3D simulations of Betelgeuse's bow shock

作者：Mohamed S^*; Mackey J; Langer N

来源：Astronomy & Astrophysics, 2012, 541: A1.

DOI：10.1051/0004-6361/201118002

• hydrodynamics
• instabilities
• circumstellar matter
• stars: winds, outflows
• supergiants
• ISM: structure

Betelgeuse, the bright, cool red supergiant in Orion, is moving supersonically relative to the local interstellar medium. The star emits a powerful stellar wind that collides with this medium, forming a cometary structure, a bow shock, pointing in the direction of motion. We present the first 3D hydrodynamic simulations of the formation and evolution of Betelgeuse's bow shock. The models include realistic low-temperature cooling and cover a range of plausible interstellar medium densities of 0.3-1.9 cm(-3) and stellar velocities of 28-73 km s(-1). We show that the flow dynamics and morphology of the bow shock differ substantially because of the growth of Rayleigh-Taylor or Kelvin-Helmholtz instabilities. The former dominate the models with slow stellar velocities resulting in a clumpy bow shock substructure, whereas the latter produce a smoother, more layered substructure in the fast models. If the mass in the bow shock shell is low, as seems to be implied by the AKARI luminosities (similar to 3 x 10(-3) M-circle dot), then Betelgeuse's bow shock is very young and is unlikely to have reached a steady state. The circular nature of the bow shock shell is consistent with this conclusion. Thus, our results suggest that Betelgeuse only entered the red supergiant phase recently.

• 出版日期2012-5