标题： FUV对59 Cygni Be星疑似次矮星伴星的检测 显示英文标题

标题： FUV Detection of the Suspected Subdwarf Companion to the Be Star 59 Cygni

摘要： 我们报告在Be双星系统59 Cygni中检测到一个热次矮星成分。光谱特征是在光球模型光谱与国际紫外线探测卫星获得的远紫外光谱的交叉相关函数中发现的，我们使用交叉相关函数中的径向速度来确定双线光谱轨道。二元组件的个体光谱是通过多普勒断层扫描算法提取的。系统的通量由快速旋转的Be星主导。然而，次矮星贡献了大约4%的紫外通量，其光谱与热sdO星BD +75 325的光谱有很强的相似性。根据紫外光谱的外观和轨道元素，我们给出了恒星质量、半径和温度的估计。热伴星的存在导致面向伴星的Be盘外部分产生过量发射。我们提供了一组红色光谱，显示了在盘加热区域形成的He I 6678发射的轨道相位变化，这可能发生在盘的外边界附近。59 Cygni、FY Canis Majoris和phi Persei构成了已知的具有检测到的热演化伴星的Be双星组，这些是质量转移后的剥离残余物。它们的特性表明，一些Be星通过洛希瓣溢出的角动量转移被加速旋转。 显示英文摘要

摘要： We report on the detection of a hot subdwarf component in the Be binary system, 59 Cygni. The spectral signature is found in cross-correlation functions of photospheric model spectra with far-ultraviolet spectra obtained by the International Ultraviolet Explorer Satellite, and we used radial velocities from the cross-correlation functions to determine a double-lined spectroscopic orbit. The individual spectra of the binary components were extracted using a Doppler tomography algorithm. The flux of the system is dominated by the rapidly rotating Be star. However, the subdwarf contributes approximately 4% of the UV flux, and its spectrum bears a strong resemblance to that of the hot sdO star BD +75 325. Based upon the appearance of the UV spectrum and the orbital elements, we present estimates for the stellar masses, radii, and temperatures. The presence of the hot companion causes excess emission from the outer part of the Be disk facing the companion. We present a set of red spectra that show the orbital phase variations of the He I 6678 emission formed in the heated region of the disk, which probably occurs near the disk outer boundary. 59 Cygni, FY Canis Majoris, and phi Persei comprise the known set of Be binaries with detected hot evolved companions, which are the stripped down remains of mass transfer. Their properties demonstrate that some fraction of Be stars were spun up through angular momentum transfer by Roche lobe overflow.