KELT-9b is an ultra-hot Jupiter observed to be undergoing extreme mass loss. Its A0-type host star has a radiative envelope, which makes its surface layers prone to retaining recently accreted material. To search for potential signs of planetary material polluting the stellar surface, we carry out the most comprehensive chemical characterisation of KELT-9 to-date. New element detections include Na and Y, which had previously been detected in the ultra-hot Jupiter but not studied in the star; these detections complete the set of ten elements measured in both star and planet. In comparing KELT-9 with similar open cluster stars we find no strong anomalies. This finding is consistent with calculations of photospheric pollution accounting for stellar mixing and using observationally estimated KELT-9b mass loss rates. We also rule out recent, short-lived intensive mass transfer such as the stellar ingestion of an Earth-mass exomoon.

中文翻译：

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KELT-9 及其超热木星：恒星参数、成分和行星污染

KELT-9b 是一颗超热木星，观察到它正在经历极度的质量损失。它的 A0 型主星有一个辐射包层，这使得它的表面层容易保留最近吸积的物质。为了寻找行星物质污染恒星表面的潜在迹象，我们对 KELT-9 进行了迄今为止最全面的化学表征。新元素检测包括 Na 和 Y，它们以前曾在超热木星中检测到，但未在恒星中进行过研究；这些检测完成了在恒星和行星中测量的十种元素。在将 KELT-9 与类似的疏散星团星进行比较时，我们没有发现任何强烈的异常现象。这一发现与解释恒星混合和使用观测估计的 KELT-9b 质量损失率的光球污染计算一致。我们也排除了最近，