3D Smoothed Particle Hydrodynamics Models of Betelgeuse's Bow Shock

TL;DR

This paper presents the first 3D hydrodynamic simulations of Betelgeuse's bow shock, revealing its morphology depends on instability growth timescales and suggesting the shock is young and not in steady state.

Contribution

The study introduces 3D models of Betelgeuse's bow shock, analyzing instability effects and linking observations to the star's recent evolutionary phase.

Findings

Bow shock morphology varies with Rayleigh-Taylor and Kelvin-Helmholtz instability growth.

Observed low mass in the bow shock shell indicates a very young, non-steady state shock.

Betelgeuse may have recently entered the red supergiant phase.

Abstract

Betelgeuse, the bright red supergiant (RSG) in Orion, is a runaway star. Its supersonic motion through the interstellar medium has resulted in the formation of a bow shock, a cometary structure pointing in the direction of motion. We present the first 3D hydrodynamic simulations of the formation and evolution of Betelgeuse's bow shock. We show that the bow shock morphology depends substantially on the growth timescale for Rayleigh-Taylor versus Kelvin-Helmholtz instabilities. We discuss our models in light of the recent Herschel, GALEX and VLA observations. If the mass in the bow shock shell is low (~few x 0.001 Msun), as seems to be implied by the AKARI and Herschel observations, then Betelgeuse's bow shock is very young and is unlikely to have reached a steady state. The circular, smooth bow shock shell is consistent with this conclusion. We further discuss the implications of our results, in particular, the possibility that Betelgeuse may have only recently entered the RSG phase.