[en] Context: Observations suggest that a relationship exists between the driving mechanism of roAp star pulsations and the heavy element distribution in these stars. Aims: 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. Methods: 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. Results: 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''.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Théado, S.; Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 14 avenue Edouard Belin, 31400 Toulouse, France ; Institut d'Astrophysique et de Géophysique de Liège, Allé du 6 Août 17, 4000 Liège, Belgium
Dupret, Marc-Antoine ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique
Noels-Grötsch, Arlette ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO)
Ferguson, J. W.; Department of Physics, Wichita State University, Wichita, KS 67260-0032, USA
Language :
English
Title :
New light on the driving mechanism in roAp stars. I. Effects of metallicity
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