麦哲伦星云中Be/Oe星和LGRB祖先星的ZAMS旋转速度
ZAMS rotational velocities of Be/Oe stars and LGRBs progenitors in the Magellanic Clouds
摘要：
大麦哲伦云和小麦哲伦云是在低金属丰度下对自转速度和恒星演化进行理论预测的有利环境。根据理论预测，B型恒星的自转速度在低金属丰度（LMC/SMC）环境中比在高金属丰度（MW）环境中更高。为了验证模型，我们观察了VLT-FLAMES 523 B和Be星，它们是目前在MC中观察到的这类天体中最大的样本。我们首先确定了恒星的基本参数，我们发现，B和Be星旋转速度在MC比在MW。我们还确定了平均ZAMS旋转速度与Be星质量的第一分布。这些结果表明Be星的出现与质量、金属丰度、恒星演化和恒星形成区有关。此外，最近的长伽马射线暴祖先的模型预测可能的LGRB祖先在SMC的金属丰度。我们面对这些模型与观察到的（ZAMS旋转速度，质量）分布的最快的旋转（Be和Oe星）在我们的样本。此外，我们比较了相应的预测率从我们的研究与观测率的LGRB。
英文摘要：
The Large and Small Magellanic Clouds are priviledged environments to perform tests of theoretical predictions at low metallicity on rotational velocities and stellar evolution. According to theoretical predictions, the rotational velocities of B-type stars are expected to be higher in low metallicity (LMC/SMC) than in high metallicity (MW) environments. To verify the models, we observed with the VLT-FLAMES 523 B and Be stars, which form, at the moment, the largest observed sample of these kind of objects in the MCs. We first determined the stellar fundamental parameters and we found that B and Be stars rotate faster in the MCs than in the MW. We also determined the first distribution of the average ZAMS rotational velocities versus the mass of Be stars. These results indicate that the appearance of Be stars is mass-, metallicity-, stellar evolution-, and star-formation regions-dependant. Moreover, the recent models of Long Gamma Ray Bursts progenitors foresee possible LGRBs progenitors at the SMC's metallicity. We confront these models with the observed (ZAMS rotational velocities, masses) distributions of the fastest rotators (Be and Oe stars) in our sample. Furthermore, we compare the corresponding predicted rates from our study with observed rates of LGRBs.
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