IACOB项目。VI。关于ZAMS附近大质量O型星的难以捉摸的探测
The IACOB project. VI. On the elusive detection of massive O-type stars close to the ZAMS
摘要：
在零年龄主序星附近（年龄小于200万年）明显缺乏大质量O型星是一个被广泛讨论的话题。对这种难以捉摸的检测提出了不同的解释，但尚未得出确切的结论。我们重新评估了这一经验结果，受益于IACOB和OWN巡天收集的超过400颗银河系O型恒星的高质量光谱观测。我们使用来自iacob-gbat/快风光谱分析的温度和重力来在基尔和光谱HR图中定位我们的样品。我们评估了我们的恒星样本的完整性，使用银河系O型星表（GOSC）的信息的观测偏差，我们的方法的系统学，并与其他最近的研究使用较小的银河系O型恒星样本进行比较。我们的讨论基于光谱HR图，以避免使用不确定的距离。我们对年轻的Trumpler-14星系团进行了详细的研究，作为盖亚星系团距离如何帮助构建相关经典HR图的一个例子。ZAMS附近明显缺乏质量在30至70 Msol之间的大质量O型恒星，即使使用来自大型无偏差恒星样本的光谱结果也会持续存在。我们没有发现恒星的缺乏和观测偏差之间的相关性，我们的方法的局限性，或使用光谱HR图，而不是经典的。调查的质量吸积的效率在形成过程中，我们得出结论，吸积率向较低的值的调整可以调和检测到的O型星和理论出生线的热边界。最后，我们讨论了一个小样本的O2-O3.5恒星的存在下发现更接近ZAMS可能会解释考虑到非标准的恒星演化（例如，二进制的相互作用，合并，或均匀的演变）。
英文摘要：
The apparent lack of massive O-type stars near the zero-age main sequence (at ages < 2 Myr) is a topic widely discussed. Different explanations for this elusive detection have been proposed, but no firm conclusions have been reached yet. We reassess this empirical result benefiting from the high-quality spectroscopic observations of >400 Galactic O-type stars gathered by the IACOB and OWN surveys. We used temperatures and gravities from a iacob-gbat/fastwind spectroscopic analysis to locate our sample in the Kiel and spectroscopic HR diagrams. We evaluated the completeness of our sample of stars, observational biases using information from the Galactic O star catalog (GOSC), systematics of our methodology, and compare with other recent studies using smaller samples of Galactic O-type stars. We base our discussion on the spectroscopic HR diagram to avoid the use of uncertain distances. We performed a detailed study of the young cluster Trumpler-14 as an example of how Gaia cluster distances can help to construct the associated classical HR diagram. The apparent lack of massive O-type stars near the ZAMS with masses between 30 and 70 Msol persist even when spectroscopic results from a large, non-biased sample of stars are used. We do not find correlation between the dearth of stars and observational biases, limitations of our methodology, or the use of spectroscopic HR diagram instead of the classical one. Investigating the efficiency of mass accretion during the formation process we conclude that an adjustment of the accretion rate towards lower values could reconcile the hotter boundary of detected O-type stars and the theoretical birthline. Last, we discuss that the presence of a small sample of O2-O3.5 stars found closer to the ZAMS might be explained taking into account non-standard star evolution (e.g. binary interaction, mergers, or homogeneous evolution).
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
