关于有裸氦施主的X射线双星的稀有性
On the Rarity of X-Ray Binaries with Naked Helium Donors
摘要：
多年来，银河系中缺乏已知的高质量X射线双星（HMXB）和裸露的氦供体星（以下简称氦星），这是一个令人惊讶的事实，因为银河系中有大量的HMXB含有富氢供体，这被认为是它们的祖先。最近的观测发现，在围绕中子星（NS）运行的HMXB中存在大量松散结合的Be施主，预计这些施主将通过向NS和共包络（CE）相的动态质量转移自然演变为He-HMXB，这进一步加剧了这种对比。因此，将大量的Be-HMXB与只有一个He-HMXB的观测相协调可以帮助限制CE物理的动力学。在这里，我们使用详细的恒星结构和演化模型，并表明，二进制合并的HMXB在CE事件必须是常见的，以解决这些观察到的人口之间的紧张局势。我们发现，定量地说，这种情况下仍然与CE演变的通常采用的能量参数化，产生预期的人口与目前的观察不一致。然而，未来的观察，更好地约束松散结合的O/B-NS二进制的基础人口可能会放置显着的限制CE弹射的效率。
英文摘要：
The paucity of known High-Mass X-Ray Binaries (HMXB) with naked He donor stars (hereafter He star) in the Galaxy has been noted over the years as a surprising fact, given the significant number of Galactic HMXBs containing H-rich donors, which are expected to be their progenitors. This contrast has further sharpened in light of recent observations uncovering a preponderance of HMXBs hosting loosely bound Be donors orbiting neutron stars (NS), which would be expected to naturally evolve into He-HMXBs through dynamical mass transfer onto the NS and a common-envelope (CE) phase. Hence, reconciling the large population of Be-HMXBs with the observation of only one He-HMXB can help constrain the dynamics of CE physics. Here, we use detailed stellar structure and evolution models and show that binary mergers of HMXBs during CE events must be common in order to resolve the tension between these observed populations. We find that, quantitatively, this scenario remains consistent with the typically adopted energy parameterization of CE evolution, yielding expected populations which are not at odds with current observations. However, future observations which better constrain the underlying population of loosely bound O/B-NS binaries are likely to place significant constraints on the efficiency of CE ejection.
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