Reference : Testing the effects of opacity and the chemical mixture on the excitation of pulsations ...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
http://hdl.handle.net/2268/123232
Testing the effects of opacity and the chemical mixture on the excitation of pulsations in B stars of the Magellanic Clouds
English
Salmon, Sébastien mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie >]
Montalban Iglesias, Josefa [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie >]
Morel, Thierry [Université de Liège - ULg > > GAPHE : Astrophysique observationnelle (sol et espace) >]
Miglio, Andrea [University of Birmingham > > > >]
Dupret, Marc-Antoine [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie >]
Noels-Grötsch, Arlette [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO) >]
Jun-2012
Monthly Notices of the Royal Astronomical Society
Blackwell Publishing
422
3460–3474
Yes (verified by ORBi)
International
0035-8711
Oxford
United Kingdom
[en] opacity ; stars: abundances ; stars: early-type ; stars: oscillations ; stars: variables: general ; Magellanic Clouds
[en] The B-type pulsators known as β Cephei and slowly pulsating B (SPB) stars present pulsations driven by the κ mechanism, which operates thanks to an opacity bump due to the iron-group elements. In low-metallicity environments such as the Magellanic Clouds, β Cep and SPB pulsations are not expected. Nevertheless, recent observations show evidence for the presence of B-type pulsator candidates in both galaxies.

We seek an explanation for the excitation of β Cep and SPB modes in those galaxies by examining basic input physics in stellar modelling: (i) the specific metal mixture of B-type stars in the Magellanic Clouds and (ii) the role of a potential underestimation of stellar opacities.

We first derive the present-day chemical mixtures of B-type stars in the Magellanic Clouds. Then, we compute stellar models for that metal mixture and perform a non-adiabatic analysis of these models. In the second approach, we simulate parametric enhancements of stellar opacities due to different iron-group elements. We then study their effects in models of B stars and their stability.

We find that adopting a representative chemical mixture of B stars in the Small Magellanic Cloud cannot explain the presence of B-type pulsators there. An increase of the opacity in the region of the iron-group bump could drive B-type pulsations, but only if this increase occurs at the temperature corresponding to the maximum contribution of Ni to this opacity bump. We recommend an accurate computation of the Ni opacity to understand B-type pulsators in the Small Magellanic Cloud, as well as the frequency domain observed in some Galactic hybrid β Cep–SPB stars.
Fonds pour la formation à la Recherche dans l'Industrie et dans l'Agriculture (Communauté française de Belgique) - FRIA
Researchers ; Students
http://hdl.handle.net/2268/123232
10.1111/j.1365-2966.2012.20857.x
The definitive version is available at www3.interscience.wiley.com

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