太阳附近最年轻的场星的光谱观测。I.光学明亮的样品
A spectroscopic survey of the youngest field stars in the solar neighbourhood. I. The optically bright sample
摘要：
我们提出的第一个结果进行1- 4米级望远镜的地面方案。我们的样本由1097颗活跃的、可能是年轻的恒星组成，它们都是北半球RASS X射线源的光学对应物。我们集中在704光学最亮（V_Ticho<=9.5等）的候选者。我们获得了高分辨率光谱的Halpha/Li光谱区426这样的恒星没有相关的文献数据。我们描述了样品和观察结果，并开始讨论其物理性质。我们使用了互相关技术和其他工具，以获得准确的径向/旋转速度，并进行光谱分类的单一和SB 2星。光谱相减技术被用来推导色球活动水平和锂丰度。我们估计了恒星软X射线巡天中年轻的单星和多系统的比例，以及更进化的系统（如RS CVn）的污染。我们根据Li丰度对恒星进行了分类，并对它们的天空分布进行了一瞥。样本似乎是年轻的昴宿星/毕宿星的混合物，加上一个较老的锂贫人口（~1-2 Gyr）。另外还发现了7颗锂丰度与IC 2602（约3000万年）或更年轻的恒星，尽管其中2颗似乎是富锂巨星。大量富锂巨行星的发现是这次调查的另一个成果。旧系统的活动水平是由潮汐同步增强的软X射线测量的污染是不可忽略的，特别是对K型星。5颗Li含量接近原始丰度的恒星可能与太阳附近已知的运动群有关。根据他们在人力资源图中的位置，其中一些人是PTTS候选人。
英文摘要：
We present the first results of a ground-based programme conducted on 1-4m class telescopes. Our sample consists of 1097 active and presumably young stars, all of them being optical counterparts of RASS X-ray sources in the northern hemisphere. We concentrate on the 704 optically brightest (V_Ticho<=9.5 mag) candidates. We acquired high-res spectroscopy in the Halpha/Li spectral regions for 426 of such stars without relevant literature data. We describe the sample and the observations and we start to discuss its physical properties. We used a cross-correlation technique and other tools to derive accurate radial/rotational velocities and to perform a spectral classification for both single and SB2 stars. The spectral subtraction technique was used to derive chromospheric activity levels and Li abundances. We estimated the fraction of young single stars and multiple systems in stellar soft X-ray surveys and the contamination by more evolved systems, like RS CVn's. We classified stars on the basis of Li abundance and give a glimpse of their sky distribution. The sample appears to be a mixture of young Pleiades-/Hyades- like stars plus an older Li-poor population (~1-2 Gyr). 7 stars with Li abundance compatible with the age of IC 2602 (~30 Myr) or younger were detected as well, although 2 appear to be Li-rich giants. The discovery of a large number of Li-rich giants is another outcome of this survey. The contamination of soft X-ray surveys by old systems in which the activity level is enhanced by tidal synchronisation is not negligible, especially for K-type stars. 5 stars with Li content close to the primordial abundance are probably associated with known moving groups in the solar neighbourhood. Some of them are PTTS candidates according to their positions in the HR diagram.
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