An updated classification scheme for transition O2-3.5If*/WN5-7 stars is presented, following recent revisions to the spectral classifications for O and WN stars. We propose that O2-3.5If*, O2-3.5If*/WN5-7 and WN5-7 stars may be discriminated using the morphology of Hbeta to trace increasing wind density as follows: purely in absorption for O2-3.5If* stars in addition to the usual diagnostics from Walborn et al.; P Cygni for O2-3.5If*/WN5-7 stars; purely in emission for WN stars in addition to the usual diagnostics from Smith et al. We also discuss approximate criteria to discriminate between these subtypes from near-IR spectroscopy. The physical and wind properties of such stars are qualitatively discussed together with their evolutionary significance. We suggest that the majority of O2-3.5If*/WN5-7 stars are young, very massive hydrogen-burning stars, genuinely intermediate between O2-3.5If* and WN5-7 subtypes, although a minority are apparently core helium-burning stars evolving blueward towards the classical WN sequence. Finally, we reassess classifications for stars exhibiting lower ionization spectral features plus Hbeta emission.
Spectral classification and properties of the O Vz stars in the Galactic O-Star Spectroscopic Survey (GOSSS)
在银河系O星光谱巡天（GOSSS）的基础上，对O Vz星进行了详细系统的研究。对目前使用的光谱分类标准进行了重新讨论，并通过增加一个基于He I 4471、He II 4542和He II 4686谱线等效宽度的定量标准，对Vz现象进行了重新校准。对比分析了新采用的光谱分类标准所产生的GOSSS O Vz和O V总体。O Vz恒星的位置进行了探测，显示出最极端的情况下，对最年轻的恒星形成区的浓度。发生的VZ光谱特性在太阳能金属丰度的环境中，预测的快风代码，也进行了研究，确认考虑到几个过程的重要性，正确的解释的现象。
Spectral classification of OB-type stars using tree-based ensemble methods and evaluation of their explainability
Instituto de Astrofísica de Canarias（加那利群岛天体物理研究所）；Departamento de Astrofísica, Universidad de La Laguna（拉各鲁纳大学天体物理学系）；Centro Multidisciplinario de Física, Vicerrectoría de Investigación, Universidad Mayor（马约尔大学多学科物理中心）；Instituto Universitario de Matemática Pura y Aplicada. Universitat Politècnica de València（瓦伦西亚理工大学纯数学和应用数学大学研究所）；European Southern Observatory（欧洲南方天文台）；Departamento de Matemática Aplicada, Universidad Nacional Autónoma de Honduras（洪都拉斯国立自治大学应用数学系）
