从天秤座$δ$表面碳氮丰度比看大陵五经典系统中的保守质量传递
Evidence for conservative mass transfer in the classical Algol system $δ$ Librae from its surface carbon-to-nitrogen abundance ratio
摘要：
大陵型双星系统是质量较大的组分与其伴星之间快速质量转移的产物。目前还不清楚这个过程是否是保守的，或者是否有大量的质量从系统中损失。一个系统在质量交换之前的历史记录在光球的化学成分中，特别是在碳氮比（C/N）中。我们用它来跟踪一个经典的Algol型系统，$δ$ Librae的组件中的传质过程的效率。目前的分析以新的光谱数据（地面高分辨率埃歇尔光谱）和提取的档案测光观测（STEREO卫星的天基测量）为基础。在轨道解中，考虑了径向速度变化的非开普勒效应。与以前的研究相比，这将主要的质量减少了1.1 \Msun \（$\sim$ 23\%），并消除了半径和有效温度之间长期存在的差异。光谱解缠技术应用于埃歇勒观测，分离各个分量的光谱。大气和丰度进行分析的质量增加的组成部分，我们发现C/N $= 1.55 \pm 0.40$的这颗星。计算了这两个组件的一组广泛的进化模型（$3.5\times10^6$），并从中推导出最佳拟合模型。结果表明，表征二元系统质量损失效率的参数$β$接近于零。这意味着$δ$ Lib中的质量传递大部分是保守的，系统的质量损失很小。
英文摘要：
Algol-type binary systems are the product of rapid mass transfer between the initially more massive component to its companion. It is still unknown whether the process is conservative, or whether substantial mass is lost from the system. The history of a system prior to mass exchange is imprinted in the photospheric chemical composition, in particular in the carbon-to-nitrogen (C/N) ratio. We use this to trace the efficiency of mass-transfer processes in the components of a classical Algol-type system, $δ$ Librae. The present analysis is based on new spectroscopic data (ground-based high-resolution échelle spectra) and extracted archival photometric observations (space-based measurements from the STEREO satellites). In the orbital solution, non-Keplerian effects on the radial-velocity variations were taken into account. This reduces the primary's mass by 1.1 \Msun\ ($\sim$23\%) significantly in comparison to previous studies, and removes a long-standing discrepancy between the radius and effective temperature. A spectral disentangling technique is applied to the échelle observations and the spectra of the individual components are separated. Atmospheric and abundance analyses are performed for the mass-gaining component and we found C/N $= 1.55 \pm 0.40$ for this star. An extensive set of evolutionary models ($3.5\times10^6$) for both components are calculated from which the best-fitting model is derived. It is found that $β$, the parameter which quantifies the efficiency of mass-loss from a binary system, is close to zero. This means that the mass-transfer in $δ$ Lib is mostly conservative with little mass loss from the system.
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