The B and Be Star Population of NGC 3766
The B and Be Star Population of NGC 3766
复制标题
DOI：
10.1086/523934
复制
发表时间：
2006-12
期刊：
影响因子：
--
通讯作者：
M. McSwain;Wenjin Huang;D. Gies;E. Grundstrom;E. Grundstrom;R. Townsend
中科院分区：
文献类型：
--
作者：
M. McSwain;Wenjin Huang;D. Gies;E. Grundstrom;E. Grundstrom;R. Townsend
我们对疏散星团NGC 3766的47个成员进行了多个时期的Hα光谱研究，以研究其Be星的长期变化。这个样本中的16颗恒星是Be星，包括一颗新发现的恒星。其中，我们观察到前所未有的11颗Be恒星在我们的Hα光谱中经历了盘状出现和/或接近消失，使其成为迄今为止已知的最多变的Be恒星群。因此，NGC 3766是研究Be星盘形成机制的绝佳地点。根据38个星团成员的蓝色光谱和现有的Strömgren星团光度测量，我们还测量了旋转速度、有效温度和极地表面重力，以研究可能导致Be现象的物理和进化因素。我们的分析还提供了NGC 3766的变红和距离的改进，我们发现E(B−V) = 0.22±0.03和（V−MV）0 = 11.6±0.2。Be星与主序演化的特定阶段无关，但它们是一群快速旋转的恒星，其速度分布通常与临界速度的70%-80%一致，尽管系统效应可能低估了真实的旋转速度，因此旋转更接近临界速度。我们对圆盘大小变化的测量结果与短暂的非径向脉动有助于形成这些高度变化的圆盘的想法是一致的。
We present multiple epochs of Hα spectroscopy for 47 members of the open cluster NGC 3766 to investigate the long-term variability of its Be stars. Sixteen of the stars in this sample are Be stars, including one new discovery. Of these, we observe an unprecedented 11 Be stars that undergo disk appearances and/or near disappearances in our Hα spectra, making this the most variable population of Be stars known to date. NGC 3766 is therefore an excellent location to study the formation mechanism of Be star disks. From blue optical spectra of 38 cluster members and existing Strömgren photometry of the cluster, we also measure rotational velocities, effective temperatures, and polar surface gravities to investigate the physical and evolutionary factors that may contribute to the Be phenomenon. Our analysis also provides improvements to the reddening and distance of NGC 3766, and we find E(B − V) = 0.22 ± 0.03 and (V − MV)0 = 11.6 ± 0.2, respectively. The Be stars are not associated with a particular stage of main-sequence evolution, but they are a population of rapidly rotating stars with a velocity distribution generally consistent with rotation at 70%-80% of the critical velocity, although systematic effects probably underestimate the true rotational velocities, so that the rotation is much closer to critical. Our measurements of the changing disk sizes are consistent with the idea that transitory, nonradial pulsations contribute to the formation of these highly variable disks.