Pulsation in Intermediate-Mass Stars

Balona, L. A.

doi:10.3389/fspas.2018.00043

Cited by 8 publications

(17 citation statements)

References 44 publications

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“…For example, Balona et al (2015b) find that an opacity increase of about a factor of two near temperatures of 115,000 K (log T = 5.06) in the stellar envelope can result in instability of some lowfrequency modes, but this opacity bump also reduces the range of unstable high-frequency modes. Balona (2018) highlights theoretical and computational work by Xiong et al (2016) with a new treatment of time-dependent convection that allows δ Sct stars to pulsate in low-frequency modes.…”

Section: Discovery Highlightsmentioning

confidence: 99%

“…Gravity mode and inertial (r) mode period spacing patterns found in Kepler γ Dor stars, in some cases supplemented by δ Sct p modes for the hybrid pulsators, have since been used by many groups to determine core and envelope rotation profiles in these stars (see, e.g., Van Reeth et al, 2016, 2018Ouazzani et al, 2017;Li et al, 2019bLi et al, , 2020. Interior differential rotation has also been studied and confirmed in γ Dor stars using the mode spacing patterns by, e.g., Aerts et al (2017), Christophe et al (2018), andVan Reeth et al (2018).…”

Section: γ Doradus Breakthroughsmentioning

confidence: 99%

“…Several reviews on Kepler findings for δ Sct variables have already been written (see, e.g., Balona, 2018;Bowman and Kurtz, 2018), and a comprehensive review of the Kepler legacy for these stars is premature. Prior to Kepler, one of the best compilations of the state-of-the-art of research on δ Sct variables was the Handbook and Conference Proceedings volume δ Scuti and Related Stars (Breger and Montgomery, 2000).…”

Section: Introductionmentioning

confidence: 99%

“…The A-F main-sequence stars occupy a small region in the center of the H-R diagram, but have been differentiated into not only δ Sct and γ Doradus (abbreviated as γ Dor) variables (Pollard, 2009;Balona et al, 2011a), but also metallic-line A (Am) (Smalley et al, 2017), peculiar abundance A (Ap) (Mathys et al, 2020), rapidly-oscillating Ap (roAp) (Holdsworth, 2021) stars, α 2 CVn variables (Sikora et al, 2019), λ Boo stars (Murphy and Paunzen, 2017), the High Amplitude δ Sct (HADS) (McNamara, 2000) and SX Phe (Nemec et al, 2017) stars, blue stragglers (Rain et al, 2021), and the maybe "mythical" 1 Maia variables (Breger, 1980;Cox, 1983;Daszyńska-Daszkiewicz et al, 2017;White et al, 2017;Balona, 2018). Kepler observations have revealed overlap and commonalities among these types, pointing the way to a more fundamental understanding of the origins of the diverse phenomena seen in these stars.…”

Section: Introductionmentioning

confidence: 99%

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Highlights of Discoveries for δ Scuti Variable Stars From the Kepler Era

Guzik

2021

Front. Astron. Space Sci.

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The NASA Kepler and follow-on K2 mission (2009–2018) left a legacy of data and discoveries, finding thousands of exoplanets, and also obtaining high-precision long time-series data for hundreds of thousands of stars, including many types of pulsating variables. Here we highlight a few of the ongoing discoveries from Kepler data on δ Scuti pulsating variables, which are core hydrogen-burning stars of about twice the mass of the Sun. We discuss many unsolved problems surrounding the properties of the variability in these stars, and the progress enabled by Kepler data in using pulsations to infer their interior structure, a field of research known as asteroseismology.

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Section: Discovery Highlightsmentioning

confidence: 99%

Section: γ Doradus Breakthroughsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Highlights of Discoveries for δ Scuti Variable Stars From the Kepler Era

Guzik

2021

Front. Astron. Space Sci.

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“…δ Sct stars in which all significant frequency peaks in the periodogram are below 5 d −1 are called γ Doradus variables. It is, however, likely that the driving mechanism in the γ Dor stars is the same as in the δ Sct stars (Balona 2018). Guzik (2021) has presented an excellent review of the δ Sct stars, but fails to mention what is perhaps the most perplexing problem.…”

Section: Introductionmentioning

confidence: 99%

The mode selection problem in delta Scuti stars

Balona

2021

Preprint

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Inspection of the periodograms of 9597 TESS δ Scuti stars indicates that there is little, if any, correlation between the frequencies and location of the stars in the H-R diagram. A quantitative measure of similarity is described which can be used to compare two frequency spectra. When applied to non-adiabatic pulsation models, the expected strong correlation is found between the predicted pulsation frequencies for models with similar temperatures and luminosities. The correlation is maintained when rotational splitting is included. However, no correlation is found between the frequencies of TESS δ Scuti stars with similar effective temperatures and luminosities. As suspected, the observed frequencies do not depend on the stellar parameters, contradicting the models. This result suggests that an unknown mode selection process is active, presenting a fundamental problem in our current understanding of pulsational driving or the structure of the outer layers of stars with radiative atmospheres.

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High-amplitude γ Doradus variables

Paunzen

Bernhard

Hümmerich

et al. 2020

Monthly Notices of the Royal Astronomical Society

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According to most literature sources, the amplitude of the pulsational variability observed in γ Doradus stars does not exceed 0.1 mag in Johnson V. We have analyzed fifteen high-amplitude γ Doradus stars with photometric peak-to-peak amplitudes well beyond this limit, with the aim of unraveling the mechanisms behind the observed high amplitudes and investigating whether these objects are in any way physically distinct from their low-amplitude counterparts. We have calculated astrophysical parameters and investigated the location of the high-amplitude γ Doradus stars and a control sample of fifteen low-amplitude objects in the log Teff versus log L/L⊙ diagram. Employing survey data and our own observations, we analyzed the photometric variability of our target stars using discrete Fourier transform. Correlations between the observed primary frequencies, amplitudes and other parameters like effective temperature and luminosity were investigated. The unusually high amplitudes of the high-amplitude γ Doradus stars can be explained by the superposition of several base frequencies in interaction with their combination and overtone frequencies. Although the maximum amplitude of the primary frequencies does not exceed an amplitude of 0.1 mag, total light variability amplitudes of over 0.3 mag (V) can be attained in this way. Low- and high-amplitude γ Doradus stars do not appear to be physically distinct in any other respect than their total variability amplitudes but merely represent two ends of the same, uniform group of variables.

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Pulsation in Intermediate-Mass Stars

Cited by 8 publications

References 44 publications

Highlights of Discoveries for δ Scuti Variable Stars From the Kepler Era

Highlights of Discoveries for δ Scuti Variable Stars From the Kepler Era

The mode selection problem in delta Scuti stars

High-amplitude γ Doradus variables

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