标题： 息变量中的红矮星是主序星吗？ 显示英文标题

标题： Are the red dwarfs in cataclysmic variables main-sequence stars?

摘要： 我们展示了短周期爆发型双星（轨道周期为$P < 3$小时）中的次星接近由单颗场星定义的具有太阳丰度的主序星。在爆发型双星中，具有$P > 3$小时轨道周期的系统，在给定周期下的最早光谱类型对应于主序星，而大多数次星具有较晚的光谱类型。可能的原因包括质量转移之前的核演化以及由于质量转移导致的热平衡缺乏。与使用最新恒星模型得到的演化序列进行比较表明，这些系统表现出异常高的转移率，并且有大量演化的供体系统。在所有研究得较为透彻的爆发型双星中，没有发现低金属丰度的次星。 显示英文摘要

摘要： We show that the secondaries in short-period cataclysmic variables with orbital periods $P < 3$ hr are close to the solar-abundance main sequence defined by single field stars. In cataclysmic variables with $P > 3$ hr, the earliest spectral types at a given period correspond to main sequence stars, while the majority of secondaries have later spectral types. Possible causes are nuclear evolution prior to mass transfer and lack of thermal equilibrium due to mass transfer. A comparison with evolutionary sequences obtained with up--to--date stellar models implies unusually high transfer rates and a large fraction of systems with evolved donors. There is no evidence for a secondary of low metallicity in any of the well-studied cataclysmic variables.