ASTEROSEISMIC ANALYSIS OF THE<i>CoRoT</i>TARGET HD 49933

Liu, Zhi-E; Yang, Wuming; Bi, Shaolan; Tian, Zhijia; Liu, Kang; Ge, Zhishuai; Jiang, Yu; Li, Tanda; Tan, Xiaoyan; He, Xin; Wu, Yaqian; Chintarungruangchai, P.

doi:10.1088/0004-637x/780/2/152

Cited by 17 publications

(46 citation statements)

References 48 publications

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“…We emphasise that all these models with χ 2 ≤ 1 fit the data, there is no justification for taking the models with the lowest χ 2 as the best fit model. The wide range of models that fit the data is compatible with the wide range of model fits reported by Piau et al (2009), Benomar et al (2010, Kallinger et al (2010), Bigot et al (2011), Creevey & Bazot (2011), and Liu et al (2014 whose best fit models vary in mass between 1.12−1.35 M , ages between 2.15−3.25 × 10 9 yr and Z values between 0.005−0.20. In their analyses Kallinger et al (2010), and Liu et al (2014) used only modes of degree = 0, 1, since the error estimates on = 2 modes are very large (>2 µHz).…”

Section: Hd 49933supporting

confidence: 84%

Surface layer independent model fitting by phase matching: theory and application to HD 49933 and HD 177153 (aka Perky)

Roxburgh

2015

A&A

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Aims. Our aim is to describe the theory of surface layer independent model fitting by phase matching and to apply this to the stars HD 49933 observed by CoRoT, and HD 177153 (aka Perky) observed by Kepler. Methods. We use theoretical analysis, phase shifts, and model fitting. Results. We define the inner and outer phase shifts of a frequency set of a model star and show that the outer phase shifts are (almost) independent of degree , and that a function of the inner phase shifts (the phase function) collapses to an independent function of frequency in the outer layers. We then show how to use this result in a model fitting technique to find a best fit model to an observed frequency set by calculating the inner phase shifts of a model using the observed frequencies and determining the extent to which the phase function collapses to a single function of frequency in the outer layers. This technique does not depend on the radial order n assigned to the observed frequencies. We give two examples applying this technique to the frequency sets of HD 49933 observed by CoRoT and HD 177153 (aka Perky) observed by Kepler, for which measurements of angular diameters and bolometric fluxes are available. For HD 49933 we find a very wide range of models to be consistent with the data (all with convective core overshooting) -and conclude that the data is not precise enough to make any useful restrictions on the structure of this star. For HD 177153 our best fit models have no convective cores, masses in the range 1.15−1.17 M , ages of 4.45−4.70 × 10 9 yr, Z in the range 0.021−0.024, XH = 0.71−0.72, Y = 0.256−0.266 and mixing length parameter α = 1.8. We compare our results to those of previous studies. We contrast the phase matching technique to that using the ratios of small to large separations, showing that it avoids the problem of correlated errors in separation ratio fitting and of assigning radial order n to the modes.

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Section: Hd 49933supporting

confidence: 84%

Surface layer independent model fitting by phase matching: theory and application to HD 49933 and HD 177153 (aka Perky)

Roxburgh

2015

A&A

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“…We are motivated by the fact that asteroseismic fitting can result in CBM efficiencies far higher than those inferred from well-tried calibration methods such as fitting to binaries or clusters. Typically an extension of the mixed region above the convective core of 0.1 − 0.3H P is required in these systems Rosenfield et al 2017) whereas, in some cases, factors two to five times larger have been found from asteroseismic inference (see for example Liu et al 2014;Guenther et al 2014 and our results below). There is also contention as to whether the efficiency of CBM exhibits a linear dependency with mass (at M < 2.0M ), with several calibration studies arriving at opposing conclusions Constantino & Baraffe 2018;Claret & Torres 2018).…”

Section: Introductionmentioning

confidence: 49%

“…The provided frequency lists were subsequently used by several groups in order to characterize HD 49933 in detail. Liu et al (2014) and Roxburgh (2015) generated large grids of models with different input physics and demonstrated that a wide spread of models are consistent with the data. The latter explicitly concluding the precision on the frequencies (Figure 4) is not good enough to constrain the large number of possible models.…”

Section: A Closer Look At Hd 49933 and Hd 181906mentioning

confidence: 88%

Convective boundary mixing in low- and intermediate-mass stars – I. Core properties from pressure-mode asteroseismology

Angelou

Bellinger

Hekker

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Convective boundary mixing (CBM) is ubiquitous in stellar evolution. It is a necessary ingredient in the models in order to match observational constraints from clusters, binaries and single stars alike. We compute 'effective overshoot' measures that reflect the extent of mixing and which can differ significantly from the input overshoot values set in the stellar evolution codes. We use constraints from pressure modes to infer the CBM properties of Kepler and CoRoT main-sequence and subgiant oscillators, as well as in two radial velocity targets (Procyon A and α Cen A). Collectively these targets allow us to identify how measurement precision, stellar spectral type, and overshoot implementation impact the asteroseismic solution. With these new measures we find that the 'effective overshoot' for most stars is in line with physical expectations and calibrations from binaries and clusters. However, two F-stars in the CoRoT field (HD 49933 and HD 181906) still necessitate high overshoot in the models. Due to short mode lifetimes, mode identification can be difficult in these stars. We demonstrate that an incongruence between the radial and non-radial modes drives the asteroseismic solution to extreme structures with highly-efficient CBM as an inevitable outcome. Understanding the cause of seemingly anomalous physics for such stars is vital for inferring accurate stellar parameters from TESS data with comparable timeseries length.

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“…The models of the four stars were determined Liu et al 2014;Yang et al 2015;Yang 2015). The radius of the convective core including overshooting region is around 0.056 R ⊙ for the model 14 1 http://www.originlab.com/doc/Origin-help/NLFit-theory of KIC 6225718 , 0.17 R ⊙ for the model M52 of HD 49933 , 0.358 R ⊙ for the model Ma14 of KIC 2837475 , and 0.37 R ⊙ for the model Ma6 of KIC 11081729 (Yang 2015).…”

Section: Estimate the Radius Of The Convective Core From Oscil-lationmentioning

confidence: 99%

Estimating the Radius of the Convective Core of Main-Sequence Stars From Observed Oscillation Frequencies

Yang

2016

ApJ

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The determination of the size of the convective core of main-sequence stars is usually dependent on the construction of models of stars. Here we introduce a method to estimate the radius of the convective core of main-sequence stars with masses between about 1.1 and 1.5 M ⊙ from observed frequencies of low-degree p-modes. A formula is proposed to achieve the estimation. The values of the radius of the convective core of four known stars are successfully estimated by the formula. The radius of the convective core of KIC 9812850 estimated by the formula is 0.140 ± 0.028 R ⊙ . In order to confirm this prediction, a grid of evolutionary models were computed. The value of the convective-core radius of the best-fit model of KIC 9812850 is 0.149 R ⊙ , which is in good agreement with that estimated by the formula from observed frequencies. The formula aids in understanding the interior structure of stars directly from observed frequencies. The understanding is not dependent on the construction of models.

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ASTEROSEISMIC ANALYSIS OF THECoRoTTARGET HD 49933

Cited by 17 publications

References 48 publications

Surface layer independent model fitting by phase matching: theory and application to HD 49933 and HD 177153 (aka Perky)

Surface layer independent model fitting by phase matching: theory and application to HD 49933 and HD 177153 (aka Perky)

Convective boundary mixing in low- and intermediate-mass stars – I. Core properties from pressure-mode asteroseismology

Estimating the Radius of the Convective Core of Main-Sequence Stars From Observed Oscillation Frequencies

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