Projected rotational velocities (v sin i) are presented for a sample of 350 early B-type main-sequence stars in the nearby Galactic disk. The stars are located within ~1.5?kpc from the Sun, and the great majority within 700?pc. The analysis is based on high-resolution spectra obtained with the MIKE spectrograph on the Magellan Clay 6.5?m telescope at the Las Campanas Observatory in Chile. Spectral types were estimated based on relative intensities of some key line absorption ratios and comparisons to synthetic spectra. Effective temperatures were estimated from the reddening-free Q index, and projected rotational velocities were then determined via interpolation on a published grid that correlates the synthetic FWHM of the He I lines at 4026, 4388 and 4471 ? with v sin i. As the sample has been selected solely on the basis of spectral types, it contains a selection of B stars in the field, in clusters, and in OB associations. The v sin i distribution obtained for the entire sample is found to be essentially flat for v sin i values between 0 and 150?km?s–1, with only a modest peak at low projected rotational velocities. Considering subsamples of stars, there appears to be a gradation in the v sin i distribution with the field stars presenting a larger fraction of the slow rotators and the cluster stars distribution showing an excess of stars with v sin i between 70 and 130?km?s–1. Furthermore, for a subsample of potential runaway stars we find that the v sin i distribution resembles the distribution seen in denser environments, which could suggest that these runaway stars have been subject to dynamical ejection mechanisms.
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机译：给出了附近银河系盘中350颗早期B型主序恒星样本的预计旋转速度（v sin i）。恒星位于距太阳约1.5？kpc的范围内，绝大多数位于700？pc以内。该分析基于在智利拉斯坎帕纳斯天文台的麦哲伦粘土6.5？m望远镜上用MIKE光谱仪获得的高分辨率光谱。光谱类型是根据一些关键线吸收率的相对强度以及与合成光谱的比较来估算的。根据无变红的Q指数估算有效温度，然后通过在已公布的网格上进行插值确定投影旋转速度，该网格将He I线的合成FWHM值与4026、4388和4471？罪过我由于仅根据光谱类型选择了样本，因此在野外，星团和OB关联中包含B星的选择。发现整个样品的v sin i分布对于v sin i值在0到150？km？s–1之间基本上是平坦的，在低的投影旋转速度下只有适度的峰值。考虑到恒星的子样本，v sin i分布似乎是有梯度的，场星占慢旋转体的比例更大，而星团星体分布则表现出v sin i在70至130？km之间的过量恒星。 s–1。此外，对于潜在失控恒星的子样本，我们发现v sin i分布类似于在较稠密环境中看到的分布，这可能表明这些失控恒星已经受到了动力喷射机制的影响。
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