Context. Numerous spectroscopic observations provide compelling evidence for non-canonical processes that modify the surface abundances of low-and intermediate-mass stars beyond the predictions of standard stellar theory. Aims. We study the effects of thermohaline instability and rotation-induced mixing in the 1-4 M range at solar metallicity. Methods. We present evolutionary models by considering both thermohaline and rotation-induced mixing in stellar interior. We discuss the effects of these processes on the chemical properties of stars from the zero age main sequence up to the end of the second dredge-up on the early-AGB for intermediate-mass stars and up to the AGB tip for low-mass stars. Model predictions are compared to observational data for lithium, 12 Results. Thermohaline mixing simultaneously accounts for the observed behaviour of 12 C/ 13 C, [N/C], and lithium in low-mass stars that are more luminous than the RGB bump, and its efficiency is increasing with decreasing initial stellar mass. On the TP-AGB, thermohaline mixing leads to lithium production, although the 7 Li yields remain negative. Although the 3 He stellar yields are much reduced thanks to this process, we find that solar-metallicity, low-mass stars remain net 3 He producers. Rotation-induced mixing is found to change the stellar structure so that in the mass range between ∼1.5 and 2.2 M the thermohaline instability occurs earlier on the red giant branch than in non-rotating models. Finally rotation accounts for the observed star-to-star abundance variations at a given evolutionary status, and is necessary to explain the features of CN-processed material in intermediate-mass stars. Conclusions. Overall, the present models account for the observational constraints very well over the whole mass range presently investigated.
Context. The availability of asteroseismic constraints for a large sample of stars from the missions CoRoT and Kepler paves the way for various statistical studies of the seismic properties of stellar populations. Aims. We evaluate the impact of rotation-induced mixing and thermohaline instability on the global asteroseismic parameters at different stages of the stellar evolution from the zero age main sequence to the thermally pulsating asymptotic giant branch to distinguish stellar populations. Methods. We present a grid of stellar evolutionary models for four metallicities (Z = 0.0001, 0.002, 0.004, and 0.014) in the mass range from 0.85 to 6.0 M . The models are computed either with standard prescriptions or including both thermohaline convection and rotation-induced mixing. For the whole grid, we provide the usual stellar parameters (luminosity, effective temperature, lifetimes, ... ), together with the global seismic parameters, i.e. the large frequency separation and asymptotic relations, the frequency corresponding to the maximum oscillation power ν max , the maximal amplitude A max , the asymptotic period spacing of g-modes, and different acoustic radii. Results. We discuss a signature of rotation-induced mixing on the global asteroseismic quantities, that can be detected observationally. Thermohaline mixing whose effects can be identified using spectroscopic studies cannot be characterized by the global seismic parameters studied here. However, we cannot exclude that individual mode frequencies or other well chosen asteroseismic quantities might help us to constrain this mixing.
Context. The detection of oscillations with a mixed character in subgiants and red giants allows us to probe the physical conditions in their cores. Aims. With these mixed modes, we aim at determining seismic markers of stellar evolution. Methods. Kepler asteroseismic data were selected to map various evolutionary stages and stellar masses. Seismic evolutionary tracks were then drawn with the combination of the frequency and period spacings. Results. We measured the asymptotic period spacing for 1178 stars at various evolutionary stages. This allows us to monitor stellar evolution from the main sequence to the asymptotic giant branch and draw seismic evolutionary tracks. We present clear quantified asteroseismic definitions that characterize the change in the evolutionary stages, in particular the transition from the subgiant stage to the early red giant branch, and the end of the horizontal branch. Conclusions. The seismic information is so precise that clear conclusions can be drawn independently of evolution models. The quantitative seismic information can now be used for stellar modeling, especially for studying the energy transport in the heliumburning core or for specifying the inner properties of stars entering the red or asymptotic giant branches. Modeling will also allow us to study stars that are identified to be in the helium-subflash stage, high-mass stars either arriving or quitting the secondary clump, or stars that could be in the blue-loop stage.
Aims. We present an extended grid of state-of-the art stellar models for low-mass stars including updated physics (nuclear reaction rates, surface boundary condition, mass-loss rate, angular momentum transport, torque and rotation-induced mixing prescriptions). We aim at evaluating the impact of wind braking, realistic atmospheric treatment, rotation and rotation-induced mixing on the structural and rotational evolution from the pre-main sequence to the turn-off. Methods. Using the STAREVOL code, we provide an updated PMS grid. We compute stellar models for 7 different metallicities, from [Fe/H] = -1 dex to [Fe/H] = +0.3 dex with a solar composition corresponding to Z = 0.0134. The initial stellar mass ranges from 0.2 to 1.5 M with extra grid refinement around one solar mass. We also provide rotating models for three different initial rotation rates (slow, median and fast) with prescriptions for the wind braking and disc-coupling timescale calibrated on observed properties of young open clusters. The rotational mixing includes an up-to-date description of the turbulence anisotropy in stably stratified regions. Results. The overall behaviour of our models at solar metallicity -and its constitutive physics -is validated through a detailed comparison with a variety of distributed evolutionary tracks. The main differences arise from the choice of surface boundary conditions and initial solar composition. The models including rotation with our prescription for angular momentum extraction and self-consistent formalism for angular momentum transport are able to reproduce the rotation period distribution observed in young open clusters over a broad mass-range. These models are publicly available and may be used to analyse data coming from present and forthcoming asteroseismic and spectroscopic surveys such as Gaia, TESS and PLATO.
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