Effects of stellar evolution and ionizing radiation on the environments of massive stars
- 1Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
- 2South African Astronomical Observatory, P.O. Box 9, 7935 Observatory, South Africa
- 3Sternberg Astronomical Institute, Lomonosov Moscow State University, Universitetskij Pr. 13, Moscow 119992, Russia
- 4Department of Physics and Astronomy, East Tennessee State University, Box 70652, Johnson City, TN, 37614, USA
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. 3-D simulations show that H ii 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.