论文标题
恒星活性周期对有效温度的依赖性
The Dependence of Stellar Activity Cycles on Effective Temperature
论文作者
论文摘要
本文提出了这样一个想法，即观察到的恒星活性周期对旋转速率的依赖性可能表明对有效温度的依赖性更强。仅在旋转足够缓慢的情况下，召回了观察性证据，并为存在环状活性提供了理论上的论据。缓慢的旋转意味着靠近太阳能恒星旋转期间观察到的上限。此最大旋转周期取决于温度和较热的恒星的缩短。最大旋转周期被解释为大规模发电机操作的最小旋转速率。差分旋转和发电机的组合模型应用于不同质量旋转的恒星，速率略高于发电机的阈值速率。计算显示较热恒星的发电机周期较短。随着较热的恒星旋转的速度更快，计算出的循环也更短，以更快地旋转。观察到的较小恒星旋转期的较小的上限可以通过$α$效应的发作发电机的较大阈值振幅来解释：较大的$α$需要更快的旋转速度。计算中（循环）磁能的振幅与旋转周期及其上部键的差异成正比。如观察到的那样，具有中等不同旋转速率的恒星在其发电机的超临界性以及其磁性活性中可能会有显着差异。
This paper proposes the idea that the observed dependence of stellar activity cycles on rotation rate can be a manifestation of a stronger dependence on the effective temperature. Observational evidence is recalled and theoretical arguments are given for the presence of cyclic activity in the case of sufficiently slow rotation only. Slow rotation means proximity to the observed upper bound on the rotation period of solar-type stars. This maximum rotation period depends on temperature and shortens for hotter stars. The maximum rotation period is interpreted as the minimum rotation rate for operation of a large-scale dynamo. A combined model for differential rotation and the dynamo is applied to stars of different mass rotating with a rate slightly above the threshold rate for the dynamo. Computations show shorter dynamo cycles for hotter stars. As the hotter stars rotate faster, the computed cycles are also shorter for faster rotation. The observed smaller upper bound for rotation period of hotter stars can be explained by the larger threshold amplitude of the $α$-effect for onset of their dynamos: a larger $α$ demands faster rotation. The amplitude of the (cycling) magnetic energy in the computations is proportional to the difference between the rotation period and its upper bound for the dynamo. Stars with moderately different rotation rates can differ significantly in super-criticality of their dynamos and therefore in their magnetic activity, as observed.
