Recent investigations have revealed a surprising lack of close binaries among extreme horizontal branch (EHB) stars in the globular cluster NGC6752, at variance with the analogous sdB field stars. Another puzzling result concerns the derived spectroscopic masses for some EHB stars. The present paper extends our study of NGC6752 to M80 and NGC5986. Twenty-one horizontal branch stars (out of which 5 EHBs) in NGC5986 and 31 in M80 (11 EHBs) were observed during four consecutive nights. We measured radial velocity variations, temperatures, gravities, and helium abundances. By means of a statistical analysis, we detected one EHB close binary candidate per cluster. In M80, the best estimate of the close binary EHB fraction is f=12%, and even the lowest estimate of the binary fraction among field sdB stars can be ruled out within a 90% confidence level. Because of the small observed sample, no strong conclusions can be drawn on the close EHB binary fraction for NGC5986, although our best estimate is rather low (f=25%). For the discrepancy in spectroscopic derived masses with theoretical models observed in NGC6752, our analysis of M80 EHB stars shows a similar trend. For the first time, we report a clear trend in surface helium abundance with temperature. Our results show that the deficiency of close binaries among EHB stars is now confirmed in two, and possibly three, globular clusters. This feature is therefore not a peculiarity of NGC6752. Our analysis also proves that the strangely high spectroscopic masses among EHB stars are now confirmed in at least a second cluster. Our results confirm that f could be a function of the age of the sdB star population, but we find that recent models have some problem reproducing all observations.
The effect of unresolved binaries on globular cluster proper-motion dispersion profiles
对球状星团进行高精度的运动学研究需要对所有可能的污染源有准确的了解。在其他来源中，双星可以在运动学中引入系统偏差。使用一组Monte Carlo集群模拟不同的浓度和二进制分数，我们调查未解决的二进制自行运动色散曲线的影响，处理模拟像HST自行运动样本。由于球状星团朝着部分能量均分的状态演化，更多的大质量恒星会失去能量，降低它们的速度色散。因此，平均而言，双星有较低的速度色散，因为它们是更大质量的运动示踪剂。我们表明，在具有高二元分数（初始二元分数为50%）和高浓度（即，接近能量均分），未分辨的双星会在主序星的速度色散中引入一个依赖于颜色的偏差，其量级为0.1-0.3 km s $^{-1}$（相当于速度色散的$1-6$ %），最红的恒星具有较低的速度色散，这是由于污染双星的比例较高。这种偏差取决于区分双星和单星的能力，颜色-星等图的细节和光度误差。我们将我们的分析应用于NGC 7078（M15）的HSTPROMO数据集，并表明没有观察到归因于双星的影响，与星团的低双星比例一致。我们的工作表明，双星不显着偏置自行速度色散配置文件，但应考虑到运动学分析的误差预算。
Monte Carlo modelling of globular star clusters - many primordial binaries, IMBH formation
我们将讨论星团的演化与一个大的初始二元分数，高达95%。初始的二进制人口选择遵循Kroupa（1995）建议的不变轨道参数分布。星团演化的Monte Carlo MOCCA模拟与Milone et al.（2012）对光度联星的观测进行了比较。它表明，所观察到的依赖于集群质量的二进制分数和二进制分数的比例内和外的半质量半径的MOCCA模拟恢复良好。这是由于Marks，Kroupa & Oh（2011）描述的宽双星的强烈密度依赖破坏导致初始双星分数的快速下降。我们还讨论了一个新的方案，形成中等质量的黑洞在密集的星团。在这种情况下，中等质量的黑洞是由包含恒星质量黑洞的硬双星与其他恒星和双星的动力学相互作用形成的。我们将讨论启动中等质量黑洞形成过程的必要条件，以及其质量吸积率对整体星系团性质的依赖关系。
Resolving white dwarf binaries within globular clusters with LISA
Radboud University（拉德堡德大学）；Leiden University（莱顿大学）；University of Auckland（奥克兰大学）；SRON, Netherlands Institute for Space Research（荷兰空间研究所（SRON））；KU Leuven（荷语鲁汶大学）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）
Exploring the dynamical evolution of binary stars in multiple-population globular clusters
Indiana University（印第安纳大学）；Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文学中心）；Dipartimento di Fisica e Astronomia "Galileo Galilei", Univ. di Padova（帕多瓦大学伽利略·伽利莱物理与天文系）；Korea Astronomy and Space Science Institute（韩国天文学与空间科学研究所）；A. Mickiewicz University（亚当·密茨凯维奇大学）；Istituto Nazionale di Astrofisica - Osservatorio Astronomico di Padova（意大利国家天体物理研究所帕多瓦天文台）
