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