The dependence of convective core overshooting on stellar mass: reality check and additional evidence.
CLARET A. and TORRES G.
Abstract (from CDS):
Overshooting from the convective cores of stars more massive than about 1.2 M☉ has a profound impact on their subsequent evolution. And yet, the formulation of the overshooting mechanism in current stellar evolution models has a free parameter (fov in the diffusive approximation) that remains poorly constrained by observations, affecting the determination of astrophysically important quantities such as stellar ages. In an earlier series of papers, we assembled a sample of 37 well-measured detached eclipsing binaries to calibrate the dependence of fov on stellar mass, showing that it increases sharply up to a mass of roughly 2 M☉, and remains constant thereafter out to at least 4.4 M☉. Recent claims have challenged the utility of eclipsing binaries for this purpose, on the basis that the uncertainties in fov from the model fits are typically too large to be useful, casting doubt on a dependence of overshooting on mass. Here we reexamine those claims and show them to be too pessimistic, mainly because they did not account for all available constraints-both observational and theoretical-in assessing the true uncertainties. We also take the opportunity to add semiempirical fov determinations for 13 additional binaries to our previous sample, and to update the values for 9 others. All are consistent with and strengthen our previous conclusions, supporting a dependence of fov on mass that is now based on estimates for a total of 50 binary systems (100 stars).