单线双星kappa Dra（B6 IIIe）中主Be星和次sdB星的动力学质量
Dynamical masses of the primary Be star and the secondary sdB star in the single-lined binary kappa Dra (B6 IIIe)
摘要：
由于许多经典Be星的性质可能是由于密近双星中的质量和角动量转移，因此它们的组分目前的质量、温度和半径对于与恒星演化模型进行比较是非常重要的。Kappa Dra是一个61.5天的单线双星，主要是B6 IIIe。利用CHARA阵列仪器MIRC/MIRC-X和MYSTIC，我们在H和K波段分别探测到了1.49 +- 0.10%和1.63 +- 0.09%的次级（近似光球层）通量比。从一个庞大而多样的光谱数据库中，只能提取出Be星的径向速度曲线。然而，使用依巴谷和盖亚的质量修正值，它们在标称的1-sigma误差范围内一致，我们可以得出Be星和伴星的总质量和发现的分量质量分别为3.65 +- 0.48 Msun和0.426 +- 0.043 Msun。先前观测到的远紫外光谱与sdO光谱模型模板的交叉相关没有检测到一个属于热O型亚矮星（sdO）的伴星，该伴星来自约20颗早期Be型恒星。在我们完整的3D轨道解的指导下，我们发现了一个被剥离的亚矮星B型伴星（远紫外线通量比为2.3 +- 0.5%）的强互相关信号，这使得第一个对这样的恒星进行了严格的表征，并使kappa Dra成为第一个具有直接观测到的亚矮星伴星的中晚期Be星。
英文摘要：
Because many classical Be stars may owe their nature to mass and angular-momentum transfer in a close binary, the present masses, temperatures, and radii of their components are of high interest for comparison to stellar evolution models. Kappa Dra is a 61.5-day single-lined binary with a B6 IIIe primary. With the CHARA Array instruments MIRC/MIRC-X and MYSTIC, we detected the secondary at (approximately photospheric) flux ratios of 1.49 +- 0.10% and 1.63 +- 0.09% in the H and K band, respectively. From a large and diverse optical spectroscopic database only the radial velocity curve of the Be star could be extracted. However, employing the parallaxes from Hipparcos and Gaia, which agree within their nominal 1-sigma errors, we could derive the total mass and found component masses of 3.65 +- 0.48 Msun and 0.426 +- 0.043 Msun for the Be star and the companion, respectively. Previous cross-correlation of the observed far-UV spectrum with sdO spectral model templates had not detected a companion belonging to the hot O-type subdwarf (sdO) population known from ~20 earlier-type Be stars. Guided by our full 3D orbital solution, we found a strong cross-correlation signal for a stripped subdwarf B-type companion (far-UV flux ratio of 2.3 +- 0.5%), enabling the first firm characterization of such a star, and making kappa Dra the first mid- to late-type Be star with a directly-observed subdwarf companion.
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