论文标题
LMC中的狼射线星的合成种群,基于详细的单恒星进化模型
A synthetic population of Wolf-Rayet stars in the LMC based on detailed single and binary star evolution models
论文作者
论文摘要
毫无疑问,近距离二元系统中的传质为银河系和麦哲伦云的狼射线(WR)恒星的种群做出了贡献。但是,到目前为止,二进制构造通道还没有很好地探索。我们希望通过探索使用公开可用的台面代码计算的详细二进制和单星进化模型的大型网格来进行纠正。二进制模型是通过Roche-Lobe溢出和传质计算的,直到最初更庞大的恒星排出其核心。我们根据估计的恒星风光学深度来区分WR和氦星的模型。假设恒星形成恒定,我们使用这些模型来建立合成的WR人群。我们的模型可以将LMC的WR种群重现为重要的细节,包括主要WR亚型的数量和光度函数。我们发现,对于100%(50%)的二进制分数,所有LMC WR星以下$ 10^6 \,l _ {\ odot} $($ 10^{5.7} \,l _ {\ odot} $)都是剥离的二进制群众群体捐赠者。我们还确定了几种有见地的不匹配。我们的模型以50 \%的单星分数产生了太多的黄色超级巨头,呼吁较大的初始二元分数,或者在Humphreys-Davidson限制附近增加质量损失。我们的模型可以预测比观察到的更长周期的WR二进制文件,这可以说是由于对短期的观察偏见。我们的模型还低估了最短的WR二进制文件,这可能对理解双黑洞合并的祖细胞有影响。二进制生产的WR恒星的比例可能比经常假设的要大,并概述仅使用单个恒星模型来重现观察到的WR恒星时误解恒星物理的风险。
Without doubt, mass transfer in close binary systems contributes to the populations of Wolf-Rayet (WR) stars in the Milky Way and the Magellanic Clouds. However, the binary formation channel is so far not well explored. We want to remedy this by exploring large grids of detailed binary and single star evolution models computed with the publicly available MESA code, for a metallicity appropriate for the Large Magellanic Cloud (LMC). The binary models are calculated through Roche-lobe overflow and mass transfer, until the initially more massive star exhausts helium in its core. We distinguish models of WR and helium stars based on the estimated stellar wind optical depth. We use these models to build a synthetic WR population, assuming constant star formation. Our models can reproduce the WR population of the LMC to significant detail, including the number and luminosity functions of the main WR subtypes. We find that for binary fractions of 100% (50%), all LMC WR stars below $10^6\,L_{\odot}$ ($10^{5.7}\,L_{\odot}$) are stripped binary mass donors. We also identify several insightful mismatches. With a single star fraction of 50\%, our models produce too many yellow supergiants, calling either for a larger initial binary fraction, or for enhanced mass-loss near the Humphreys-Davidson limit. Our models predict more long-period WR binaries than observed, arguably due to an observational bias towards short periods. Our models also underpredict the shortest-period WR binaries, which may have implications for understanding the progenitors of double black hole mergers. The fraction of binary produced WR stars may be larger than often assumed, and outline the risk to mis-calibrate stellar physics when only single star models are used to reproduce the observed WR stars.