标题： Hipparcos 对附近 OB 联盟的普查 显示英文标题

标题： A Hipparcos census of the nearby OB associations

摘要： 基于 Hipparcos 的位置、自行和视差，给出了附近 OB 联盟恒星内容的全面普查。 通过结合 de Bruijne 改进的汇聚点方法与 Hoogerwerf 和 Aguilar 的“意大利面法”，识别了运动群。 使用蒙特卡罗模拟来估算预期的闯入场星数量。 列出了 12 个年轻恒星群的天文学成员，范围达约 650 pc。 这些包括 Sco OB2 的 3 个子群：上天蝎座 (Upper Scorpius)、上南十字座 (Upper Centaurus Lupus) 和下南十字座 (Lower Centaurus Crux)，以及 Vel OB2、Tr 10、Col 121、Per OB2、α Persei (Per OB3)、Cas-Tau、Lac OB1、Cep OB2 和一个新定义的群体，称为 Cep OB6。 选择程序修正了先前已知的天文学和测光学 B 型和 A 型成员列表，并识别了许多新成员，包括大量 F 型恒星，以及一些演化恒星，例如 Cep OB6 中的 WR 恒星 γ² Vel (Vel OB2) 和 EZ CMa (Col 121)，以及经典的造父变星 δ Cep。 在最近的联盟中，较晚型的成员包括 T Tauri 对象和其他前主序星。 由于距离较大或不利的运动学特性，在 R CrA、CMa OB1、Mon OB1、Ori OB1、Cam OB1、Cep OB3、Cep OB4、Cyg OB4、Cyg OB7 和 Sct OB2 区域中的运动群的天文学证据尚无定论。 确定的群组的平均距离系统性地小于之前的估计。 平均运动显示出一种系统性模式，这与 Gould 星环的关系进行了讨论。 在 12 个检测到的运动群中，有 6 个未出现在经典附近的 OB 联盟列表中。 太阳邻域中未绑定的年轻恒星群的数量可能比之前认为的要大得多。 显示英文摘要

摘要： A comprehensive census of the stellar content of the nearby OB associations is presented, based on Hipparcos positions, proper motions, and parallaxes. Moving groups are identified by combining de Bruijne's refurbished convergent point method with the `Spaghetti method' of Hoogerwerf & Aguilar. Monte Carlo simulations are used to estimate the expected number of interloper field stars. Astrometric members are listed for 12 young stellar groups, out to a distance of ~650 pc. These are the 3 subgroups Upper Scorpius, Upper Centaurus Lupus and Lower Centaurus Crux of Sco OB2, as well as Vel OB2, Tr 10, Col 121, Per OB2, alpha Persei (Per OB3), Cas-Tau, Lac OB1, Cep OB2, and a new group designated as Cep OB6. The selection procedure corrects the list of previously known astrometric and photometric B- and A-type members, and identifies many new members, including a significant number of F stars, as well as evolved stars, e.g., the Wolf-Rayet stars gamma^2 Vel (Vel OB2) and EZ CMa (Col 121), and the classical Cepheid delta Cep in Cep OB6. In the nearest associations the later-type members include T Tauri objects and other pre-main sequence stars. Astrometric evidence for moving groups in the fields of R CrA, CMa OB1, Mon OB1, Ori OB1, Cam OB1, Cep OB3, Cep OB4, Cyg OB4, Cyg OB7, and Sct OB2, is inconclusive, due to their large distance or unfavorable kinematics. The mean distances of the well-established groups are systematically smaller than previous estimates. The mean motions display a systematic pattern, which is discussed in relation to the Gould Belt. Six of the 12 detected moving groups do not appear in the classical list of nearby OB associations. The number of unbound young stellar groups in the Solar neighbourhood may be significantly larger than thought previously.