Can mass loss and overshooting prevent the excitation of g-modes in blue supergiants?

Mélanie Godart (1) , Arlette Noels (1) , Marc-Antoine Dupret (2) , Yveline Lebreton (3)

1 Département des Sciences et Gestion de l'Environnement/Océanologie [Liège]
2 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
3 SIMPA

Thanks to their past history on the main-sequence phase, supergiant massive stars develop a convective shell around the helium core. This intermediate convective zone (ICZ) plays an essential role in governing which g-modes are excited. Indeed, a strong radiative damping occurs in the high-density radiative core but the ICZ acts as a barrier preventing the propagation of some g-modes into the core. These g-modes can thus be excited in supergiant stars by the κ-mechanism in the superficial layers due to the opacity bump of iron, at logT = 5.2. However, massive stars are submitted to various complex phenomena such as rotation, magnetic fields, semiconvection, mass loss, overshooting. Each of these phenomena exerts a significant effect on the evolution and some of them could prevent the onset of the convective zone. We develop a numerical method which allows us to select the reflected, thus the potentially excited, modes only. We study different cases in order to show that mass loss and overshooting, in a large enough amount, reduce the extent of the ICZ and are unfavourable to the excitation of g-modes.

Mots clés: stars: evolution; stars: mass-loss; stars: oscillations; supergiants; stars; evolution -stars; mass-loss -stars; oscillations -supergiants

Domaines: Astrophysique stellaire et solaire [astro-ph.SR]; Astrophysique stellaire et solaire [astro-ph.SR]

Mélanie Godart, Arlette Noels, Marc-Antoine Dupret, Yveline Lebreton. Can mass loss and overshooting prevent the excitation of g-modes in blue supergiants?. Monthly Notices of the Royal Astronomical Society, 2009, 396 (4), pp.1833-1841. ⟨10.1111/J.1365-2966.2009.14903.X⟩. ⟨hal-00667369⟩