标题： Be和B星的二进制分数和质量比：一项比较的VLT/NACO研究 显示英文标题

标题： The binary fraction and mass-ratio of Be and B stars: a comparative VLT/NACO study

摘要： 为了理解Be星周围的盘的形成机制，必须全面了解正常B星和Be星之间的差异和相似之处。 在这里，我们研究了一项之前的报告，该报告指出Be星可能拥有大量亚角秒级的伴星。 我们首次对使用相同设备观测的B星和Be星的匹配样本进行了系统、比较成像研究。 我们获得了40颗B星和39颗Be星的高角分辨率（0.07-0.1角秒）K波段自适应光学数据。 可探测的分离范围从0.1到8角秒（相当于20-1000 AU），理论上可以覆盖高达10个星等的亮度差异。 我们在37个Be目标中检测到11个双星系统（对应的双星比例为30 +/- 8%），在36个B目标中检测到10个双星系统（29 +/- 8%）。 进一步的测试表明，B星和Be星的双星系统不仅在频率上相似，在双星分离度、流量差异和质量比方面也显著相似。 我们发现，任何将双星伴星作为盘形成原因的假设都需要伴星距离小于20 AU。 已知近距离的伴星会影响Be星的周星盘，但由于并非所有Be星都被发现是近距离双星，数据表明双星性不能解释所有Be星的Be现象。 最后，双星参数本身的相似性也为Be星的形成机制提供了启示。 它们强烈表明，导致B星和Be星形成的初始条件在很大程度上是相似的。 这反过来表明，Be现象不是不同恒星形成机制的结果。 显示英文摘要

摘要： In order to understand the formation mechanism of the disks around Be stars it is imperative to have a good overview of both the differences and similarities between normal B stars and the Be stars. Here we investigate a previous report that there may be a large population of sub-arcsecond companions to Be stars. We present the first systematic, comparative imaging study of the binary properties of matched samples of B and Be stars observed using the same equipment. We obtained high angular resolution (0.07-0.1 arcsec) K band Adaptive Optics data of 40 B stars and 39 Be stars. The separations that can be probed range from 0.1 to 8 arcsec (corresponding to 20-1000 AU), and magnitude differences up to 10 magnitudes can in principle be covered. We detect 11 binaries out of 37 Be targets (corresponding to a binary fraction of 30 +/- 8%) and 10 binaries out of 36 B targets (29 +/- 8%). Further tests demonstrate that the B and Be binary systems are not only similar in frequency but also remarkably similar in terms of binary separations, flux differences and mass ratios. We find that any hypotheses invoking binary companions as responsible for the formation of a disk need the companions to be closer than 20 AU. Close companions are known to affect the circumstellar disks of Be stars, but as not all Be stars have been found to be close binaries, the data suggest that binarity can not be responsible for the Be phenomenon in all Be stars. Finally, the similarities of the binary parameters themselves also shed light on the Be formation mechanism. They strongly suggest that the initial conditions that gave rise to B and Be star formation must, to all intents and purposes, be similar. This in turn indicates that the Be phenomenon is not the result of a different star formation mechanism.