Extra-solar planet search by radial velocity measurements of stars

在这个为期三年的项目中，我们完成了太阳系外行星搜索计划，即利用斯巴鲁望远镜（HDS）对300颗G巨星进行径向速度观测，并利用冈山天文台的HIDES高色散摄谱仪、中国兴隆站的NAOCCES和韩国胡根山的HOES跟踪这些候选行星的径向速度变化。结果，我们发现了5颗系外行星和1颗褐矮星，其结果发表在参考期刊上。除此之外，我们还提交了一篇关于发现4颗系外行星的论文。一个研究小组同时发现10颗系外行星的情况在世界上也是非常罕见的，我们现在可以很好地讨论中等质量恒星中的行星形成问题。在初步分析中，这些行星的轨道周期都超过了100天，对于中等质量的恒星，轨道周期似乎有一个下限， ...更多信息 这与太阳等矮星周围的行星的情况不同。如果这是真的，它给出了行星形成场景的一定限制。这些样本的增加可能会为这种情况提供坚实的基础。2006年在日本箱根和2007年在中国丽江举行了两次研讨会，来自日本、中国和韩国的科学家们分别在日本箱根和中国丽江举办了两次研讨会。在这些会议上，我们介绍了观测结果，讨论了观测方案，并开发了有关径向速度降低的软件。特别是在提高径向速度测量精度方面取得了巨大进展。以前的精度，冈山为5 m/s，虎根山为9 m/s，分别提高到2 m/s和4 m/s。我们在这些研讨会上的深入讨论可能会导致相互理解，重要的是光谱仪的仪器轮廓（IP）不应在相关波长上发生变化，IP的采样点应在过采样的意义上增加，即使用小像素尺寸的CCD。中国兴隆天文台的精度没有提高到10米/秒以下，但我们对未来如何提高径向速度精度充满信心。基于这些结果，我们正在考虑增加G-巨星周围的系外行星数量，并基于加强的统计数据，我们试图了解行星的形成。

In this three-year project, we have completed the extra-solar planet search program, that is, we tried to pick up the planet candidates by radial velocity observation of 300 G-giants with Subaru telescope (HDS), and followed up the radial velocity variations of these candidates with HIDES high dispersion spectrograph at Okayama Astrophysical Observatory, NAOCCES at Xinglong station in China, and HOES at Hugen san in Korea. As a result, we discovered 5 exoplanets and 1 brown dwarf, whose results were published in refereed journals. In addition to this, we submitted a paper on the discovery of 4 exoplanets. It is quite rare even in the world that one group accomplished the discovery of about 10 exoplanets, and we are now in a good position to discuss on the planet formation in intermediate mass stars. In a preliminary analysis, orbital periods of these planets are shown to be longer than 100days, and there seems to be a lower limit in orbital period for stars of intermediate mass range, … More which is a different situation from the planets around dwarf stars like the Sun. If this is true, it gives a certain limit on planet formation scenario. Increase of these sample might lead to give a firm foundation on this scenario. It is also shown that metallicity in the planet hovering stars is higher than that in non-hovering stars, which is a confirmation of the previous works.Scientists of Japan, China, and Korea had two workshops at Hakone in Japan in 2006 and at Lijiang in China in 2007, respectively. In these meeting, we presented the observational results and discussed on the observational plans, and developed the software concerning radial velocity reduction. In particular, we achieved a tremendous progress in improving accuracy of radial velocity measurement. Previous precision, 5m/s at Okayama and 9m/s at Hugen san are much improved into 2m/s and 4m/s, respectively. Our intensive discussion during these workshops could lead to the mutual understandings that it is important that instrumental profile (IP) of the spectrograph should not change over the relevant wavelength, and the sampling points for IP should be increased in a sense of over sampling, that is, use of CCD with a small pixel size. Accuracy at Xinglong in China was not improved into less than 10m/s, but we are confident about how to improve radial velocity accuracy in futur.Based on these results, we are considering increase in number of exoplanets around G-giants and based on the reinforced statistical data we try to understand planet formation Less