<i>Kepler</i>observations of the asteroseismic binary HD 176465

White, T. R.; Benomar, O.; Aguirre, V. Silva; Ball, Warrick H.; Bedding, Timothy R.; Chaplin, W. J.; Christensen‐Dalsgaard, J.; García, R. A.; Gizon, Laurent; Stello, Dennis; Aigrain, S.; Antia, H. M.; Appourchaux, T.; Bazot, M.; Campante, Tiago L.; Creevey, O.; Davies, G. R.; Elsworth, Y.; Gaulme, P.; Handberg, R.; Hekker, S.; Houdek, G.; Howe, R.; Huber, Daniel; Karoff, C.; Marques, J. P.; Mathur, S.; McQuillan, A.; Metcalfe, T. S.; Mosser, B.; Nielsen, M. B.; Régulo, C.; Salabert, D.; Stahn, T.

doi:10.1051/0004-6361/201628706

Cited by 36 publications

(35 citation statements)

References 113 publications

(126 reference statements)

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“…The shaded region represents the expected dispersion due to the range of masses and metallicities within the sample (e.g., the two high points are lower metallicity stars, giving them thinner convection zones that reach the critical Rossby number at faster rotation rates). The asteroseismic rotation rates and ages for a ∼3 Gyr-old solar analog binary system (White et al, 2017) have been overplotted, validating asteroseismic rotation measurements and the age scale for sun-like Kepler stars. A few well-characterized solar analogs are shown with yellow points, including 18 Sco (Petit et al, 2008;Li et al, 2012;Mittag et al, 2016), α Cen A (Bazot et al, 2007;Bazot, Bourguignon, and ChristensenDalsgaard, 2012), and 16 Cyg A & B Creevey et al, 2017).…”

Section: Breakdown Of Magnetic Brakingmentioning

confidence: 54%

Magnetic Evolution and the Disappearance of Sun-Like Activity Cycles

Metcalfe

Saders

2017

Sol Phys

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After decades of effort, the solar activity cycle is exceptionally well characterized but it remains poorly understood. Pioneering work at the Mount Wilson Observatory demonstrated that other sun-like stars also show regular activity cycles, and suggested two possible relationships between the rotation rate and the length of the cycle. Neither of these relationships correctly describe the properties of the Sun, a peculiarity that demands explanation. Recent discoveries have started to shed light on this issue, suggesting that the Sun's rotation rate and magnetic field are currently in a transitional phase that occurs in all middleaged stars. Motivated by these developments, we identify the manifestation of this magnetic transition in the best available data on stellar cycles. We propose a reinterpretation of previously published observations to suggest that the solar cycle may be growing longer on stellar evolutionary timescales, and that the cycle might disappear sometime in the next 0.8-2.4 Gyr. Future tests of this hypothesis will come from ground-based activity monitoring of Kepler targets that span the magnetic transition, and from asteroseismology with the TESS mission to determine precise masses and ages for bright stars with known cycles.

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Section: Breakdown Of Magnetic Brakingmentioning

confidence: 54%

Magnetic Evolution and the Disappearance of Sun-Like Activity Cycles

Metcalfe

Saders

2017

Sol Phys

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“…In another, study soon to appear, Themeßl et al (2017) present a reanalysis of KIC 8410637 from the full 4 years of Kepler photometry and extended spectroscopic monitoring and present a detailed analysis of KIC 6540750 and KIC 9540226. On the main sequence, several binary stars have been analysed, such as KIC 7510397 (Appourchaux et al 2015), KIC 10124866 (White et al 2017) or the system of 16 Cyg A&B (Metcalfe et al 2015;Davies et al 2015) in which both components are oscillating. The red-giant or sub-giant primaries of only few binary systems, Procyon, θ 1 Tau, µ Herculi, were studied with seismology through the groundbased observations, utilising high-resolution spectroscopy with a meter-per-second accuracy (Arentoft et al 2008;Beck et al 2015b;Grundahl et al 2017, respectively).…”

Section: Introductionmentioning

confidence: 99%

Seismic probing of the first dredge-up event through the eccentric red-giant and red-giant spectroscopic binary KIC 9163796

Beck

Kallinger

Pavlovski

et al. 2018

A&A

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Context. Binaries in double-lined spectroscopic systems (SB2) provide a homogeneous set of stars. Differences of parameters, such as age or initial conditions, which otherwise would have strong impact on the stellar evolution, can be neglected. The observed differences are determined by the difference in stellar mass between the two components. The mass ratio can be determined with much higher accuracy than the actual stellar mass. Aims. In this work, we aim to study the eccentric binary system KIC 9163796, whose two components are very close in mass and both are low-luminosity red-giant stars. Methods. We analyse four years of Kepler space photometry and we obtained high-resolution spectroscopy with the Hermes instrument. The orbital elements and the spectra of both components were determined using spectral disentangling methods. The effective temperatures, and metallicities were extracted from disentangled spectra of the two stars. Mass and radius of the primary were determined through asteroseismology. The surface rotation period of the primary is determined from the Kepler light curve. From representative theoretical models of the star, we derived the internal rotational gradient, while for a grid of models, the measured lithium abundance is compared with theoretical predictions. Results. From seismology the primary of KIC 9163796 is a star of 1.39±0.06 M ⊙ , while the spectroscopic mass ratio between both components can be determined with much higher precision by spectral disentangling to be 1.015±0.005. With such mass and a difference in effective temperature of 600 K from spectroscopy, the secondary and primary are, respectively, in the early and advanced stage of the first dredge-up event on the red-giant branch. The period of the primary's surface rotation resembles the orbital period within 10 days.The radial rotational gradient between the surface and core in KIC 9163796 is found to be 6.9 +2.0 −1.0 . This is a low value but not exceptional if compared to the sample of typical single field stars. The seismic average of the envelope's rotation agrees with the surface rotation rate. The lithium abundance is in agreement with quasi rigidly-rotating models. Conclusions. The agreement between the surface rotation with the seismic result indicates that the full convective envelope is rotating quasi-rigidly. The models of the lithium abundance are compatible with a rigid rotation in the radiative zone during the main sequence. Because of the many constraints offered by oscillating stars in binary systems, such objects are important test beds of stellar evolution.

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“…Hjørringgaard et al (2017) have reported on discrepancies between constraints from different independent methods when determining the parameters of the very well-studied red giant HD 185351. Moreover, the problem of an unconstrained α MLT is not unique to red giants: White et al (2017) showed that their parameter determinations using changed significantly when α MLT was free to vary compared to a fixed solar value.…”

Section: Introductionmentioning

confidence: 99%

Stellar models with calibrated convection and temperature stratification from 3D hydrodynamics simulations

Mosumgaard

Ball

Aguirre

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Stellar evolution codes play a major role in present-day astrophysics, yet they share common simplifications related to the outer layers of stars. We seek to improve on this by the use of results from realistic and highly detailed 3D hydrodynamics simulations of stellar convection. We implement a temperature stratification extracted directly from the 3D simulations into two stellar evolution codes to replace the simplified atmosphere normally used. Our implementation also contains a non-constant mixing-length parameter, which varies as a function of the stellar surface gravity and temperature -also derived from the 3D simulations. We give a detailed account of our fully consistent implementation and compare to earlier works, and also provide a freely available -module. The evolution of low-mass stars with different masses is investigated, and we present for the first time an asteroseismic analysis of a standard solar model utilising calibrated convection and temperature stratification from 3D simulations. We show that the inclusion of 3D results have an almost insignificant impact on the evolution and structure of stellar models -the largest effect are changes in effective temperature of order 30 K seen in the pre-main sequence and in the red-giant branch. However, this work provides the first step for producing self-consistent evolutionary calculations using fully incorporated 3D atmospheres from on-the-fly interpolation in grids of simulations.

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Keplerobservations of the asteroseismic binary HD 176465

Cited by 36 publications

References 113 publications

Magnetic Evolution and the Disappearance of Sun-Like Activity Cycles

Magnetic Evolution and the Disappearance of Sun-Like Activity Cycles

Seismic probing of the first dredge-up event through the eccentric red-giant and red-giant spectroscopic binary KIC 9163796

Stellar models with calibrated convection and temperature stratification from 3D hydrodynamics simulations

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