其他莫希干人怎么样了？指状对流稀释金属丰度的现实模式和观测意义
What happened to the other Mohicans? Realistic models of metallicity dilution by fingering convection and observational implications
摘要：
当一颗行星落在它的主星表面时，增加的高金属量物质并不像通常认为的那样留在表层，而是通过指状（热盐）对流稀释到内部。然而，到目前为止，这一过程发生的时间尺度仍然非常有限。使用最近测得的湍流混合率指进对流，我提供了可靠的数值和半解析估计的速度，增加的重元素流失到内部。我发现，相对金属丰度增强后下降了10倍以上的时间尺度，这只取决于主恒星的结构，并减少非常迅速，随着恒星质量的增加（从约1Gyr的1.3 M_sun星到10Myr的1.5 M_sun星）。这个结果提供了一个优雅的解释，缺乏观察到的趋势之间的金属丰度和对流区质量的行星轴承恒星。更重要的是，它强烈地表明，行星恒星的高金属丰度必须是原始起源的。最后，指状区被发现深入恒星，这一结果将提供一个简单的理论解释的测量更高的锂耗尽率在行星轴承恒星。
英文摘要：
When a planet falls onto the surface of its host star, the added high-metallicity material does not remain in the surface layers, as often assumed, but is diluted into the interior through fingering (thermohaline) convection. Until now, however, the timescale over which this process happens remained very poorly constrained. Using recently-measured turbulent mixing rates for fingering convection, I provide reliable numerical and semi-analytical estimates for the rate at which the added heavy elements drain into the interior. I find that the relative metallicity enhancement post-infall drops by a factor of ten over a timescale which depends only on the structure of the host star, and decreases very rapidly with increasing stellar mass (from about 1Gyr for a 1.3M_sun star to 10Myr for a 1.5M_sun star). This result offers an elegant explanation to the lack of observed trend between metallicity and convection zone mass in planet-bearing stars. More crucially, it strongly suggests that the statistically-higher metallicity of planet-bearing stars must be of primordial origin. Finally, the fingering region is found to extend deeply into the star, a result which would provide a simple theoretical explanation to the measurements of higher lithium depletion rates in planet-bearing stars.
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