The blue straggler V106 in NGC6791: A prototype progenitor of old single giants masquerading as young
K. Brogaard, S. M. Christiansen, F. Grundahl, A. Miglio, R. G. Izzard, T. M. Tauris, E. L. Sandquist, D. A. VandenBerg, J. Jessen-Hansen, T. Arentoft, H. Bruntt… 展开作者
K. Brogaard, S. M. Christiansen, F. Grundahl, A. Miglio, R. G. Izzard, T. M. Tauris, E. L. Sandquist, D. A. VandenBerg, J. Jessen-Hansen, T. Arentoft, H. Bruntt, S. Frandsen, J. A. Orosz, G. A. Feiden, R. Mathieu, A. Geller, M. Shetrone, N. Ryde, D. Stello, I. Platais, S. Meibom
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12 pages, 7 figures, accepted for publication in MNRAS
We determine the properties of the binary star V106 in the old open cluster NGC6791. We identify the system to be a blue straggler cluster member by using a combination of ground-based and Kepler photometry and multi-epoch spectroscopy. The properties of the primary component are found to be $M_{\rm p}\sim1.67 \rm M_{\odot}$, more massive than the cluster turn-off, with $R_{\rm p}\sim1.91 \rm R_{\odot}$ and $T_{\rm eff}=7110\pm100$ K. The secondary component is highly oversized and overluminous for its low mass with $M_{\rm s}\sim0.182 \rm M_{\odot}$, $R_{\rm s}\sim0.864 \rm R_{\odot}$ and $T_{\rm eff}=6875\pm200$ K. We identify this secondary star as a bloated (proto) extremely low-mass helium white dwarf. These properties of V106 suggest that it represents a typical Algol-paradox system and that it evolved through a mass-transfer phase which provides insight into its past evolution. We present a detailed binary stellar evolution model for the formation of V106 using the MESA code and find that the mass-transfer phase only ceased about 40 Myr ago. Due to the short orbital period (P=1.4463 d) another mass-transfer phase is unavoidable once the current primary star evolves towards the red giant phase. We argue that V106 will evolve through a common-envelope phase within the next 100 Myr and merge to become a single over-massive giant. The high mass will make it appear young for its true age, which is revealed by the cluster properties. Therefore, V106 is potentially a prototype progenitor of old field giants masquerading as young.
On the origin of the short-period Blue Straggler Stars in Collinder 261: a binary evolution approach
Instituto de Astrofísica de La Plata, IALP (CONICET-UNLP)（拉普拉塔天体物理研究所（IALP，CONICET-UNLP））；INAF – Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所–阿尔切特里天体物理天文台）；European Southern Observatory（欧洲南方天文台）；Università di Padova（帕多瓦大学）；Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata (UNLP)（拉普拉塔国立大学天文与地球物理学院）
The role of mass transfer efficiency in stability criteria: Implementation in SEVN and a test on blue stragglers and binary compact objects
INAF – Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切尔西天文台）；Instituto de Astrofísica de Canarias（加那利群岛天体物理研究所）；Universidad de La Laguna（拉古纳大学）；Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona (UB)（巴塞罗那大学宇宙科学研究所）；Universität Heidelberg, Zentrum für Astronomie (ZAH), Institut für Theoretische Astrophysik（海德堡大学天文学中心理论天体物理研究所）；Universität Heidelberg, Interdiszipliäres Zentrum für Wissenschaftliches Rechnen（海德堡大学跨学科科学计算中心）；Dipartimento di Fisica e Astronomia Galileo Galilei, Università di Padova（帕多瓦大学伽利略·伽利莱物理与天文学系）；INFN, Sezione di Padova（意大利国家核物理研究所帕多瓦分部）；Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna（博洛尼萨大学物理与天文学系）
Finding binaries from phase modulation of pulsating stars with Kepler: V. Orbital parameters, with eccentricity and mass-ratio distributions of 341 new binaries
中间周期双星的轨道参数（$10^2$ - $10^3$ d）用常规方法很难测量，而且很不完整。我们对2224颗主序星A/F的光变曲线进行了新的测量，发现了341颗非食双星。我们计算了317个PB 1系统（单双星）和24个PB 2系统（双双星）的轨道参数。该方法可达到小的质量比$q=0.02$，并产生高度均匀的样品。我们参数化的质量比分布反演和MCMC的正演模拟技术，并发现它是偏向于低质量的同伴，峰值在$q=0.2$。虽然太阳型的原色显示棕矮星沙漠跨越中间时期，我们发现一个小的，但显着的（2.6 $σ$）人口的极端质量比同伴（$q<0.1$），我们的中间质量的原色。在100- 1500 d期间和在$q>0.1$，我们测量了当前A/F原色的二进制部分为15.4%$\pm$ 1.4%，尽管我们发现大部分的同伴（21% $\pm$ 6%）是质量转移后系统中的白矮星，其原色现在是蓝色离散星，其中一些是Ia型超新星，钡星，共生现象和相关现象。排除这些白矮星，我们发现原来的A/F原色的二进制分数是13.9%$\pm$ 2.1%在相同的参数空间。结合文献测量与我们的，我们发现在这些时期的二进制分数是一个常数5%的小学$M_1<0.8$ M $_{\odot}$，但随后增加与$\log M_1$线性，表明出生盘周围更大质量的原恒星$M_1>1$ M $_{\odot}$变得越来越容易破碎。最后，我们…
