标题： 一个具有延伸主序转折的年轻星团：恒星自转情景预测的确认 显示英文标题

标题： A Young Cluster With an Extended Main Sequence Turnoff: Confirmation of a Prediction of the Stellar Rotation Scenario

摘要： 我们提供了对大麦哲伦星云中的NGC1850的哈勃空间望远镜测光数据，这是一个约1亿年，质量约为10^5太阳质量的星团。颜色-星等图清楚地显示了延伸主序星转折点（eMSTO）的存在。使用非旋转恒星等时线会导致约40百万年的年龄扩散。这与当在主序星转折点恒星中错误地将旋转效应解释为年龄扩散时预期的年龄范围相符。我们也没有发现星团内存在多个孤立的恒星形成爆发的证据，这与那些通过实际年龄扩散来解释eMSTO现象的场景相矛盾。因此，NGC 1850继续了eMSTO星团的趋势，其中推断出的年龄扩散与星团的年龄成比例。虽然我们的结果证实了由恒星旋转导致eMSTO特征的场景的一个关键预测，但需要对主序星转折点恒星的旋转速率进行直接测量，以确定性地确认或反驳恒星旋转是否是eMSTO现象的起因，或者是否是由于尚未发现的其他效应所致。 显示英文摘要

摘要： We present Hubble Space Telescope photometry of NGC1850, a ~100 Myr, ~10^5 Msun cluster in the Large Magellanic Cloud. The colour magnitude diagram clearly shows the presence of an extended main sequence turnoff (eMSTO). The use of non-rotating stellar isochrones leads to an age spread of ~40 Myr. This is in good agreement with the age range expected when the effects of rotation in MSTO stars are wrongly interpreted in terms of age spread. We also do not find evidence for multiple, isolated episodes of star-formation bursts within the cluster, in contradiction to scenarios that invoke actual age spreads to explain the eMSTO phenomenon. NGC 1850 therefore continues the trend of eMSTO clusters where the inferred age spread is proportional to the age of the cluster. While our results confirm a key prediction of the scenario where stellar rotation causes the eMSTO feature, direct measurements of the rotational rate of MSTO stars is required to definitively confirm or refute whether stellar rotation is the origin of the eMSTO phenomenon or if it is due to an as yet undiscovered effect.