arXiv 1312.45442013-12-16astro-ph.SR

热脉冲渐近巨星分支星的核质量增长和恒星寿命

The Core Mass Growth and Stellar Lifetime of Thermally Pulsing Asymptotic Giant Branch Stars

Jason S. Kalirai, Paola Marigo, Pier-Emmanuel Tremblay

备注：: 14 pages, 7 figures, 4 tables. Accepted for publication in ApJ
DOI：: 10.1088/0004-637X/782/1/17

摘要：

通过对四个年轻星团中白矮星的研究，建立了初末质量关系的中间质量范围的新约束，并将其应用于热脉冲渐近巨星分支（TP-AGB）恒星演化的研究.我们发现，恒星的核心质量的AGB增长迅速，从10%到30%的恒星与$M_{\rm initial}$ = 1.6到2.0 $M_\odot$。在较大的质量下，在$M_{\rm initial}$ = 3.4 $M_\odot$时，核心质量增长稳定地降低至$\sim$ 10%。这些观察结果与Marigo等人（2013）最新TP-AGB进化模型的预测非常一致。我们还比较了模型与不同的效率的第三次疏浚和质量损失，并证明了该过程的核心的增长主要是恒星风，而第三次疏浚起着次要的，但不可忽视的作用。基于新的白矮星测量结果，我们对文献中最流行的质量损失处方进行了探索性校准。最后，我们估计了TP-AGB上恒星的寿命和积分光度，对于$M_{\rm initial}$ $\sim$ 2 $M_\odot$，其峰值为$t$ $\sim$ 3 Myr和$E$ = 1.2 $\times$ 10 $L_\odot$ yr（$t$ $\sim$ 2 Myr，亮度比$\log(L/L_{\odot})$ $>$ 3.4的RGB尖端更亮），对于$M_{\rm initial}$ $\sim$ 3.5 $M_\odot$的恒星，$t$ = 0.4 Myr，$E$ = 6.1 $\times$ 10 $^{9}$ $L_\odot$ yr。这些结果的影响进行了讨论相对于一般人口合成研究，需要正确的TP-AGB阶段恒星演化的建模。

英文摘要：

We establish new constraints on the intermediate-mass range of the initial-final mass relation by studying white dwarfs in four young star clusters, and apply the results to study the evolution of stars on the thermally pulsing asymptotic giant branch (TP-AGB). We show that the stellar core mass on the AGB grows rapidly from 10% to 30% for stars with $M_{\rm initial}$ = 1.6 to 2.0 $M_\odot$. At larger masses, the core-mass growth decreases steadily to $\sim$10% at $M_{\rm initial}$ = 3.4 $M_\odot$. These observations are in excellent agreement with predictions from the latest TP-AGB evolutionary models in Marigo et al. (2013). We also compare to models with varying efficiencies of the third dredge-up and mass loss, and demonstrate that the process governing the growth of the core is largely the stellar wind, while the third dredge-up plays a secondary, but non-negligible role. Based on the new white dwarf measurements, we perform an exploratory calibration of the most popular mass-loss prescriptions in the literature. Finally, we estimate the lifetime and the integrated luminosity of stars on the TP-AGB to peak at $t$ $\sim$ 3 Myr and $E$ = 1.2 $\times$ 10$^{10}$ $L_\odot$ yr for $M_{\rm initial}$ $\sim$ 2 $M_\odot$ ($t$ $\sim$ 2 Myr for luminosities brighter than the RGB tip at $\log(L/L_{\odot})$ $>$ 3.4), decreasing to $t$ = 0.4 Myr and $E$ = 6.1 $\times$ 10$^{9}$ $L_\odot$ yr for stars with $M_{\rm initial}$ $\sim$ 3.5 $M_\odot$. The implications of these results are discussed with respect to general population synthesis studies that require correct modeling of the TP-AGB phase of stellar evolution.

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