Convection and Overshoot in Models of γ Doradus and δ Scuti Stars

Lovekin, Catherine; Guzik, Joyce A.

doi:10.3847/1538-4357/aa8e01

Cited by 18 publications

(18 citation statements)

References 40 publications

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“…To determine the exact nature of F2, detailed seismic modelling and multi-color photometric observations are still required. We note such models about the period ratios are still lacking (Lovekin & Guzik 2017;Daszyńska-Daszkiewicz et al 2020;Rodríguez-Martín et al 2020). We suggest more studies of models (linear or nonlinear) investigating expected period ratios and effects on input physics for HADS stars should be undertaken.…”

Section: O −C Diagrammentioning

confidence: 95%

KIC 10975348: A Double-mode or Triple-mode High-amplitude δ Scuti Star?

Yang

Sun

Zuo

et al. 2020

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In this paper, we analyze the light variations of KIC 10975348 using photometric data delivered from the Kepler mission. This star is exceptionally faint (K p = 18.6 mag) compared to most well-studied δ Scuti stars. The Fourier analysis of the short-cadence data (i.e., Q14, Q15, and Q16, spanning 220 days) reveals that the variations are dominated by the strongest mode with a frequency of F0 = 10.231899 day−1, which is compatible with that obtained from RATS–Kepler. The other two independent modes with F1 (=13.4988 day−1) and F2 (=19.0002 day−1) are newly detected and have amplitudes two orders of magnitude smaller than F0. We note that, for the first time, this star is identified to be a high-amplitude δ Sct (HADS) star with an amplitude of about 0.7 mag, and the lower ratio of F0/F1 = 0.758 suggests that it might be a metal-rich variable star. The frequency F2 may be a third overtone mode, suggesting that this target might be a new radial triple-mode HADS star. We perform an O − C analysis using 1018 newly determined times of maximum light and derive an ephemeris formula of T max = 2456170.241912(0)+0.097734(1) × E. The O − C diagram shows that the pulsation period of KIC 10975348 seems to show no obvious change, which is in contrast to that of the majority of HADS stars. The possible cause of that may be due to the current short time span of the observations. To verify its possible period variations, regular observation from space with a longer time span in the future is needed.

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Section: O −C Diagrammentioning

confidence: 95%

KIC 10975348: A Double-mode or Triple-mode High-amplitude δ Scuti Star?

Yang

Sun

Zuo

et al. 2020

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“…Using photometric observations, the parameters of eclipsing binaries can be measured to a high degree of precision, which enables us to test theories and make predictions with tight constraints and greater certainty (Southworth 2019). Past research into stellar core convection suggests that there must be some overshoot beyond the theoretical convective boundary (Lovekin & Guzik 2017;Pedersen et al 2018;Johnston 2021), but the behaviour of overshoot as * Released on August, 20th, 2021 a function of stellar characteristics such as mass, age, or metallicity, has not yet been fully characterized. Since overshoot can be studied by examining pulsation modes through astroseismology, any star for which we can perform pulsation analysis provides insight into how overshoot varies.…”

Section: Introductionmentioning

confidence: 99%

Using Computational Models to Uncover the Parameters of Three Kepler Binaries: KIC 5957123, KIC 8314879, and KIC 10727668

Odesse,

Lovekin

2022

Preprint

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Theories of stellar convective core overshoot can be examined through analysis of pulsating stars. Better accuracy can be achieved by obtaining external constraints such as those provided by observing pulsating stars in eclipsing binary systems, but this requires that the binary parameters be identified so photometric variations of the pulsating component may be isolated from the binary periodicity. This study aims to uncover the physical parameters of three binaries observed by the Kepler spacecraft. We also seek to evaluate the feasibility of accurately constraining binaries using only readily available time-series photometry and distance estimates. Binary models were constructed using the Physics of Eclipsing Binaries (PHOEBE) software package. Markov Chain Monte Carlo methods were used to sample the parameter space of these models and provide estimates of the posterior distributions for these systems. An initial run using binned light curve data was performed to identify general parameter trends and provide initializing distributions for a subsequent analysis incorporating the full data set. We present theoretical models for all three binaries, along with posterior distributions from our MCMC analyses. Models for KIC 8314879 and KIC 10727668 produced a good match to the observed data, while the model of KIC 5957123 failed to generate an appropriate synthetic light curve. For the two successful models, we interpret the posterior distributions and discuss confidence in our parameter estimates and uncertainties. We also evaluate the feasibility of this procedure in various contexts, and propose several modifications to improve the success of future studies.

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“…More recently, Lovekin & Guzik (2017) studied the behaviour of convective overshoot in models of δ Scuti and γ Doradus stars between 1.2 M ⊙ and 2.2 M ⊙ . They found a strong correlation between the models pulsation constants as a function of effective temperature and their convective overshoot.…”

Section: Introductionmentioning

confidence: 99%

“…The temperature at which the convection zones begin to expand, log T ef f = 3.83, corresponds to the break point found in the log Q − log T ef f relationship. Lovekin & Guzik (2017) proposed that m low could be measured for radially-pulsating δ Scuti stars, and could be used to constrain the average convective overshoot parameter for a sample of stars.…”

Section: Introductionmentioning

confidence: 99%

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The Effects of Metallicity on Convective Overshoot Behaviour in Models of delta Scuti Variable Stars

Dornan,

Lovekin

2021

Preprint

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δ Scuti variables are stars which exhibit periodic changes in their luminosity through radial and non-radial pulsations. Internally, these stars have relatively small convective cores, and convective overshoot can significantly affect the size. Recently, models of radial pulsation in δ Scuti stars found a strong correlation between the pulsation constant (Q) as a function of effective temperature and the amount of convective overshoot within the star. However, only models with metallicities of Z = 0.02 were examined, leaving the dependence of this relationship on chemical composition unknown. In this work, we have extended the model grid to cover a range of metallicities using MESA, and analyzed the models' pulsation properties using GYRE. By varying the models' mass, rotation speed, convective overshoot, and metallicity, we studied the behaviour of Q at low temperature. We found that the updated convective boundary treatment in MESA changes the overshoot dependence found previously, and the value of the slope depends on both rotation and overshoot. We also found that there is a metallicity dependence in the Q values. The lowest metallicity models in our grid reached higher temperatures than previously studied, revealing a parabolic relation between log Q and log T ef f .

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Convection and Overshoot in Models of γ Doradus and δ Scuti Stars

Cited by 18 publications

References 40 publications

KIC 10975348: A Double-mode or Triple-mode High-amplitude δ Scuti Star?

KIC 10975348: A Double-mode or Triple-mode High-amplitude δ Scuti Star?

Using Computational Models to Uncover the Parameters of Three Kepler Binaries: KIC 5957123, KIC 8314879, and KIC 10727668

The Effects of Metallicity on Convective Overshoot Behaviour in Models of delta Scuti Variable Stars

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