New light on the driving mechanism in roAp stars. Part I. Effects of metallicity

Abstract

Observations suggest that a relationship exists between the driving mechanism of roAp star pulsations and the heavy element distribution in these stars. We attempt to study the effects of local and global metallicity variations on the excitation mechanism of high order p-modes in A star models. We developed stellar evolutionary models to describe magnetic A stars with different global metallicity or local metal accumulation profiles. These models were computed with CLES ("Code Liègeois d'évolution stellaire"), and the stability of our models was assessed with the non-adiabatic oscillation code MAD. Our models reproduce the blue edge of the roAp star instability strip, but generate a red edge hotter than the observed one, regardless of metallicity. Surprisingly, we find that an increase in opacity inside the driving region can produce a lower amount of driving, which we refer to as the "inverse $\kappa$-mechanism".

arXiv comment18 pages, 23 figures. Accepted for publication in A&A

References in corpus (6)

• Low Temperature Opacities
• New measurements of magnetic fields of roAp stars with FORS1 at the VLT
• How to drive roAp stars
• Radial Velocity Variations in Pulsating Ap Stars III. The Discovery of 16.21 min Oscillations in Beta CrB
• HD 178892 - a cool Ap star with extremely strong magnetic field
• Theory of rapidly oscillating Ap stars

Cited by in corpus (6)

• Kepler observations of a roAp star: delta Scuti and gamma Doradus pulsations in Ap stars
• The first evidence for multiple pulsation axes: a new roAp star in the Kepler field, KIC 10195926
• Testing excitation models of rapidly oscillating Ap stars with interferometry
• Discovery of new roAp pulsators in the UVES survey of cool magnetic Ap stars
• Time-resolved photometric and spectroscopic analysis of a luminous Ap star HD103498
• Time resolved spectroscopy of the cool Ap star HD 213637