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

对73颗宿主星和18颗对照恒星进行了13种元素(C到Zn)的丰度分析。[Fe/H]与总金属丰度[M/H]的比较结果表明，[M/H]相当于[Fe/H]值的0.75左右，建议将[M/H]作为贫金属区行星形成条件的金属丰度。行星调查发现，在一颗中等质量巨星周围发现了一颗热木星，它的质量被证明是围绕中等质量恒星形成的行星的新下限。结果发现，在这个巨型样本中，大约有10颗恒星周围可能有行星存在，而且铁的丰度分布在太阳值附近，这与矮星的情况不同。在相关研究中，研究了贫金属矮星和巨星样品中α元素的硫和硅的行为以及色球的存在。在金属丰度较低的区域，硫对[Fe/H]呈平坦趋势，为+0.4Dex。硅表现出与硫相似的行为，但已证实基于近红外吸收线的丰度分析需要NLTE分析。至于色球，从观测上证实，色球存在于通常与金属丰度无关的矮星和巨星中。

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.