标题： 通过风质量损失和双星相互作用的共时恒星质量函数演变 显示英文标题

标题： Evolution of Mass Functions of Coeval Stars through Wind Mass Loss and Binary Interactions

摘要： 准确确定恒星质量函数和恒星种群的年龄对于天体物理学的许多方面都是至关重要的。 我们分析了共时主序星的质量函数演化，包括单星和双星演化的所有相关方面。 我们表明，恒星团中质量函数上部的斜率可能与初始质量函数的斜率有很大不同。 大质量恒星的风致质量损失会导致恒星的积累，在质量函数的高质量端形成一个峰值，从而使质量函数的斜率变平。 密近双星系统中的质量吸积和合并会产生再生的双星产物尾部。 这些蓝离散星使单星质量函数的质量范围扩大了两倍，并且可能比其母恒星团年轻多达十倍。 因此，从接近转折点的最 massive 恒星推导出的集群年龄可能会有显著偏差。 为克服这些困难，我们建议使用恒星质量函数的双星尾部作为无歧义的时钟来推导集群年龄，因为双星尾部的开始位置标识了集群的转折质量。 这由旧恒星种群质量函数中的明显跳跃以及年轻恒星种群中的风致质量损失峰值所指示。 我们进一步根据它们的频率、双星分数和表观年龄来表征星团中的双星诱导的蓝离散星种群。 显示英文摘要

摘要： Accurate determinations of stellar mass functions and ages of stellar populations are crucial to much of astrophysics. We analyse the evolution of stellar mass functions of coeval main sequence stars including all relevant aspects of single- and binary-star evolution. We show that the slope of the upper part of the mass function in a stellar cluster can be quite different to the slope of the initial mass function. Wind mass loss from massive stars leads to an accumulation of stars which is visible as a peak at the high mass end of mass functions, thereby flattening the mass function slope. Mass accretion and mergers in close binary systems create a tail of rejuvenated binary products. These blue straggler stars extend the single star mass function by up to a factor of two in mass and can appear up to ten times younger than their parent stellar cluster. Cluster ages derived from their most massive stars that are close to the turn-off may thus be significantly biased. To overcome such difficulties, we propose the use of the binary tail of stellar mass functions as an unambiguous clock to derive the cluster age because the location of the onset of the binary tail identifies the cluster turn-off mass. It is indicated by a pronounced jump in the mass function of old stellar populations and by the wind mass loss peak in young stellar populations. We further characterise the binary induced blue straggler population in star clusters in terms of their frequency, binary fraction and apparent age.