Colloquium on 13 February 2014
Circumstellar environments of massive stars


Title: Circumstellar environments of massive stars
Speaker: Jonathan Mackey (Argelander Institute for Astronomy, Bonn)
Date: Thursday, 13 February 2014
Time: 11:00 - 12:00
Venue: SAAO Auditorium


Massive stars drive strong winds and emit ionising radiation which
dramatically alters their surroundings.  At least 25 per cent of them
become runaway stars, travelling supersonically through the interstellar
medium.  For these stars, their circumstellar interaction usually
relaxes to a stationary state faster than the star evolves, making
comparison between theory and observations much simpler.  Cool red
supergiants like Betelgeuse have slow dense winds, and our numerical
simulations suggest that Betelgeuse’s bow shock is very young and may
still be expanding.  A model in which the star evolved recently from a
blue supergiant can successfully explain many (but not all) of the
observational constraints.  Younger, hot stars like Zeta Ophiuchi also
emit ionizing radiation that heats their surroundings.
Radiation-hydrodynamics simulations show that the dynamical impact of
photoionization heating on the interstellar medium can be much larger
than that of wind-driven bow shocks.

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