We present the first search for binary companions of Massive Young Stellar Objects (MYSOs) using AO-assisted $K$ band observations, with NaCo at the VLT. We have surveyed 32 MYSOs from the RMS catalogue, probing the widest companions, with a physical separation range of 400 - 46,000 au, within the predictions of models and observations for multiplicity of MYSOs. Statistical methods are employed to discern whether these companions are physical rather than visual binaries. We find 18 physical companions around 10 target objects, amounting to a multiplicity fraction of 31$\pm$8\% and a companion fraction of 53$\pm$9\%. For similar separation and mass ratio ranges, MYSOs seem to have more companions than T Tauri or O stars, respectively. This suggests that multiplicity increases with mass and decreases with evolutionary stage. We compute very rough estimates for the mass ratios from the $K$ band magnitudes, and these appear to be generally larger than 0.5. This is inconsistent with randomly sampling the IMF, as predicted by the binary capture formation theory. Finally, we find that MYSOs with binaries do not show any different characteristics to the average MYSO in terms of luminosity, distance, outflow or disc presence.
Binarity and beyond in A stars I. Survey description and first results of VLTI/GRAVITY observations of VAST targets with high Gaia-Hipparcos accelerations
Luminous blue variables: An imaging perspective on their binarity and near environment
上下文亮蓝变星（Luminous blue variable，LBV）是一种罕见的高光度大质量恒星。它们的特点是与瞬时喷发有关的强烈的测光和光谱变化。这些喷发的起源机制尚不清楚。此外，它们的形成仍然存在问题，伴侣的存在可能有助于解释它们是如何形成的。目标。本文介绍了对7个LBV（约占已知银河系人口的20%），一些沃尔夫-拉叶星和大质量双星的研究。我们用近、中、远红外图像探测这些大质量恒星周围的环境，调查潜在的星云/壳层和伴星。方法.为了研究大的空间尺度，我们使用了可见光限制和近衍射限制的自适应光学图像，以获得差异的诊断存在的拱星物质，并确定其程度。从这些图像中，我们还寻找了在宽轨道上存在的双星伴星。一旦发现了伴星，它与中心恒星的引力结合就会被测试。测试包括机会投影概率，自行估计与多历元观测，流量比，和恒星分离。结果我们发现，七分之二的LBV可能有一个宽轨道的伴侣。大多数LBV都有一个大的拱星包层或几个壳层。特别地，以其环而闻名的HD 168625具有几个壳体，该壳体可能具有大的冷壳体，环形成在该冷壳体的边缘处。这是我们第一次直接拍摄到LBV星的伴星。
Revealing Optically Hidden Companions to Intermediate-Mass Stripped Stars with Radial Velocities
University of Toronto（多伦多大学）；Dunlap Institute for Astronomy & Astrophysics, University of Toronto（多伦多大学邓普天文学与天体物理研究所）；Institute of Science and Technology Austria (ISTA)（奥地利科学与技术研究院）
