Studies on properties of planet-host stars and on formation conditions of planets based on analyses of chemical compositions.

对73颗主星和18颗对比星进行了13种元素（C ~ Zn）的概略分析。将[Fe/H]与包括Fe和13种元素丰度的总金属丰度[M/H]进行比较，结果表明[M/H]相当于[Fe/H]值的0.75左右，并建议[M/H]应用作与缺金属区行星形成条件有关的金属丰度。行星巡天在一颗中等质量巨星周围发现了一颗热木星，它的质量被证明是中等质量恒星周围形成行星的新下限。结果表明，巨星中约有10颗恒星周围可能存在行星，铁丰度分布在太阳值附近，这与矮星的情况不同。在相关研究方面，我们在贫金属矮星和巨星样本中考察了α元素硫和硅的行为以及色球层的存在。在较低金属量区域，硫显示出相对于[Fe/H]+0.4 dex的平坦趋势。硅显示出类似于硫的行为，但它被证实，NLTE分析是必要的丰度分析的基础上近红外吸收线。在色球方面，观测证实了在矮星和巨星中色球的存在通常与金属丰度无关。

Abundance analyses of 13 elements (C to Zn) were carried out for 73 planet-host starsand 18 comparison stars. Comparison of [Fe/H] with a total metallicity [M/H] which includes abundances of Fe and 13 elements yielded the result that [M/H] corresponds to about 0.75 of [Fe/H] value, and suggested that [M/H] should be used as a metallicity concerning a condition for planet formation in the metal-deficient region. One hot Jupiter was detected around one intermediate-mass giant by planet survey, and its mass was turned out to be a new lower limit of planets being formed around intermediate-mass stars. It is found that about 10 stars of the giant sample may have planet around them, and that Fe abundances distribute around the solar value, which is different from dwarfs case. As for the related studies, behaviors of sulfur and silicon of alpha elements and existence of chromosphere were investigated in the sample of metal-poor dwarfs and giants. Sulfur shows a flat trend with +0.4 dex against [Fe/H] in a lower metallicity region. Silicon shows a behavior similar to sulfur, but it is confirmed that NLTE analyses are necessary for abundance analyses based on near infrared absorption lines. As for chromosphere, it is confirmed observationally that chromosphere exists in dwarfs and giants commonly independent of metallicity.