Viscous and centrifugal instabilities of massive stars

Abstract Massive stars exhibit a variety of instabilities, many which are poorly understood. We explore instabilities induced by centrifugal forces and angular momentum transport in massive rotating stars. First, we derive numerically solve linearized oscillation equations for adiabatic radial modes polytropic stellar models. In the presence differential rotation, show that Coriolis combined with viscous can excite pulsation modes, under both low- or high-viscosity conditions. low-viscosity limit, is common real stars, demonstrate how to compute mode growth/damping rates via work integral. Finally, build realistic 30 M⊙ star models overstable (growing) predicted exist most star’s life, absence non-adiabatic effects. Peak growth occur while crossing Hertzsprung-Russell gap, though damping may dominate over driving, depending on effective viscosity produced convective and/or magnetic torques. Viscous instability could be new mechanism drive pulsations possibly related luminous blue variable