Orbital period modulation and magnetic cycles in close binaries
Orbital period modulation and magnetic cycles in close binaries
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DOI：
10.1046/j.1365-8711.1998.01446.x
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发表时间：
1998-06
影响因子：
4.8
通讯作者：
Antonino Francesco Lanza;M. Rodonò;R. Rosner
中科院分区：
文献类型：
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作者：
Antonino Francesco Lanza;M. Rodonò;R. Rosner
我们讨论了密近双星中观测到的轨道周期调制，并重点关注了阿普尔盖特提出的机制，该机制将与磁活动周期相关的恒星内部自转变化与活动星的引力四极矩变化联系起来；这种四极矩的变化反过来迫使双星的轨道运动遵循活动星的活动水平。我们通过考虑这种相互作用的细节来推广这种方法，并开发了一些可以轻松以解析形式解决问题的示例。从这些结果出发，我们在不同类型的发电机模型框架内考虑自转和磁场产生之间的相互作用，这些模型已被提出来解释太阳和恒星的活动。我们展示了在活动双星中观测到的轨道周期调制如何为区分这些模型提供新的约束条件。特别是，我们研究了活动双星原型RS Canum Venaticorum的情况，并提出由恒星磁发电机驱动的扭转振荡可能解释了这颗恒星观测到的行为。还讨论了磁活动与轨道周期调制之间关系的其他可能应用，这些应用与最近发现的包含射电脉冲星以及对流的上主序星或晚型低质量伴星的双星系统有关。
We discuss the observed orbital period modulations in close binaries, and focus on the mechanism proposed by Applegate relating the changes of the stellar internal rotation associated with a magnetic activity cycle with the variation of the gravitational quadrupole moment of the active component; the variation of this quadrupole moment in turn forces the orbital motion of the binary stars to follow the activity level of the active star. We generalize this approach by considering the details of this interaction, and develop some illustrative examples in which the problem can be easily solved in analytical form. Starting from such results, we consider the interplay between rotation and magnetic field generation in the framework of different types of dynamo models, which have been proposed to explain solar and stellar activity. We show how the observed orbital period modulation in active binaries may provide new constraints for discriminating between such models. In particular, we study the case of the prototype active binary RS Canum Venaticorum, and suggest that torsional oscillations — driven by a stellar magnetic dynamo — may account for the observed behaviour of this star. Further possible applications of the relationship between magnetic activity and orbital period modulation, related to the recent discovery of binary systems containing a radio pulsar and a convecting upper main-sequence or a late-type low-mass companion, are discussed.