Probability distributions of initial rotation velocities and coreboundary mixing efficiencies of γ Doradus stars
Abstract
Context. The theory of rotational and chemical evolution is incomplete, thereby limiting the accuracy of modeldependent stellar mass and age determinations. The γ Doradus (γ Dor) pulsators are excellent points of calibration for the current stateoftheart 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, coreboundary 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 nearcore 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 zeroage main sequence follows a normal distribution, peaking at around 25% of the critical Keplerian rotation frequency. The probabilitydensity function for extent of the coreboundary mixing zone, given by a factor of f_{CBM} times the local pressure scale height (assuming an exponentially decaying parameterisation), decreases linearly with increasing f_{CBM}.
Conclusions: Converting the distribution of fractions of critical rotation at the zeroage main sequence to units of d^{−1}, we find most Ftype stars start the main sequence with a rotation frequency between 0.5 d^{−1} and 2 d^{−1}. Regarding the coreboundary mixing efficiency, we find that it is generally weak in this mass regime.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 May 2024
 DOI:
 10.1051/00046361/202449213
 arXiv:
 arXiv:2402.05171
 Bibcode:
 2024A&A...685A..21M
 Keywords:

 asteroseismology;
 stars: evolution;
 stars: interiors;
 stars: oscillations;
 stars: rotation;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 Accepted for publication in Astronomy &