Using high-quality spectra of the twin stars in the XO-2 binary system, we have detected significant differences in the chemical composition of their photospheres. The differences correlate strongly with the elements' dust condensation temperature. In XO-2N, volatiles are enhanced by about 0.015 dex and refractories are overabundant by up to 0.090 dex. On average, our error bar in relative abundance is 0.012 dex. We present an early metal-depletion scenario in which the formation of the gas giant planets known to exist around these stars is responsible for a 0.015 dex offset in the abundances of all elements while 20 M_Earth of non-detected rocky objects that formed around XO-2S explain the additional refractory-element difference. An alternative explanation involves the late accretion of at least 20 M_Earth of planet-like material by XO-2N, allegedly as a result of the migration of the hot Jupiter detected around that star. Dust cleansing by a nearby hot star as well as age or Galactic birthplace effects can be ruled out as valid explanations for this phenomenon.
翻译：使用 XO-2 二进制系统中双星的高质量光谱,我们发现其相片的化学构成存在显著差异,这些差异与元素的尘凝温度密切相关。在 XO-2N 中,挥发性被大约0.015 dex 和 亚焦体过大,最多为 0.090 dex 。平均而言,我们相对丰度的误差栏为 0.012 dex 。我们提出了一个早期的金属损耗假设,在这些恒星周围已知的气体巨行星的形成导致所有元素的丰度0.015 dex 抵消,而在XO-2S 周围形成的20 个非探测性岩石物体的地球,解释其他的相联性差异。另一种解释是XO-2N 的至少20 m_ 地球类似行星材料的延迟累积,据称这是在该恒星周围探测到的热木体迁移的结果。可以排除近处的热星以及年龄或银河生地效应的尘清洗,作为这一现象的正确解释。
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