Optical Telescope. The global seismic quantities (average large frequency separation and frequency of maximum power), combined with the atmospheric parameters, yield the mean density and surface gravity with precisions of 2% and ∼0.03 dex, respectively. We also determine the radius, mass, and age with precisions of 2-5%, 7-11%, and ∼35%, respectively, using grid-based analyses. Coupling the stellar parameters with photometric data yields an asteroseismic distance with a precision better than 10%. A v sin i measurement provides a rotational period-inclination correlation, and using the rotational periods from the recent literature, we constrain the stellar inclination for three of the stars. An Li abundance analysis yields an independent estimate of the age, but this is inconsistent with the asteroseismically determined age for one of the stars. We assess the performance of five grid-based analysis methods and find them all to provide consistent values of the surface gravity to ∼0.03 dex when both atmospheric and seismic constraints are at hand. The different grid-based analyses all yield fitted values of radius and mass to within 2.4σ, and taking the mean of these results reduces it to 1.5σ. The absence of a metallicity constraint when the average large frequency separation is measured with a precision of 1% biases the fitted radius and mass for the stars with non-solar metallicity (metal-rich KIC 11395018 and metal-poor KIC 10273246), while including a metallicity constraint reduces the uncertainties in both of these parameters by almost a factor of two. We found that including the average small frequency separation improves the determination of the age only for KIC 11395018 and KIC 11234888, and for the latter this improvement was due to the lack of strong atmospheric constraints.

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An in-Depth Study of Grid-Based Asteroseismic Analysis

Cited by 178 publications

References 39 publications

A seismic and gravitationally bound double star observed byKepler

A seismic and gravitationally bound double star observed byKepler

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

Fundamental properties of fiveKeplerstars using global asteroseismic quantities and ground-based observations

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