Effects of stellar evolution and ionizing radiation on the environments of massive stars

TL;DR

This paper explores how ionizing radiation and rapid stellar evolution influence the environments of massive stars, revealing their significant dynamical effects and explaining observed structures like Betelgeuse's bow shock.

Contribution

It provides new insights into the dynamical impact of ionizing photons and stellar evolution on massive star environments, supported by 3D simulations and observational explanations.

Findings

HII regions drive expanding shells and wakes around runaway O stars

Feedback from ionizing radiation surpasses stellar winds for late O stars

Rapid evolution of O stars explains transient circumstellar structures like Betelgeuse's bow shock

Abstract

We discuss two important effects for the astrospheres of runaway stars: the propagation of ionizing photons far beyond the astropause, and the rapid evolution of massive stars (and their winds) near the end of their lives. Hot stars emit ionizing photons with associated photoheating that has a significant dynamical effect on their surroundings. 3D simulations show that HII regions around runaway O stars drive expanding conical shells and leave underdense wakes in the medium they pass through. For late O stars this feedback to the interstellar medium is more important than that from stellar winds. Late in life, O stars evolve to cool red supergiants more rapidly than their environment can react, producing transient circumstellar structures such as double bow shocks. This provides an explanation for the bow shock and linear bar-shaped structure observed around Betelgeuse.