The dependence of convective core overshooting on stellar mass: reality check, and additional evidence. (arXiv:1904.02714v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Claret_A/0/1/0/all/0/1">Antonio Claret</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Torres_G/0/1/0/all/0/1">Guillermo Torres</a> (2) ((1) Inst. de Astrof. de Andalucia, and Dept. Fisica Teorica y del Cosmos, Univ. de Granada, Spain, (2) Center for Astrophysics | Harvard & Smithsonian, USA)
Overshooting from the convective cores of stars more massive than about 1.2
M(Sun) 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 (f[ov] 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 f[ov] on stellar mass, showing that it increases sharply up
to a mass of roughly 2 M(Sun), and remains constant thereafter out to at least
4.4 M(Sun). Recent claims have challenged the utility of eclipsing binaries for
this purpose, on the basis that the uncertainties in f[ov] 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 semi-empirical f[ov] determinations for 14
additional binaries to our previous sample, and to update the values for 8
others. All are consistent with, and strengthen our previous conclusions,
supporting a dependence of f[ov] on mass that is now based on estimates for a
total of 51 binary systems (102 stars).
Overshooting from the convective cores of stars more massive than about 1.2
M(Sun) 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 (f[ov] 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 f[ov] on stellar mass, showing that it increases sharply up
to a mass of roughly 2 M(Sun), and remains constant thereafter out to at least
4.4 M(Sun). Recent claims have challenged the utility of eclipsing binaries for
this purpose, on the basis that the uncertainties in f[ov] 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 semi-empirical f[ov] determinations for 14
additional binaries to our previous sample, and to update the values for 8
others. All are consistent with, and strengthen our previous conclusions,
supporting a dependence of f[ov] on mass that is now based on estimates for a
total of 51 binary systems (102 stars).
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