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g-mode trapping and period spacings in hot B subdwarf stars

Published online by Cambridge University Press:  18 February 2014

S. Charpinet
Affiliation:
Université de Toulouse, UPS-OMP, IRAP, Toulouse, France email: [email protected] CNRS, IRAP, 14 avenue Edouard Belin, 31400 Toulouse, France
V. Van Grootel
Affiliation:
Institut d'Astrophysique et de Géophysique de l'Université de Liège, Allée du 6 Août 17, B-4000 Liège, Belgium
P. Brassard
Affiliation:
Université de Montréal, Pavillon Roger-Gaudry, Département de Physique, CP 6128, Succ. Centre-Ville, Montréal QC, H3C 3J7, Canada
G. Fontaine
Affiliation:
Université de Montréal, Pavillon Roger-Gaudry, Département de Physique, CP 6128, Succ. Centre-Ville, Montréal QC, H3C 3J7, Canada
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Abstract

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Hot B subdwarfs (sdB) are hot and compact helium core burning stars of nearly half a solar mass that can develop pulsational instabilities driving acoustic and/or gravity modes. These evolved stars are expected to be chemically stratified with an almost pure hydrogen envelope surrounding a helium mantle on top of a carbon/oxygen enriched core. However, the sdB stars pulsating in g-modes show regularities in their observed period distributions that, surprisingly (at first sight), are typical of the behavior of high order g-modes in chemically homogeneous (i.e., non-stratified) stars. This led to a claim that hot B subdwarfs could be much less chemically stratified than previously thought. Here, we reinvestigate trapping effects affecting g-modes in sdB stars. We show that standard stratified models of such stars can also produce nearly constant period spacings in the low frequency range similar to those found in g-mode spectra of sdB stars monitored with Kepler.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2014 

References

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