Although the study of X-ray binaries has led to major breakthroughs in high-energy astrophysics, their circumbinary environment at scales of ∼100–10,000 au has not been thoroughly investigated. In this paper, we undertake a novel and exploratory study by employing direct and high-contrast imaging techniques on a sample of X-ray binaries, using adaptive optics and the vortex coronagraph on Keck/NIRC2. High-contrast imaging opens up the possibility to search for exoplanets, brown dwarfs, circumbinary companion stars, and protoplanetary disks in these extreme systems. Here we present the first near-infrared high-contrast images of 13 high-mass X-ray binaries located within ∼2–3 kpc. The key results of this campaign involve the discovery of several candidate circumbinary companions ranging from substellar (brown dwarf) to stellar masses. By conducting an analysis based on Galactic population models, we discriminate sources that are likely background/foreground stars and isolate those that have a high probability (≳60%–99%) of being gravitationally bound to the X-ray binary. This paper seeks to establish a preliminary catalog for future analyses of proper motion and subsequent observations. With our preliminary results, we calculate the first estimate of the companion frequency and the multiplicity frequency for X-ray binaries: ≈0.6 and 1.8 ± 0.9, respectively, considering only the sources that are most likely bound to the X-ray binary. In addition to extending our comprehension of how brown dwarfs and stars can form and survive in such extreme systems, our study opens a new window to our understanding of the formation of X-ray binaries.

中文翻译：

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使用 Keck/NIRC2 拍摄的首张近高质量 X 射线双星高对比度图像


尽管 X 射线双星的研究在高能天体物理学方面取得了重大突破，但其 100-10,000 au 尺度的双星周围环境尚未得到彻底研究。在本文中，我们利用自适应光学器件和 Keck/NIRC2 上的涡旋日冕仪，对 X 射线双星样本采用直接和高对比度成像技术，进行了一项新颖的探索性研究。高对比度成像为在这些极端系统中寻找系外行星、棕矮星、环绕双星伴星和原行星盘提供了可能性。在这里，我们展示了位于 ~2-3 kpc 范围内的 13 个高质量 X 射线双星的第一张近红外高对比度图像。这次活动的主要成果包括发现了从亚恒星（棕矮星）到恒星质量的几种候选环绕双星伴星。通过基于银河总体模型进行分析，我们区分了可能是背景/前景恒星的源，并隔离了那些很有可能 (≳60%–99%) 与 X 射线双星引力结合的源。本文旨在为未来自行分析和后续观测建立一个初步目录。根据我们的初步结果，我们计算了 X 射线双星的伴星频率和多重频率的第一个估计值：分别约为 0.6 和 1.8 ± 0.9，仅考虑最有可能与 X 射线双星结合的源。除了扩展我们对褐矮星和恒星如何在如此极端的系统中形成和生存的理解之外，我们的研究还为我们了解 X 射线双星的形成打开了一个新的窗口。