Abstract
Context. In asteroseismology an important diagnostic of the evolutionary
status of a star is the small frequency separation which is sensitive to
the gradient of the mean molecular weight in the stellar interior. It is
thus interesting to discuss the classical age-activity relations in
terms of this quantity. Moreover, as the photospheric magnetic field
tends to suppress the amplitudes of acoustic oscillations, it is
important to quantify the importance of this effect by considering
various activity indicators. Aims: We propose a new class of
age-activity relations that connects the Mt. Wilson S index and the
average scatter in the light curve with the small frequency separation
and the amplitude of the p-mode oscillations. Methods: We used a
Bayesian inference to compute the posterior probability of various
empirical laws for a sample of 19 solar-like active stars observed by
the Kepler telescope. Results: We demonstrate the presence of a
clear correlation between the Mt. Wilson S index and the relative age of
the stars as indicated by the small frequency separation, as well as an
anti-correlation between the S index and the oscillation amplitudes. We
argue that the average activity level of the stars shows a stronger
correlation with the small frequency separation than with the absolute
age that is often considered in the literature. Conclusions: The
phenomenological laws discovered in this paper have the potential to
become new important diagnostics to link stellar evolution theory with
the dynamics of global magnetic fields. In particular we argue that the
relation between the Mt. Wilson S index and the oscillation amplitudes
is in good agreement with the findings of direct numerical simulations
of magneto-convection.
| Originalsprog | Engelsk |
|---|---|
| Artikelnummer | A35 |
| Tidsskrift | Astronomy & Astrophysics |
| Vol/bind | 571 |
| Antal sider | 5 |
| ISSN | 0004-6361 |
| DOI | |
| Status | Udgivet - 1 nov. 2014 |