Constraining mixing processes in stellar cores using asteroseismology

Aguirre, V. Silva; Ballot, J.; Serenelli, Aldo; Weiß, Achim

doi:10.1051/0004-6361/201015847

Cited by 87 publications

(82 citation statements)

References 86 publications

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“…The high precision of extracted mode frequencies further allows the study of ionization zones and the convective envelope boundary from acoustic glitches (Houdek & Gough 2007;Silva Aguirre et al 2011;Mazumdar et al 2014;Verma et al 2014), and one may also learn about the physics of the excitation and damping of the oscillation modes from measured mode line widths, amplitudes, and visibilities (Houdek et al 1999;Houdek 2006;Samadi et al 2005Samadi et al , 2007Belkacem et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Standing on the Shoulders of Dwarfs: the Kepler Asteroseismic LEGACY Sample. I. Oscillation Mode Parameters

Lund

Aguirre

Davies

et al. 2017

ApJ

233

223

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The advent of space-based missions like Kepler has revolutionized the study of solar-type stars, particularly through the measurement and modeling of their resonant modes of oscillation. Here we analyze a sample of 66 Kepler main-sequence stars showing solar-like oscillations as part of the Kepler seismic LEGACY project. We use Kepler short-cadence data, of which each star has at least 12 months, to create frequency power spectra optimized for asteroseismology. For each star we identify its modes of oscillation and extract parameters such as frequency, amplitude, and line width using a Bayesian Markov chain Monte Carlo 'peak-bagging' approach. We report the extracted mode parameters for all 66 stars, as well as derived quantities such as frequency difference ratios, the large and small separations ∆ν and δν 02 ; the behavior of line widths with frequency and line widths at ν max with T eff , for which we derive parametrizations; and behavior of mode visibilities. These average properties can be applied in future peak-bagging exercises to better constrain the parameters of the stellar oscillation spectra. The frequencies and frequency ratios can tightly constrain the fundamental parameters of these solar-type stars, and mode line widths and amplitudes can test models of mode damping and excitation.

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Section: Introductionmentioning

confidence: 99%

Standing on the Shoulders of Dwarfs: the Kepler Asteroseismic LEGACY Sample. I. Oscillation Mode Parameters

Lund

Aguirre

Davies

et al. 2017

ApJ

233

223

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show abstract

“…It has been shown in previous studies that the small separations built with l = 0 and l = 1 modes are particularly sensitive to the structure of the core (Provost et al 2005;Deheuvels et al 2010b;Silva Aguirre et al 2011) and that their ratios r 010 to the large separations are nearly insensitive to the so-called near-surface effects (Roxburgh & Vorontsov 2003). In Sect.…”

Section: Introductionmentioning

confidence: 84%

“…3b. As mentioned by Silva Aguirre et al (2011), the trajectory of models in the (a 1 , a 0 ) plane depends in a complex way on the evolutionary stage, the size of the convective core, and the amplitude of the glitch in the sound speed. However, we can still broadly understand it.…”

Section: Evolutionary Tracks In Thementioning

confidence: 98%

Measuring the extent of convective cores in low-mass stars usingKeplerdata: toward a calibration of core overshooting

Deheuvels

Brandão

Aguirre

et al. 2016

A&A

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127

130

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Context. Our poor understanding of the boundaries of convective cores generates large uncertainties on the extent of these cores and thus on stellar ages. The detection and precise characterization of solar-like oscillations in hundreds of main-sequence stars by CoRoT and Kepler has given the opportunity to revisit this problem. Aims. Our aim is to use asteroseismology to consistently measure the extent of convective cores in a sample of main-sequence stars whose masses lie around the mass limit for having a convective core. Methods. We first tested and validated a seismic diagnostic that was proposed to probe the extent of convective cores in a modeldependent way using the so-called r 010 ratios, which are built with l = 0 and l = 1 modes. We applied this procedure to 24 low-mass stars chosen among Kepler targets to optimize the efficiency of this diagnostic. For this purpose, we computed grids of stellar models with both the Cesam2k and mesa evolution codes, where the extensions of convective cores were modeled either by an instantaneous mixing or as a diffusion process. Results. We found that 10 stars in our sample are in fact subgiants. Among the other targets, were able to unambiguously detect convective cores in eight stars, and we obtained seismic measurements of the extent of the mixed core in these targets with a good agreement between the Cesam2k and mesa codes. By performing optimizations using the Levenberg-Marquardt algorithm, we then obtained estimates of the amount of extra mixing beyond the core that is required in Cesam2k to reproduce seismic observations for these eight stars, and we showed that this can be used to propose a calibration of this quantity. This calibration depends on the prescription chosen for the extra mixing, but we found that it should also be valid for the code mesa, provided the same prescription is used. Conclusions. This study constitutes a first step toward calibrating the extension of convective cores in low-mass stars, which will help reduce the uncertainties on the ages of these stars.

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“…In the modelling using individual frequencies three pipelines were used: (1) the BASTA, where the frequency separation ratios r 010 and r 02 are used rather than individual frequencies directly (see Roxburgh & Vorontsov 2003;Silva Aguirre et al 2011) -we shall refer to this as BASTA2 to distinguish it from the use to BASTA with average seismic parameters; (2) the ASTEC Fitting method (ASTFIT) using evolutionary models from the Aarhus STellar Evolution Code (ASTEC Christensen-Dalsgaard 2008a) and frequencies from ADIPLS; (3) the Yale-Monte Carlo (Table 2). BASTA2 indicates model results obtained using ratios from individual frequencies.…”

Section: Seismic Modellingmentioning

confidence: 99%

Asteroseismic Properties of Solar-type Stars Observed with the NASAK2Mission: Results from Campaigns 1–3 and Prospects for Future Observations

Lund

Chaplin

Casagrande

et al. 2016

PASP

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We present an asteroseismic analysis of 33 solar-type stars observed in short cadence during Campaigns (C) 1-3 of the NASA K2 mission. We were able to extract both average seismic parameters and individual mode frequencies for stars with dominant frequencies up to ∼3300 µHz, and we find that data for some targets are good enough to allow for a measurement of the rotational splitting. Modelling of the extracted parameters is performed by using grid-based methods using average parameters and individual frequencies together with spectroscopic parameters. For the target selection in C3, stars were chosen as in C1 and C2 to cover a wide range in parameter space to better understand the performance and noise characteristics. For C3 we still detected oscillations in 73% of the observed stars that we proposed. Future K2 campaigns hold great promise for the study of nearby clusters and the chemical evolution and age-metallicity relation of nearby field stars in the solar neighbourhood. We expect oscillations to be detected in ∼388 short-cadence targets if the K2 mission continues until C18, which will greatly complement the ∼500 detections of solar-like oscillations made for short-cadence targets during the nominal Kepler mission. For ∼30 − 40 of these, including several members of the Hyades open cluster, we furthermore expect that inference from interferometry should be possible.

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Constraining mixing processes in stellar cores using asteroseismology

Cited by 87 publications

References 86 publications

Standing on the Shoulders of Dwarfs: the Kepler Asteroseismic LEGACY Sample. I. Oscillation Mode Parameters

Standing on the Shoulders of Dwarfs: the Kepler Asteroseismic LEGACY Sample. I. Oscillation Mode Parameters

Measuring the extent of convective cores in low-mass stars usingKeplerdata: toward a calibration of core overshooting

Asteroseismic Properties of Solar-type Stars Observed with the NASAK2Mission: Results from Campaigns 1–3 and Prospects for Future Observations

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