论文标题

30多拉德斯的BE型星的性质

Properties of the Be-type stars in 30 Doradus

论文作者

Dufton, P. L., Lennon, D. J., Villasenor, J. I., Howarth, I. D., Evans, C. J., de Mink, S. E., Sana, H., Taylor, W. D.

论文摘要

BE型恒星的进化状态尚不清楚,已经提出了单星和二元途径。在这里,分析了光谱型范围内73个BE型恒星B0-B3的VFTS光谱,以估计投影的旋转速度,径向速度和恒星参数。发现它们的旋转速度比相应的VFTS B型样品快,但模拟意味着它们的预计旋转速度与它们都以接近临界的速度旋转不一致。投影旋转速度估计的横向卷积导致平均旋转速度估计值为320-350 km/s,比相应的B型样品大约100 km/s。旋转速度小于临界速度的0.4的旋转速度缺乏目标,其分布范围为临界旋转。我们对旋转速度的平均值或中位数的最佳估计是临界速度的0.68。快速旋转的B型恒星比其BE类型的恒星多得多,而观察到的被鉴定为二元系统的BE型恒星的频率明显低于正常B型恒星的频率,与它们各自的radial型恒星一致。 BE型二进制文件的半疏松量也较小。对于以NGC346为中心的SMC BE型样品,发现了类似的结果,两个样品之间没有显着差异。将这些结果与BE型恒星的单一和二元恒星进化模型的预测进行了比较。假设单一机制主导了经典的BE类型恒星的产生,我们的比较将有利于二元进化史。

The evolutionary status of Be-type stars remains unclear, with both single-star and binary pathways having been proposed. Here, VFTS spectroscopy of 73 Be-type stars, in the spectral-type range, B0--B3, is analysed to estimate projected rotational velocities, radial velocities and stellar parameters. They are found to be rotating faster than the corresponding VFTS B-type sample but simulations imply that their projected rotational velocities are inconsistent with them all rotating at near critical velocities. The de-convolution of the projected rotational velocities estimates leads to a mean rotational velocity estimate of 320-350 km/s, approximately 100 km/s larger than that for the corresponding B-type sample. There is a dearth of targets with rotational velocities less than 0.4 of the critical velocity, with a broad distribution reaching up to critical rotation. Our best estimate for the mean or median of the rotational velocitiy is 0.68 of the critical velocity. Rapidly-rotating B-type stars are more numerous than their Be-type counterparts, whilst the observed frequency of Be-type stars identified as binary systems is significantly lower than that for normal B-type stars, consistent with their respective radial-velocity dispersions. The semi-amplitudes for the Be-type binaries are also smaller. Similar results are found for a SMC Be-type sample centred on NGC346 with no significant differences being found between the two samples. These results are compared with the predictions of single and binary stellar evolutionary models for Be-type stars. Assuming that a single mechanism dominated the production of classical Be-type stars, our comparison would favour a binary evolutionary history.

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