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首页> 外文期刊>The Astrophysical journal >ROTATIONAL VELOCITIES OF B STARS
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ROTATIONAL VELOCITIES OF B STARS

机译：B星的旋转速度

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摘要

We measured the projected rotational velocities of 1092 northern B stars listed in the Bright Star Catalogue (BSC) and calibrated them against the 1975 Slettebak et al. system. We found that the published values of B dwarfs in the BSC average 27% higher than those standards. Only 0.3% of the stars have rotational velocities in excess of two-thirds of the breakup velocities, and the mean velocity is only 25% of breakup, implying that impending breakup is not a significant factor in reducing rotational velocities. For the B8-B9.5 Ⅲ-Ⅴ stars the bimodal distribution in Ⅴ can be explained by a set of slowly rotating Ap stars and a set of rapidly rotating normal stars. For the BO-B5 Ⅲ-Ⅴ stars that include very few peculiar stars, the distributions in Ⅴ are not bimodal. Are the low rotational velocities of B stars due to the occurrence of frequent low-mass companions, planets, or disks? The rotational velocities of giants originating from late B dwarfs are consistent with their conservation of angular momentum in shells. However, we are puzzled by why the giants that originate from the early B dwarfs, despite having 3 times greater radii, have nearly the same rotational velocities. We find that all B-type primaries in binaries with periods less than 2.4 days have synchronized rotational and orbital motions; those with periods between 2.4 and 5.0 days are rotating within a factor 2 of synchronization or are " nearly synchronized." The corresponding period ranges for A-type stars are 4.9 and 10.5 days, or twice as large. We found that the rotational velocities of the primaries are synchronized earlier than their orbits are circularized. The maximum orbital period for circularized B binaries is 1.5 days and for A binaries is 2.5 days. For stars of various ages from 10~(7.5) to 10~(10.2) yr the maximum circularized periods are a smooth exponential function of age.
机译：我们测量了“亮星目录”（BSC）中列出的1092个北B星的预计旋转速度，并根据1975年Slettebak等进行了校准。系统。我们发现，BSC中B矮星的发布值平均比那些标准高27％。只有0.3％的恒星的旋转速度超过破裂速度的三分之二，平均速度仅为破裂速度的25％，这意味着即将发生的破裂并不是降低旋转速度的重要因素。对于B8-B9.5Ⅲ-Ⅴ类恒星，Ⅴ中的双峰分布可以用一组缓慢旋转的Ap恒星和一组快速旋转的正常恒星来解释。对于只有很少的特殊恒星的BO-B5Ⅲ-Ⅴ恒星，Ⅴ中的分布不是双峰的。 B恒星的低旋转速度是由于频繁出现的低质量伴星，行星或盘状运动引起的吗？来自晚期B矮星的巨人的旋转速度与其在壳中的角动量守恒相一致。但是，令我们感到困惑的是，为什么起源于早期B矮星的巨人尽管半径大3倍，却具有几乎相同的旋转速度。我们发现，周期小于2.4天的双星中的所有B型原核都有同步的旋转运动和轨道运动。周期在2.4到5.0天之间的广告客户会在同步系数2内轮换或“接近同步”。 A型星的相应周期范围是4.9天和10.5天，或两倍大。我们发现，原基的旋转速度比圆化它们的轨道更早同步。循环B二进制文件的最大轨道周期为1.5天，而A二进制文件的最大轨道周期为2.5天。对于从10〜（7.5）到10〜（10.2）年的各种年龄的恒星，最大的圆化周期是年龄的平滑指数函数。

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