标题： NGC 6611 601：包含离心磁层宿主恒星的热前主序光谱双星 显示英文标题

标题： NGC 6611 601: A hot pre-main sequence spectroscopic binary containing a centrifugal magnetosphere host star

摘要： W 601（NGC 6611 601）是已知的少数几颗磁性Herbig Ae/Be星之一。 我们报告了大量高分辨率光谱偏振数据的分析结果。 该恒星是一个之前未被报道过的光谱双星系统，由两颗质量比为1.8的B2型恒星组成，质量分别为12$_\odot$和 6.2$M_\odot$，轨道周期为110天且偏心率较高。 磁场属于次级星W 601 B。 H$\alpha$发射线的来源与W 601 B的离心磁层一致；因此，从本质上讲，它并非一颗经典的Herbig Be星，因为其发射线并非形成于吸积盘。 然而，通过光谱分析得出的低值$\log{g} = 3.8$以及该恒星属于年轻NGC 6611星团的事实，最能表明它处于主序前阶段。 从 H$\alpha$线和纵向磁场$\langle B_z \rangle$的变化推断出的自转周期为 1.13 天。Stokes$V$和$\langle B_z \rangle$的建模表明表面偶极磁场$B_{\rm d}$在 6 到$11$千高斯之间。 由于其强烈的辐射、快速的自转和强大的表面磁场，W 601 B 很可能是一种早期的 H$\alpha$-明亮磁性 B 型恒星（如 $\sigma$ Ori E）的前身。相比之下，主星显然是一种非磁性的（$B_{\rm d} < 300$ G）前主序早期 B 型恒星。 根据磁制动预期，非磁性主星的自转速度显然比磁性恒星快。 显示英文摘要

摘要： W 601 (NGC 6611 601) is one of the handful of known magnetic Herbig Ae/Be stars. We report the analysis of a large dataset of high-resolution spectropolarimetry. The star is a previously unreported spectroscopic binary, consisting of 2 B2 stars with a mass ratio of 1.8, masses of 12 M$_\odot$ and 6.2 $M_\odot$, in an eccentric 110-day orbit. The magnetic field belongs to the secondary, W 601 B. The H$\alpha$ emission is consistent with an origin in W 601 B's centrifugal magnetosphere; the star is therefore not a classical Herbig Be star in the sense that its emission is not formed in an accretion disk. However, the low value of $\log{g} = 3.8$ determined via spectroscopic analysis, and the star's membership in the young NGC 6611 cluster, are most consistent with it being on the pre-main sequence. The rotational period inferred from the variability of the H$\alpha$ line and the longitudinal magnetic field $\langle B_z \rangle$ is 1.13 d. Modelling of Stokes $V$ and $\langle B_z \rangle$ indicates a surface dipolar magnetic field $B_{\rm d}$ between 6 and $11$ kG. With its strong emission, rapid rotation, and strong surface magnetic field, W 601 B is likely a precursor to H$\alpha$-bright magnetic B-type stars such as $\sigma$ Ori E. By contrast, the primary is an apparently non-magnetic ($B_{\rm d} < 300$ G) pre-main sequence early B-type star. In accordance with expectations from magnetic braking, the non-magnetic primary is apparently more rapidly rotating than the magnetic star.