CoRoT Symposium 3, Kepler KASC-7 joint meeting
6-11 Jul 2014 Toulouse (France)

Abstracts > Sonoi Takafumi

Nonadiabatic analysis of strange-modes in hot massive stars with time-dependent convection
Takafumi Sonoi  1@  , Hiromoto Shibahashi  2, *@  
1 : Laboratoire d'études spatiales et d'instrumentation en astrophysique  (LESIA)  -  Website
Université Pierre et Marie Curie [UPMC] - Paris VI, Observatoire de Paris, INSU, CNRS : UMR8109, Université Paris VII - Paris Diderot, Université Pierre et Marie Curie (UPMC) - Paris VI
5, place Jules Janssen 92190 MEUDON -  France
2 : University of Tokyo, Department of Astronomy  -  Website
Hongo 7-3-1, Bunkyo-ku, Tokyo, 113-0033 -  Japan
* : Corresponding author

Strange-modes have been so far investigated mainly in theory. They appear high luminosity star models with $L/M>10^4L_\odot/M_\odot$ such as massive stars, Wolf-Rayet stars, helium stars, etc. In CoRoT observations, light variations of a B-type supergiant HD50064 were found. After that, Aerts et al. (2010) carried out a follow-up observation to the star. They suggested that the variations the star shows could be caused by a strange-mode oscillation. In addition, they found that the mass-loss rate is changing in a timescale similar to changes in the photometric and spectroscopic variability. Recently, nonlinear calculations have been performed to explain associations between mass-loss and strange-mode oscillations. So far strange-modes have been analyzed by the frozen-in convection approximation. In massive stars, however, the Fe opacity bump induces convection with a certain contribution of convective luminosity. Therefore, we cannot definitely conclude that convection never affects oscillations. We carry out a nonadiabatic analysis with time-dependent convection in hot massive stars. We found that modes excited at the Fe bump are damped by convection. On the other hand, convection hardly damps ones excited around the He bump because of negligible contribution of convective luminosity in the He bump convection zone. In whole, instability of strange-modes is weaken by convection, but it still remains in hot massive stars.

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