论文标题
巨大恒星的粘性和离心不稳定性
Viscous and centrifugal instabilities of massive stars
论文作者
论文摘要
巨大的恒星表现出各种不稳定性，其中许多知识鲜为人知。我们探索了巨大旋转恒星中离心力和角动量转运引起的不稳定性。首先，我们得出多蚀恒星模型中绝热径向模式的线性化振荡方程。在存在差异旋转的情况下，我们表明离心力和科里奥利力与粘性角动量转运相结合可以在低或高粘度条件下激发出色的恒星脉动模式。在实际恒星中常见的低粘度极限中，我们演示了如何通过工作积分来计算模式的增长/阻尼率。最后，我们建立了逼真的旋转$ 30 \，m_ \ odot $ star模型，并表明在没有非绝热效果的情况下，预计大部分恒星一生中都存在过分稳定的（增长）径向模式。预计峰值生长速率将在恒星越过Hertzsprung-russell间隙时发生，尽管非绝热阻尼可能在粘性驾驶上占主导地位，这取决于对流和/或磁性扭矩产生的有效粘度。粘性不稳定性可能是驱动大量恒星搏动的一种新机制，并且可能与发光蓝色可变星的不稳定性有关。
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.
