Asteroseismology of main-sequence F stars with <i>Kepler</i>: overcoming short mode lifetimes

Compton, Douglas L.; Bedding, Timothy R.; Stello, Dennis

doi:10.1093/mnras/stz432

Cited by 12 publications

(8 citation statements)

References 67 publications

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“…The precision of the observed oscillation frequencies of F stars is poor in comparison to other stars in the LEGACY sample because of their large linewidths (see e.g. Appourchaux et al 2012;Lund et al 2017;Compton et al 2019), however their large amplitude of the helium signature effectively compensates for the lower precision.…”

Section: Average Amplitude Of Helium Signaturementioning

confidence: 99%

Helium settling in F stars: constraining turbulent mixing using observed helium glitch signature

Verma

Aguirre

2019

Monthly Notices of the Royal Astronomical Society

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Recent developments in asteroseismology -thanks to space-based missions such as CoRoT and Kepler -provide handles on those properties of stars that were either completely inaccessible in the past or only poorly measured. Among several such properties is the surface helium abundance of F and G stars. We used the oscillatory signature introduced by the ionization of helium in the observed oscillation frequencies to constrain the amount of helium settling in F stars. For this purpose, we identified three promising F stars for which the standard models of atomic diffusion predict large settling (or complete depletion) of surface helium. Assuming turbulence at the base of envelope convection zone slows down settling of the helium and heavy elements, we found an envelope mixed mass of approximately 5 × 10 −4 M ⊙ necessary to reproduce the observed amplitude of helium signature for all the three stars. This is much larger than the mixed mass of the order of 10 −6 M ⊙ found in the previous studies performed using the measurements of the heavy element abundances. This demonstrates the potential of using the helium signature together with measurements of the heavy element abundances to identify the most important physical processes competing against atomic diffusion, allowing eventually to correctly interpret the observed surface abundances of hot stars, consistent use of atomic diffusion in modelling both hot and cool stars, and shed some light on the long-standing cosmological lithium problem.

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Section: Average Amplitude Of Helium Signaturementioning

confidence: 99%

Helium settling in F stars: constraining turbulent mixing using observed helium glitch signature

Verma

Aguirre

2019

Monthly Notices of the Royal Astronomical Society

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“…It is perhaps no coincidence that targets in question are both F-stars and suffer from short mode lifetimes and potentially attenuation from magnetic fields (Broomhall et al 2015, recall HD 181906 has strong magnetic fields). The low asteroseismic precision and resultant large linewidths make mode identification difficult, as evidenced by the series of papers on HD 49933 (see also White et al 2012) and these difficulties have motivated novel methods of analysis such as using mode centroids (Bedding et al 2010;Compton et al 2019).…”

Section: Asteroseismic Inferencementioning

confidence: 99%

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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“…An abnormal rotation profile or stellar structure may also be identified using asteroseismology (e.g. Compton et al 2019;Beck et al 2012;Córsico 2018).…”

Section: Introductionmentioning

confidence: 99%

Looks can be deceiving

Temmink

Toonen

Zapartas

et al. 2020

A&A

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Context. White dwarfs (WDs) are important and abundant tools to study the structure and evolution of the Galactic environment. However, the multiplicity of WD progenitors is generally neglected. Specifically, a merger in a binary system can lead to a single WD, which could result in wrongly inferred quantities if only single stellar evolution (SSE) is considered. These mergers are linked to transients such as luminous red novae and Type Ia supernovae. Aims. We investigate the impact of binary evolution (BE) upon observable single WDs, and compare their properties to WDs formed through SSE. We assess the evolutionary channels and the age and mass distributions of the resulting single WDs. Methods. We employed SeBa to model the evolution of single star and binary populations. We synthesised the observable single WD population within 100 pc, including cooling and observational selection effects. Additionally, we constructed models with different evolution and primordial population properties to study the effects on the properties of the resulting single WDs. Results. White dwarfs from binary mergers make up about 10−30% of all observable single WDs and 30−50% of massive WDs. On average, individual WDs take 3.1−5 times longer to form through BE than SE, and so appear ∼1 Gyr younger than they are if BE is ignored. In all models, the effect of mergers on the age distribution is clearly noticeable. The median age typically increases by 85−430 Myr and 200−390 Myr for massive WDs. Although abundant, we do not find evidence that WDs from mergers significantly alter the shape of the WD mass distribution. Conclusions. Assuming SSE for inferring properties of single WDs gives rise to intrinsic errors as single WDs can also be formed following a binary merger. Strategies for mitigating the effect of mergers on the WD age distributions are discussed.

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Asteroseismology of main-sequence F stars with Kepler: overcoming short mode lifetimes

Cited by 12 publications

References 67 publications

Helium settling in F stars: constraining turbulent mixing using observed helium glitch signature

Helium settling in F stars: constraining turbulent mixing using observed helium glitch signature

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

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