Asteroseismic inference on rotation, gyrochronology and planetary system dynamics of 16 Cygni

Davies, G. R.; Chaplin, W. J.; Farr, W. M.; García, R. A.; Lund, Mikkel N.; Mathis, S.; Metcalfe, T. S.; Appourchaux, T.; Basu, Sarbani; Benomar, O.; Campante, Tiago L.; Ceillier, T.; Elsworth, Y.; Handberg, R.; Salabert, D.; Stello, Dennis

doi:10.1093/mnras/stu2331

Cited by 115 publications

(89 citation statements)

References 55 publications

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“…From spectroscopy with high signal-to-noise ratio of the 10 m Keck 1 telescope and HIRES echelle spectrograph, Schuler et al (2011) determined the abundance of 15 heavy elements in both stars and found them indistinguishable. On the other hand, Ramírez et al (2011) andTucci Maia et al (2014) claimed that 16 Cygni A is slightly more metal rich than 16 Cygni B based on spectra with high resolution Ramírez et al (2011); (c) Schuler et al (2011); White et al (2013), seismic determination; (e) White et al (2013), interferometric determination; ( f ) Tucci Maia et al (2014); (g) Metcalfe et al (2012); (h) Davies et al (2015); (i) King et al (1997); ( j) Deliyannis et al (2000); (k) Cochran et al (1997).…”

Section: Observational Constraintsmentioning

confidence: 99%

Accretion of planetary matter and the lithium problem in the 16 Cygni stellar system

Deal

Richard

Vauclair

2015

A&A

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Context. The 16 Cygni system is composed of two solar analogues with similar masses and ages. A red dwarf is in orbit around 16 Cygni A, and 16 Cygni B hosts a giant planet. The abundances of heavy elements are similar in the two stars, but lithium is much more depleted in 16 Cygni B than in 16 Cygni A, by a factor of at least 4.7. Aims. The interest of studying the 16 Cygni system is that the two star have the same age and the same initial composition. The differences currently observed must be due to their different evolution, related to the fact that one of them hosts a planet while the other does not. Methods. We computed models of the two stars that precisely fit the observed seismic frequencies. We used the Toulouse Geneva Evolution Code (TGEC), which includes complete atomic diffusion (including radiative accelerations). We compared the predicted surface abundances with the spectroscopic observations and confirm that another mixing process is needed. We then included the effect of accretion-induced fingering convection. Results. The accretion of planetary matter does not change the metal abundances but leads to lithium destruction, which depends upon the accreted mass. A fraction of the Earth's mass is enough to explain the lithium surface abundances of 16 Cygni B. We also checked the beryllium abundances. Conclusions. In the case of accretion of heavy matter onto stellar surfaces, the accreted heavy elements do not remain in the outer convective zones, but are mixed downwards by fingering convection induced by the unstable μ-gradient. Depending on the accreted mass, this mixing process may transport lithium down to its nuclear destruction layers and lead to an extra lithium depletion at the surface. A fraction of the Earth's mass is enough to explain a lithium ratio of 4.7 in the 16 Cygni system. In this case beryllium is not destroyed. Such a process may be frequent in planet-hosting stars and should be studied in other cases in the future.

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Section: Observational Constraintsmentioning

confidence: 99%

Accretion of planetary matter and the lithium problem in the 16 Cygni stellar system

Deal

Richard

Vauclair

2015

A&A

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“…Initial indications of anomalous rotation and magnetic activity in old field stars relied on asteroseismic properties from [21], which were based on an analysis of only 9 months of data ( [22]). Kepler completed its primary mission in 2013, but the large samples of multi-year observations posed an enormous data analysis challenge that has only recently been surmounted ( [23][24][25]). The longer data sets improved the signal-to-noise ratio (S/N) of the power spectrum for fainter stars with previously marginal detections, and yielded additional oscillation frequencies for the brighter targets.…”

Section: Asteroseismology With Keplermentioning

confidence: 99%

The impact of Gaia DR1 on asteroseismic inferences from Kepler

Metcalfe

Creevey

Saders³

2017

EPJ Web Conf.

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Abstract. The Kepler mission has been fantastic for asteroseismology of solar-type stars, but the targets are typically quite distant. As a consequence, the reliability of asteroseismic modeling has been limited by the precision of additional constraints from highresolution spectroscopy and parallax measurements. A precise luminosity is particularly useful to minimize potential biases due to the intrinsic correlation between stellar mass and initial helium abundance. We have applied the latest version of the Asteroseismic Modeling Portal (AMP) to the complete Kepler data sets for 30 stars with known rotation rates and chromospheric activity levels. We compare the stellar properties derived with and without the measured parallaxes from the first data release of Gaia. We find that in most cases the masses and ages inferred from asteroseismology shift within their uncertainties. For a few targets that show larger shifts, the updated stellar properties only strengthen previous conclusions about anomalous rotation in middle-aged stars. MotivationThe correlation between stellar mass and initial helium abundance is a long-standing problem in modeling solar-type stars. Increasing either the mass or the initial helium yields a model with a higher luminosity, so we can trade off one parameter for the other while still satisfying the observational constraints ([1]). Asteroseismic observations can reduce the severity of this problem by providing a strong constraint on the stellar radius, but the issue cannot be avoided entirely without a more direct constraint on the stellar luminosity. Without such a constraint, the correlation can lead to systematic biases in the stellar properties inferred from asteroseismology. In this paper, we examine the impact of including luminosity constraints derived from Gaia DR1 parallaxes ([2]) for a sample of 30 Kepler targets with known rotation rates ([3]) and chromospheric activity levels ([4]). Our goal is to evaluate the possibility of systematic biases in the asteroseismic masses and ages for stars with anomalous rotation compared to empirical gyrochronology relations ([5]), with implications for a new theory of magnetic evolution beyond middle age ([6]).Until recently, it was presumed that rotation and magnetism decay together throughout the lives of solar-type stars ([7, 8]). Although stars are formed with a range of initial rotation rates, the stellar winds entrained in their magnetic fields lead to angular momentum loss from magnetic braking. This forces convergence to a single rotation rate at a given mass after roughly 500 Myr. The Kepler mission allowed the measurement of rotation periods in old field stars whose masses and ages could be determined from asteroseismology. These new data revealed a population of field stars rotating

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“…due to rotation and the inclination angle i of the star (see, e. g., Chaplin et al 2013;Huber et al 2013b;Lund et al 2014;Davies et al 2015). Figure 5 shows the splitting versus inclination correlation map from the MCMC fit of EPIC 206009487.…”

Section: Seismic Parameter Estimationmentioning

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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Asteroseismic inference on rotation, gyrochronology and planetary system dynamics of 16 Cygni

Cited by 115 publications

References 55 publications

Accretion of planetary matter and the lithium problem in the 16 Cygni stellar system

Accretion of planetary matter and the lithium problem in the 16 Cygni stellar system

The impact of Gaia DR1 on asteroseismic inferences from Kepler

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

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