标题： 多星系中的X射线源 显示英文标题

标题： X-Ray Sources in Multiple Stars

摘要： 亮X射线星经常出现在目视双星或多星系统中。具有几天周期的双星由于其快速的潮汐驱动自转，在常规非相对论性恒星中拥有最高的日冕X射线活动程度。然而，目视双星系统的轨道周期太大，使得伴星之间无法发生直接相互作用。我们认为，大多数已分辨双星中最强烈的X射线组分仍然是尚未被发现的短周期双星，并且少数是此类双星的合并遗迹。多星系统中短周期活动星的普遍存在，例如BY Dra型双星，可以通过三体系统（具有大相互倾角）的动力学演化来解释。内侧双星的动力扰动以循环方式增强偏心率，这一现象被称为科兹米诺夫循环。当近拱点接近时，潮汐摩擦减少双星的角动量，导致轨道收缩。当内侧双星的轨道周期下降到几天时，潮汐力会驱使伴星快速自转，从而将活动水平提高几个数量级。如果周期进一步下降，可能会发生合并，留下一个只有遥远伴星的快速旋转的活动矮星。 显示英文摘要

摘要： Luminous X-ray stars are very often found in visual double or multiple stars. Binaries with periods of a few days possess the highest degree of coronal X-ray activity among regular, non-relativistic stars because of their fast, tidally driven rotation. But the orbital periods in visual double stars are too large for any direct interaction between the companions to take place. We suggest that most of the strongest X-ray components in resolved binaries are yet-undiscovered short-period binaries, and that a few are merged remnants of such binaries. The omnipresence of short-period active stars, e.g. of BY-Dra-type binaries, in multiple systems is explained via the dynamical evolution of triple stars with large mutual inclinations. The dynamical perturbation on the inner pair pumps up the eccentricity in a cyclic manner, a phenomenon known as Kozai cycling. At times of close periapsis, tidal friction reduces the angular momentum of the binary, causing it to shrink. When the orbital period of the inner pair drops to a few days, fast surface rotation of the companions is driven by tidal forces, boosting activity by a few orders of magnitude. If the period drops still further, a merger may take place leaving a rapidly-rotating active dwarf with only a distant companion.