Be星向临界极限的演化与Be星的起源
Evolution towards the critical limit and the origin of Be stars
摘要：
我们确定的机制，加速表面的主要序列演化过程中的单星。我们计算了112个恒星模型，四个不同的初始质量在3和60 M_sun之间，在四个不同的金属丰度在0和0.020之间，并与七个不同的值之间的比率欧米茄/欧米茄_crit在0.1和0.99。对于所有模型，计算一直进行到主层序演化结束或达到临界极限。在主序星的寿命期间，表面速度的演化是由纬向环流（将角动量带到表面）和恒星风造成的质量损失（将其移除）之间的相互作用造成的。这两种机制对金属丰度的依赖在确定每种金属丰度时起着关键作用，对于能够达到或至少接近临界极限的恒星，初始质量（光谱类型）的限制范围。目前的模型预测，在年龄在1000万年到2500万年之间的星团中，快速旋转恒星的频率更高。这是大多数Be星被观测到的年龄范围。
英文摘要：
We determine which are the mechanisms accelerating the surface of single stars during the Main Sequence evolution. We have computed 112 stellar models of four different initial masses between 3 and 60 M_sun, at four different metallicities between 0 and 0.020, and with seven different values of the ratio Omega/Omega_crit between 0.1 and 0.99. For all the models, computations were performed until either the end of the Main Sequence evolution or the reaching of the critical limit. The evolution of surface velocities during the Main Sequence lifetime results from an interplay between meridional circulation (bringing angular momentum to the surface) and mass loss by stellar winds (removing it). The dependence on metallicity of these two mechanisms plays a key role in determining for each metallicity, a limiting range of initial masses (spectral types) for stars able to reach or at least approach the critical limit. Present models predict a higher frequency of fast rotating stars in clusters with ages between 10 and 25 Myr. This is the range of ages where most of Be stars are observed.
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