We report the results of a statistical study of cyclical period changes in cataclysmic variables (CVs). Assuming the third-body hypothesis as the cause of period changes, we estimate the third-body mass, m ₃, and its separation from the binary, a ₃, for 21 CVs showing cyclical period changes from well-sampled observed-minus-calculated diagrams covering more than a decade of observations. The inferred a ₃ values are independent of the binary orbital period, P _orb, whereas the m ₃ values increase with P _orb by 1 order of magnitude from the shortest period (oldest) to the longest period (youngest) systems, implying significant mass loss from the third body with time. A model for the time evolution of the triple system is not able to simultaneously explain the observed behavior of the m ₃(P _orb) and a ₃(P _orb) distributions because the combined mass loss from the binary and the third body demands an increase in orbital separation by factors ∼140 as the binary evolves toward shorter P _orb's, in clear disagreement with the observed distribution. We conclude that the third-body hypothesis is statistically inconsistent and cannot be used to explain cyclical period changes observed in CVs. On the other hand, the diagram of the amplitude of the period change versus the CV donor-star mass is consistent both with the alternative hypothesis that the observed cyclical period changes are a consequence of magnetic activity in the solar-type donor star, and with the standard evolutionary scenario for CVs.

中文翻译：

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灾难性变量的周期性变化：统计研究


我们报告了灾难变量（CV）周期性变化的统计研究结果。假设第三体假设是周期变化的原因，我们估计第三体质量 m ₃及其与二元 a ₃的分离，对于 21 个 CV，显示来自良好采样的观测值减去计算值的周期性周期变化图表涵盖了十多年的观察结果。推断的 a ₃值与双星轨道周期 P _orb无关，而从最短周期（最古老）到最长周期（最年轻）系统，m ₃值随 P _orb增加 1 个数量级，这意味着显着的质量损失随着时间的推移从第三个身体。三重系统的时间演化模型无法同时解释观察到的 m ₃ (P _orb ) 和 a ₃ (P _orb ) 分布行为，因为二元系统和第三天体的组合质量损失需要增加当双星向更短的 P_球演化时，轨道间隔约 140 倍，这与观察到的分布明显不一致。我们得出的结论是，第三体假设在统计上是不一致的，不能用来解释在 CV 中观察到的周期性变化。另一方面，周期变化幅度与 CV 供体星质量的关系图与另一种假设一致，即观察到的周期性周期变化是太阳型供体星磁活动的结果，并且与CV 的标准进化场景。