天体matryoshka：Albireo系统的动力学和光谱分析
A celestial matryoshka: Dynamical and spectroscopic analysis of the Albireo system
摘要：
我们提出了一个光谱特性和一个新的轨道解的二元系统β Cyg Aa/Ac（MCA 55），著名的宽双星Albireo的主要组成部分（β Cyg A）。通过匹配的演化轨道的所有三个Albireo恒星（β天鹅座Aa，Ac和B）的物理参数，从光谱分析TIGRE和IUE光谱，我们确认，他们很可能是同时代的。我们最终的轨道解决方案是基于径向速度测量超过$120$年的基线，结合相对天体测量从散斑干涉观测和绝对天体测量从依巴谷和盖亚任务。我们最终的轨道解的周期为$121.65^{+3.34}_{-2.90}$年，偏心率为$0.20^{+0.01}_{-0.02}$。由于包含了绝对天体测量，我们发现质量比为$q = 1.25^{+0.19}_{-0.17}$，总质量为$9.47_{-3.24}^{+5.88}$ M $_\odot$，这表明次级星系（Ac）的质量更大。这些结果强烈地暗示了Albireo系统中第四个看不见的成员的存在。根据目前的光度数据，天鹅座β A本身很可能是一个层次结构的三元组。我们还推导出系统的自行，视线速度，和轨道视差的β天鹅座A系统，使我们能够定量评估的假设，Albireo A和B形成一个物理约束和家谱连接的系统。最后，我们发现了与Albireo共同的自行群的四个潜在成员，尽管没有任何地方像Albireo分量A到B那样接近。
英文摘要：
We present a spectroscopic characterisation and a new orbital solution for the binary system beta Cyg Aa/Ac (MCA 55), the primary component (beta Cyg A) of the well-known wide double star Albireo. By matching evolutionary tracks to the physical parameters of all three Albireo stars (beta Cyg Aa, Ac and B) as obtained from a spectroscopic analysis of TIGRE and IUE spectra, we confirm that they are likely coeval. Our final orbit solution is based on radial-velocity measurements taken over a baseline exceeding $120$ years, combined with relative astrometry from speckle interferometric observations and the absolute astrometry from the Hipparcos and Gaia missions. Our final orbit solution has a period of $121.65^{+3.34}_{-2.90}$ years with an eccentricity of $0.20^{+0.01}_{-0.02}$. Thanks to the inclusion of the absolute astrometry, we find a mass ratio of $q = 1.25^{+0.19}_{-0.17}$, and a total mass of $9.47_{-3.24}^{+5.88}$ M$_\odot$, indicating that the secondary (Ac) is the more massive of the pair. These results strongly suggest the presence of a fourth, unseen, member of the Albireo system. Given the current photometric data it is likely that beta Cyg A is itself a hierarchical triple. We also derive the systemic proper motion, line-of-sight velocity, and an orbital parallax of the beta Cyg A system, allowing us to quantitatively assess the hypothesis that Albireo A and B form a physically bound and genealogically connected system. Finally, we find four potential members of a common proper motion group with Albireo, though none anywhere as close by as the Albireo components A to B.
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