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Context. The theory of rotational and chemical evolution is incomplete, thereby limiting the accuracy of model-dependent stellar mass and age determinations. The γ Doradus (γ Dor) pulsators are excellent points of calibration for the current state-of-the-art stellar evolution models, as their gravity modes probe the physical conditions in the deep stellar interior. Yet, individual asteroseismic modelling of these stars is not always possible because of insufficient observed oscillation modes. Aims. This paper presents a novel method to derive distributions of the stellar mass, age, core-boundary mixing efficiency, and initial rotation rates for γ Dor stars. Methods. We computed a grid of rotating stellar evolution models covering the entire γ Dor instability strip. We then used the observed distributions of the luminosity, effective temperature, buoyancy travel time, and near-core rotation frequency of a sample of 539 stars to assign a statistical weight to each of our models. This weight is a measure of how likely the combination of a specific model is. We then computed weighted histograms to derive the most likely distributions of the fundamental stellar properties. Results. We find that the rotation frequency at zero-age main sequence follows a normal distribution, peaking at around 25% of the critical Keplerian rotation frequency. The probability-density function for extent of the core-boundary mixing zone, given by a factor of fCBM times the local pressure scale height (assuming an exponentially decaying parameterisation), decreases linearly with increasing fCBM. Conclusions. Converting the distribution of fractions of critical rotation at the zero-age main sequence to units of d−1, we find most F-type stars start the main sequence with a rotation frequency between 0.5 d−1 and 2 d−1. Regarding the core-boundary mixing efficiency, we find that it is generally weak in this mass regime. [ABSTRACT FROM AUTHOR]

Contact. Rotation is a key ingredient in the theory of stellar structure and evolution. Until now, stellar evolution codes operate in a one-dimensional framework for which the validity domain in regards to the rotation rate is not well understood. Aims. In this Letter, we present the first results of self-consistent stellar models in two spatial dimensions, which compute the time evolution of a star and its rotation rate along the main sequence (MS). We also present a comparison to observations. Methods. We make use of an extended version of the ESTER code, which solves the stellar structure of a rotating star in two dimensions with time evolution, including chemical evolution, and an implementation of rotational mixing. We computed evolution tracks for a 12 M⊙ model, once for an initial rotation rate equal to 15% of the critical frequency, and once for 50%. Results. We first show that our model initially rotating at 15% of the critical frequency is able to reproduce all the observations of the β Cephei star HD 192575, which was recently studied with asteroseismology. Beyond the classical surface parameters, such as effective temperature or luminosity, our model also reproduces the core mass along with the rotation rate of the core and envelope at the estimated age of the star. This particular model also shows that the meridional circulation has a negligible influence on the transport of chemical elements such as nitrogen, for which the abundance may be increased at the stellar surface. Furthermore, it shows that in the late MS, nuclear evolution is faster than the relaxation time needed to reach a steady state of stellar angular momentum distribution. Conclusions. We demonstrate that we have successfully taken a new step towards two-dimensional evolutionary modelling of rotating stars. This opens new perspectives on the understanding of the dynamics of fast rotating stars and on the way rotation impacts stellar evolution. [ABSTRACT FROM AUTHOR]

Context. The physical mechanisms driving the transport of angular momentum in stars are not fully understood, as current models cannot explain the observed stellar rotation profiles across all stages of evolution. Aims. By making use of pulsating F-type dwarfs, we aim to (i) observationally calibrate the efficiency of angular momentum transport, assuming a constant uniform viscosity, and (ii) test how well state-of-the-art rotating stellar models with angular momentum (AM) transport by rotationally induced processes can explain observed rotation profiles. In both cases, the aim is to simultaneously reproduce the measured near-core rotation and core-to-surface rotation ratio. Methods. Asteroseismic modelling is applied to a sample of seven slowly rotating pulsators in order to derive (core) masses and ages from their gravity-mode oscillations. This work focuses on the main sequence (MS), using models that start with an initial uniform rotation frequency at the start of core-hydrogen burning, which is a free parameter. Two treatments of AM transport are considered: (i) a constant uniform viscosity, and (ii) rotationally induced processes (including the Spruit-Tayler dynamo). Next, the initial rotation frequency of each star is derived from the observed present-day near-core rotation frequency for both treatments. Results. Asteroseismic modelling of gravity mode periods reveals that all seven slowly rotating stars (one of which is not further modelled) in the sample are near the end of core-hydrogen burning. To explain the near-core rotation rate at the inferred age, initial rotation frequencies at the zero-age main sequence need to be below 10% of the initial critical break-up frequency. The derived initial rotation frequencies are consistent with previous works. Conclusions. A diffusive approximation of angular momentum transport can in general explain the observed rotation profiles of the six slowly rotating F-type dwarfs for average values of the viscosity of between 2 × 105 and 5 × 107 cm2 s−1 or when the viscosity is computed from rotationally induced mechanisms. Yet, for three stars in the sample, the core-to-surface rotation fraction from rotationally induced mechanisms is predicted to be higher than observed. [ABSTRACT FROM AUTHOR]

Context. Asteroseismic studies show that cores of post-main-sequence stars rotate more slowly than theoretically predicted by stellar models with purely hydrodynamical transport processes. Recent studies of main-sequence stars, particularly Gamma Doradus (γ Dor) stars, have revealed the internal rotation rates for hundreds of stars, offering a counterpart on the main sequence for studies of angular momentum transport. Aims. We investigate whether such a disagreement between observed and predicted internal rotation rates is present in main-sequence stars by studying angular momentum transport in γ Dor stars. Furthermore, we test whether models of rotating stars with internal magnetic fields can reproduce their rotational properties. Methods. We computed rotating models with the Geneva stellar evolution code taking into account meridional circulation and shear instability. We also computed models with internal magnetic fields using a general formalism for transport by the Tayler-Spruit dynamo. We then compared these models to observational constraints for γ Dor stars that we compiled from the literature, thus combining the core rotation rates, projected rotational velocities from spectroscopy, and constraints on their fundamental parameters. Results. We show that combining the different observational constraints available for γ Dor stars enable us to clearly distinguish the different scenarios for internal angular momentum transport. Stellar models with purely hydrodynamical processes are in disagreement with the data, whereas models with internal magnetic fields can reproduce both core and surface constraints simultaneously. Conclusions. Similarly to results obtained for subgiant and red giant stars, angular momentum transport in radiative regions of γ Dor stars is highly efficient, in good agreement with predictions of models with internal magnetic fields. [ABSTRACT FROM AUTHOR]

The asteroseismic modelling of period spacing patterns from gravito-inertial modes in stars with a convective core is a high-dimensional problem. We utilize the measured period spacing pattern of prograde dipole gravity modes (acquiring Π0), in combination with the effective temperature (T eff) and surface gravity (log  g) derived from spectroscopy, to estimate the fundamental stellar parameters and core properties of 37 γ Doradus (γ Dor) stars whose rotation frequency has been derived from Kepler photometry. We use two 6D grids of stellar models, one with step core overshooting and another with exponential core overshooting, to evaluate correlations between the three observables Π0, T eff, and log  g and the mass, age, core overshooting, metallicity, initial hydrogen mass fraction, and envelope mixing. We provide multivariate linear model recipes relating the stellar parameters to be estimated to the three observables (Π0, T eff, log  g). We estimate the (core) mass, age, core overshooting, and metallicity of γ Dor stars from an ensemble analysis and achieve relative uncertainties of ∼10 per cent for the parameters. The asteroseismic age determination allows us to conclude that efficient angular momentum transport occurs already early on during the main sequence. We find that the nine stars with observed Rossby modes occur across almost the entire main-sequence phase, except close to core-hydrogen exhaustion. Future improvements of our work will come from the inclusion of more types of detected modes per star, larger samples, and modelling of individual mode frequencies. [ABSTRACT FROM AUTHOR]