色球活动双星系统的多波长光学观测V. FF UMa（2 RE J0933 +624）：一个轨道周期变化的系统
Multiwavelength optical observations of chromospherically active binary systems V. FF UMa (2RE J0933+624): a system with orbital period variation
摘要：
这是一系列论文中的第五篇，旨在利用几种光学光谱指标研究活动双星系统的色球层，以获得或改进轨道解和基本恒星参数。本文介绍了一颗新发现的具有强H_α发射的X射线/EUV选择的活动双星FF UMa（2 RE J 0933 +624）的研究结果。这项工作的目标是找到轨道解，根据精确的径向速度确定恒星参数，并对色球活动的光学指标进行广泛研究。我们在1998年至2004年的五次观测中获得了高分辨率的阶梯光谱观测。我们发现径向速度交叉相关与径向速度标准星，以实现最佳的轨道解决方案。我们还用互相关技术测量了自转速度，并用银河空间速度分量（U、V、W）和Eggen判据研究了运动学。最后，我们已经确定了色球的贡献，在光学光谱指标，从钙II H & K钙II IRT线，使用光谱减法技术。我们已经发现，这个系统提出了一个轨道周期的变化，高于以前检测到的其他RS CVn系统。我们确定了一个改进的轨道解，找到了一个周期为3.274天的圆形轨道。我们导出了恒星参数，证实了主分量的亚巨星性质，并获得了主分量和次级分量的旋转速度（vsini）分别为33.57 km/s和32.38 km/s。从我们的运动学研究中，我们可以推断出它属于Castor运动群。最后，活动研究使我们更好地了解产生轨道周期变化的可能机制。
英文摘要：
This is the fifth paper in a series aimed at studying the chromospheres of active binary systems using several optical spectroscopic indicators to obtain or improve orbital solution and fundamental stellar parameters. We present here the study of FF UMa (2RE J0933+624), a recently discovered, X-ray/EUV selected, active binary with strong H_alpha emission. The objectives of this work are, to find orbital solutions and define stellar parameters from precise radial velocities and carry out an extensive study of the optical indicators of chromospheric activity. We obtained high resolution echelle spectroscopic observations during five observing runs from 1998 to 2004. We found radial velocities by cross correlation with radial velocity standard stars to achieve the best orbital solution. We also measured rotational velocity by cross-correlation techniques and have studied the kinematic by galactic space- velocity components (U, V, W) and Eggen criteria. Finally, we have determined the chromospheric contribution in optical spectroscopic indicators, from Ca II H & K to Ca II IRT lines, using the spectral subtraction technique. We have found that this system presents an orbital period variation, higher than previously detected in other RS CVn systems. We determined an improved orbital solution, finding a circular orbit with a period of 3.274 days. We derived the stellar parameters, confirming the subgiant nature of the primary component and obtained rotational velocities (vsini), of 33.57 km/s and 32.38 km/s for the primary and secondary components respectively. From our kinematic study, we can deduce its membership to the Castor moving group. Finally, the activity study has given us a better understanding of the possible mechanisms that produce the orbital period variation.
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