Massive unseen compact companions to hot subluminous stars

中子星和恒星质量的黑洞是大质量恒星在超新星爆炸中结束生命的残余物。通常只有当物质从发光的恒星转移到致密天体，并从强烈加热的吸积物质发出明亮的X射线时，才可能在双星中探测到这些奇异的物体。然而，在分离的双星中，它们只能从可见恒星的多普勒反射运动中被探测到。在我们对分离的热亚矮星双星的初步研究中，我们利用了它们的轨道同步性，发现在我们的51个样本中，至少有3个肯定有非常大的但看不见的同伴，即中子星甚至黑洞。这一比例出人意料地大，因为这些物体被认为是稀有的。这种在银河系中大量存在的热矮星和大质量致密天体之间的新联系，可能会导致已知中子星和黑洞数量的大幅增加。然而，我们的分析受到选择效应的影响，目前还无法量化。只有通过更大的样本才能实现这一点。因此，我们启动了一项大型调查，以在比以前大得多的空间体积中寻找有大质量伴星的热亚星。S调查的高效目标预选策略保证了对海量同伴的高敏感度。确凿的证据将是一个高幅度、短周期的双星系统，因为它将排除任何对伴星性质的怀疑。这一结果将阐明中子星和黑洞作为分离双星中的伴星的数量，以及它们与X射线双星数量的进化联系。该项目还将揭示热次矮星的晕群特性，并允许探测银河系引力势。

Neutron stars and stellar-mass black holes are the remnants of massive stars ending their lifes in supernova explosions. Detecting these exotic objects is usually only possible in a binary, when matter is transferred from the luminous star to the compact object and bright X-rays are emitted from the strongly heated accreted material. In a detached binary, however, they can only be detected from the Dopper-reflex motion of the visible star. In our pilot study of detached hot subdwarf binaries we took advantage of their orbital synchronisation and found that at least three out of our sample of 51 must have very massive, but invisible companions, i.e. neutron stars or even black holes. This fraction is unexpectedly large because these objects are considered to be rare. This new connection between hot subdwarfs, which are numerous in our Galaxy, and massive compact objects may lead to a tremendous increase in the number of known neutron stars and black holes. However, our analysis suffers from selection effects which can not be quantified yet. This can only be achieved by a much larger sample. Therefore, we have initiated a large survey to search for hot subwarfs with massive companions in a much bigger space volume than before. High sensitivity to massive companions is ensured by the survey s efficient target pre-selection strategy. The smoking gun will be a high-amplitude, short-period binary system, because it will exclude any possibility of doubt about the nature of the companion. The results will shed light on the population of neutron stars and black holes as companions in detached binaries and their evolutionary link to the X-ray binary population. The project will also reveal the properties of the halo population of hot subdwarfs and allow the Galactic gravitational potential to be probed.