Models for the circumstellar medium of runaway massive stars: possible application to Betelgeuse.
by
Jonathan Mackey(Argelander Institute for Astronomy, Bonn)
→
Europe/Stockholm
FC61
FC61
Description
A significant fraction of massive stars are moving supersonically
through the interstellar medium (ISM), with their stellar winds
generating bow shocks. In post-main-sequence evolution these stars may
evolve rapidly from red to blue and vice versa on the
Hertzsprung-Russell diagram, with accompanying rapid changes to their
stellar winds and bow shocks. The ram pressure of the ISM can confine
wind material very close to the star, in contrast to stationary stars,
leading to potential observational consequences in supernova
lightcurves. I will first describe our ongoing project in Bonn to
investigate these processes, and then focus on the specific case of
young red supergiants (RSG). Observations and models suggest that the
bow shock produced by the nearby RSG Betelgeuse is very young (<30 kyr
old), hence Betelgeuse may have only recently become a RSG. To test this
possibility we have performed 2D hydrodynamic simulations to model a
runaway blue supergiant (BSG) undergoing the transition to a RSG near
the end of its life. The collapsing BSG wind-bubble induces a
bow-shock-shaped inner shell comparable to Betelgeuse's bow shock.
Surrounding this is the larger-scale retreating bow shock generated by
the now defunct BSG wind's interaction with the ISM. This structure is a
natural candidate for the bar feature located (at least in projection)
just in front of Betelgeuse's bow shock.
