TAPIR Seminar

Massive stars play an important role in many astrophysical systems. However, their structures are highly uncertain and the observed properties are hard to understand based on 1D stellar evolution models. One issue is that these stars usually develop a super-Eddington envelope, which has caused a long standing challenge for 1D stellar evolution models. It has also been suspected to be responsible for the variability, large mass loss rate and giant eruptions of luminous blue variables (LBVs)  for a long time.  Here we use first principle three dimensional global radiation hydrodynamic simulations to show that convection caused by the iron opacity peak naturally produces an extended enveloped with episodic mass loss rate 10^-7-10^-5 solar mass per year.  The enhanced helium and hydrogen opacity peaks are responsible for the observed effective temperature of massive stars on the S Dor instability strip. The simulations also show that convection will cause the whole envelope to oscillate irregularly with a typical timescale of a few days and the luminosity can vary by 10-30\%.  Cooler stars with He/H opacity peaks show larger variability amplitude while the variation is smaller for hotter stars. I will discuss how these simulations can significantly improve our understanding on the structures, evolutions and mass loss of massive stars and how to connect the simulation results with the observed properties of massive stars directly.   [Please note: unusual venue:  Hameetman Auditorium, Cahill]