标题： 磁性Ap星为何旋转缓慢？ 显示英文标题

标题： Why are magnetic Ap stars slowly rotating?

摘要： 观测到的Ap星旋转数据表明，它们的大部分旋转速率形成一个与正常恒星分布不同的麦克斯韦分布，其平均值比正常恒星分布低3-4倍。 在主序星（MS）阶段没有发现显著角动量（AM）损失的证据。 因此得出结论，Ap星必须在其前主序星（pre-MS）演化阶段损失其初始角动量（AM）的大部分，这很可能是由于原始磁场与吸积盘和恒星风的相互作用所致。 从盘中获得的观测上最可接受的吸积率值为10^(-8) M_sun/年，通过磁化风的质量损失率也为10^(-8) M_sun/年，以及ZAMS时的表面磁场为1 kG，这些结果导致的角动量损失与观测结果完全一致。 存在一个独立的极慢旋转Ap星群体，其周期约为10-100年。 它们的数量太多，无法由描述大多数Ap星分布的模型产生。 推测它们极低的旋转速率是由于在主序星阶段额外的角动量损失所致。 显示英文摘要

摘要： Observational data on rotation of Ap stars suggest that the bulk of their rotation rates form a separate Maxwellian distribution with an average value 3-4 times lower than the normal star distribution. No evidences for a significant angular momentum (AM) loss on the main sequence (MS) have been found. It is thus concluded that Ap stars must lose a large fraction of their initial angular momentum (AM) in the pre-MS phase of evolution, most probably as a result of the interaction of their primordial magnetic fields with accretion disks and stellar winds. The observationally most acceptable values of accretion rate from the disk, 10^(-8) M_sun/year, of mass loss rate via a magnetized wind, 10^(-8) M_sun/year, and of the surface magnetic field, 1 kG on the ZAMS, result in the AM loss in full agreement with observations. There exists a separate group of extremely slowly rotating Ap stars, with periods of the order of 10-100 years. They are too numerous to come from the distribution describing the bulk of Ap stars. It is conjectured that their extremely low rotation rates are the result of additional AM loss on the MS.