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| Paper: |
Nonlinear Pulsation Modeling of Luminous Blue Variables |
| Volume: |
135, A Half Century of Stellar Pulsation Interpretations: a Tribute to Arthur N. Cox |
| Page: |
307 |
| Authors: |
Despain, K. M.; Guzik, J. A.; Cox, A. N. |
| Abstract: |
We show the results of nonlinear hydrodynamic calculations of luminous blue variable envelope models based on first crossing evolution models of initial mass 50-80 solar masses including mass loss. The models are predicted in the linear analysis to pulsate in multiple radial and nonradial "strange" modes, with periods of 5-40 days, and growth rates well in excess of 100% per period. The models are calculated using an updated version of the Ostlie and Cox hydrodynamics code, and include the new OPAL opacities and time-dependent convection. The nonlinear models exhibit semi-regular pulsations in multiple modes, with radial velocity amplitudes 50-200 kmsec. The amplitudes decrease with increasing He abundance and consequent decrease in opacity in the deep driving layers. Under certain conditions, convection cannot turn on rapidly enough during a pulsation cycle to transport the required total luminosity, and the Eddington limit for the radiative luminosity is repeatedly exceeded. In these cases, models exhibit "outbursts", in which the outward photospheric velocity suddenly becomes very large, and the photospheric radius monotonically increases over several would-be pulsation cycles. We propose that this time-dependent convection mechanism may be responsible for S Doradus-type LBV outbursts. |
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