[en] 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.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Charpinet, Stéphane
Van Grootel, Valérie ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Brassard, Pierre
Fontaine, Gilles
Language :
English
Title :
G-mode trapping and period spacings in hot B subdwarf stars
Publication date :
February 2014
Event name :
IAU Symposium 301: Precision Asteroseismology
Event organizer :
J. Daszynska-Daszkiewicz
Event place :
Wroclaw, Poland
Event date :
19-23 août 2013
Audience :
International
Journal title :
Proceedings of the International Astronomical Union