大质量恒星的粘性和离心不稳定性
Viscous and centrifugal instabilities of massive stars
摘要：
大质量恒星表现出各种各样的不稳定性，其中许多是知之甚少。我们探讨了大质量旋转恒星中离心力和角动量输运引起的不稳定性。首先，我们推导并数值求解了多变恒星模型中绝热径向模的线性化振荡方程。在差分旋转的存在下，我们表明，离心力和科里奥利力与粘性角动量输运相结合，可以激发恒星脉动模式，在低或高粘度条件下。在低粘度的限制，这是常见的在真正的明星，我们演示了如何计算模式的增长/阻尼率通过工作积分。最后，我们建立现实的旋转$30\,M_\odot$星模型，并表明，超稳定（增长）的径向模式预测存在的大部分恒星的生命，在没有非绝热效应。峰值增长率预计会发生，而明星是穿越赫兹-罗素差距，虽然非绝热阻尼可能占主导地位的粘性驱动，这取决于对流和/或磁转矩产生的有效粘度。粘性不稳定性可能是驱动大质量恒星脉动的一种新机制，并可能与亮蓝变星的不稳定性有关。
英文摘要：
Massive stars exhibit a variety of instabilities, many of which are poorly understood. We explore instabilities induced by centrifugal forces and angular momentum transport in massive rotating stars. First, we derive and numerically solve linearized oscillation equations for adiabatic radial modes in polytropic stellar models. In the presence of differential rotation, we show that centrifugal and Coriolis forces combined with viscous angular momentum transport can excite stellar pulsation modes, under both low- or high-viscosity conditions. In the low-viscosity limit, which is common in real stars, we demonstrate how to compute mode growth/damping rates via a work integral. Finally, we build realistic rotating $30\,M_\odot$ star models and show that overstable (growing) radial modes are predicted to exist for most of the star's life, in the absence of non-adiabatic effects. Peak growth rates are predicted to occur while the star is crossing the Hertzsprung-Russell gap, though non-adiabatic damping may dominate over viscous driving, depending on the effective viscosity produced by convective and/or magnetic torques. Viscous instability could be a new mechanism to drive massive star pulsations and is possibly related to instabilities of luminous blue variable stars.
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