arXiv 2006.132292020-06-23astro-ph.SR

调查大质量Be星缺乏主序星伴星

Investigating the lack of main-sequence companions to massive Be stars

J. Bodensteiner, T. Shenar, H. Sana

备注：: 15 pages (incl. appendix), 6 figures, 3 tables, accepted for publication in A&A
发表信息：: A&A 641, A42 (2020)
DOI：: 10.1051/0004-6361/202037640

摘要：

B型星中约有20%是经典Be星。Be现象与快速旋转密切相关，其起源尚不清楚。它可能源于单星或双星的演化。在双星通道的框架中，最初质量更大的恒星将质量和角动量转移到原来的次级恒星，从而成为Be星。然后系统会演化成一颗Be双星，并有一颗后主序星伴星，这颗伴星可能会在后来的超新星事件中被破坏。因此，如果双星通道主导了Be星的形成，人们可能会期望强烈缺乏与主序星（MS）相伴的近距离Be双星。通过一个广泛的，逐星审查的文献的星系早期型Be恒星的星等有限的样本，我们调查是否被二进制MS同伴已知存在。我们的样本是从BeSS数据库构建的，并与所有可用的文献中的单个恒星进行交叉匹配。在505颗Be星的初始列表中，我们编译了287颗比B1.5更早的银河系Be星的最终样本，其中13个物体被报告为具有已知后MS同伴的Be双星，11个是未知，不确定或有争议的同伴。我们没有发现任何经证实的报告与MS同伴的二进制。对于剩下的263个目标，文献中没有关于多重性的重要报道，这意味着它们要么是有微弱伴星的Be双星，要么是真正的单星。明显缺乏MS的同伴被恒星，这与大量的检测到的B+B MS双星形成鲜明对比，强烈支持早期型Be星是双星相互作用的产物，从伴星转移质量和角动量后旋转的假设。从表面上看，我们的结果可能表明，大多数早期型Be星是通过双星质量转移形成的。

英文摘要：

About 20% of all B-type stars are classical Be stars. The Be phenomenon is strongly correlated with rapid rotation, the origin of which remains unclear. It may be rooted in single- or binary-star evolution. In the framework of the binary channel, the initially more massive star transfers mass and angular momentum to the original secondary, which becomes a Be star. The system then evolves into a Be binary with a post-main-sequence companion, which may later be disrupted in a supernova event. Hence, if the binary channel dominates the formation of Be stars, one may expect a strong lack of close Be binaries with main sequence (MS) companions. Through an extensive, star-by-star review of the literature of a magnitude-limited sample of Galactic early-type Be stars, we investigate whether Be binaries with MS companions are known to exist. Our sample is constructed from the BeSS database and cross-matched with all available literature on the individual stars. Out of an initial list of 505 Be stars, we compile a final sample of 287 Galactic Be stars earlier than B1.5 with V<=12 mag. Out of those, 13 objects were reported as Be binaries with known post-MS companions and 11 as binaries with unknown, uncertain or debated companions. We find no confirmed reports of Be binaries with MS companions. For the remaining 263 targets, no significant reports of multiplicity exist in the literature, implying that they are either Be binaries with faint companions, or truly single. The clear lack of reported MS companions to Be stars, which stands in contrast to the high number of detected B+B MS binaries, strongly supports the hypothesis that early-type Be stars are binary interaction products that spun up after mass and angular momentum transfer from a companion star. Taken at face value, our results may suggest that a large majority of the early-type Be stars have formed through binary mass-transfer.

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