标题： 利用蒙特卡罗模拟研究年轻低质量恒星的自转演化 显示英文标题

标题： Investigating the rotational evolution of young, low mass stars using Monte Carlo simulations

摘要： 我们通过蒙特卡洛模拟研究了年轻恒星的自转演化。 我们模拟了280,000颗恒星，每颗恒星被赋予一个质量、自转周期和吸积率。 吸积率随质量和时间变化，分别遵循幂律指数1.4和-1.5。 定义了一个与质量相关的吸积阈值，在此之下恒星被认为是无盘的，这导致了与观测结果一致的盘寿命分布。 恒星在吸积时以恒定角速度旋转，而在成为无盘后以恒定角动量演化。 我们重现了在几个年轻星团中观察到的双峰周期分布。 短周期峰值主要由无盘恒星组成，而长周期峰值则主要由吸积恒星占据。 两个分布都呈现出向长周期的长尾现象，并且在所有年龄阶段都观察到了缓慢旋转的无盘恒星。 我们重现了观测到的相关性，即盘分数与自转速率之间的关系，以及红外过量与自转周期之间的关系。 如果我们在最低质量恒星上释放盘锁定假设，从模拟中得出的周期-质量关系才表现出与年轻星团中观测到的相同全局趋势。 我们发现，对于吸积恒星，中位特定角动量的时间演化遵循幂律指数-0.65；而对于无盘恒星，则为-0.53，更浅的斜率源于盘寿命分布较宽。 使用基于观测的盘寿命、吸积率和初始自转周期分布，并从1到12百万年演化初始群体，我们重现了前主序角动量演化的主特征，这支持了盘锁定假设。 （摘要） 显示英文摘要

摘要： We investigate the rotational evolution of young stars through Monte Carlo simulations. We simulate 280,000 stars, each of which is assigned a mass, a rotational period, and a mass accretion rate. The mass accretion rate depends on mass and time, following power-laws indices 1.4 and -1.5, respectively. A mass-dependent accretion threshold is defined below which a star is considered as diskless, which results in a distribution of disk lifetimes that matches observations. Stars are evolved at constant angular spin rate while accreting and at constant angular momentum when they become diskless. We recover the bimodal period distribution seen in several young clusters. The short period peak consists mostly of diskless stars and the long period one is mainly populated by accreting stars. Both distributions present a long tail towards long periods and a population of slowly rotating diskless stars is observed at all ages. We reproduce the observed correlations between disk fraction and spin rate, as well as between IR excess and rotational period. The period-mass relation we derive from the simulations exhibits the same global trend as observed in young clusters only if we release the disk locking assumption for the lowest mass stars. We find that the time evolution of median specific angular momentum follows a power law index of -0.65 for accreting stars and of -0.53 for diskless stars, a shallower slope that results from a wide distribution of disk lifetimes. Using observationally-documented distributions of disk lifetimes, mass accretion rates, and initial rotation periods, and evolving an initial population from 1 to 12 Myr, we reproduce the main characteristics of pre-main sequence angular momentum evolution, which supports the disk locking hypothesis. (abridged)