A peculiarity of metal-poor stars with planets?
A peculiarity of metal-poor stars with planets?
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拥有行星的贫金属恒星有何特点？
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
M. Haywood
中科院分区：
文献类型：
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作者：
M. Haywood
具有中等金属丰度（[-0.7，-0.2] dex）行星的恒星表现出与一般场恒星不同的性质。有13颗行星在这个金属丰度范围内的恒星属于厚盘，而在薄盘的恒星中只发现了一颗行星。虽然这个统计数据很弱，但它与行星存在和金属丰度之间的已知相关性相矛盾。我们将这一发现与薄盘在金属丰度范围内的特定属性相关联，其中恒星绕银河系旋转的速度比太阳快。它们的轨道参数很容易解释，如果它们是来自银河系外盘的污染物，作为径向混合的结果。这一点必须与太阳附近发现的富含金属的恒星（[Fe/H] > +0.1 dex）一起考虑，这些恒星是大多数探测到的行星的宿主，被怀疑是来自内银河系的流浪者。然后，人们质疑为什么起源于内部和外部薄盘的恒星分别显示出最高和最低的行星检测率。有人建议，巨行星的存在可能主要是一个函数的参数与银河系的中心半径，但不是金属丰度。结合现有的径向金属丰度梯度，然后径向混合解释了在高金属丰度的相关性，但也发现在低金属丰度的特殊性，这不能解释金属丰度和行星概率之间的简单相关性。
Stars with planets at intermediate metallicities ([–0.7, –0.2] dex) exhibit properties that differ from the general field stars. Thirteen stars with planets reported in this metallicity range belong to the thick disc, while only one planet have been detected among stars of the thin disc. Although this statistics is weak, it contradicts the known correlation between the presence of planet and metallicity. We relate this finding to the specific property of the thin disc in this metallicity range, where stars are shown to rotate around the Galaxy faster than the Sun. Their orbital parameters are conveniently explained if they are contaminants coming from the outer Galactic disc, as a result of radial mixing. This must be considered together with the fact that metal-rich stars ([Fe/H] > +0.1 dex) found in the solar neighbourhood, which are the hosts of most of the detected planets, are suspected of being wanderers from the inner Galactic disc. It is then questionned why stars that originate in the inner and outer thin disc show respectively the highest and lowest rate of detected planets. It is suggested that the presence of giant planets might be primarily a function of a parameter linked to galactocentric radius, but not metallicity. Combined with the existing radial metallicity gradient, then radial mixing explains the correlation at high metallicity observed locally, but also the peculiarity found at low metallicity, which cannot be accounted for by a simple correlation between metallicity and planet probability.