小流量可以提供向内迁移的最短周期行星
Small flow rate can supply inwardly migrating shortest-period planets
摘要：
发现的周期短至一天或更短的系外行星的数量令人惊讶，因为这些行星预计会以如此快的速度迁移到恒星中，这是由于行星在如此近的距离内在恒星上引起的潮汐。我们不太可能在行星生命的最后一小部分找到它们。最受欢迎的解决方案是，潮汐耗散比预期的要弱得多，这意味着最终的陨石坠落将是行星生命的一个更大的部分。我们没有理由排除这样一种解释，即少数行星不断地向内迁移，这些行星确实处于生命的最后阶段。在观察到中等行星的分布不利于潮汐耗散的显著弱于从双星观测中发现的情况之后，我们现在表明，在这样一个多余的行星向内迁移的“流”中，行星的数量足够低，甚至三天堆积的耗尽也是一个合理的来源。那么最短周期的出现分布将由行星不断被送入恒星形成，这可以解释开普勒场相对于太阳邻域的堆积的耗尽（Howard et al. 2012，下文简称H12）。由于开普勒在银道面上方进行观测，H12认为开普勒场可能包含了更古老的恒星群。恒星中由于巨行星引起的潮汐耗散强度可能并不比双星中弱多少。
英文摘要：
The number of exoplanets found with periods as short as one day and less was surprising given how fast these planets had been expected to migrate into the star due to the tides raised on the star by planets at such close distances. It has been seen as improbable that we would find planets in such a small final fraction of their lives. The favored solution has been that the tidal dissipation is much weaker than expected, which would mean that the final infall would be a larger fraction of the planets' life. We find no reason to exclude the explanation that a small number of planets are continuously sent migrating inwards such that these planets indeed are in the last fraction of their lives. Following the observation that the distribution of medium planets disfavors tidal dissipation being significantly weaker than has been found from observations of binary stars, we now show that the numbers of planets in such a "flow" of excess planets migrating inwards is low enough that even depletion of the three-day pileup is a plausible source. Then the shortest period occurrence distribution would be shaped by planets continuously being sent into the star, which may explain the depletion of the pileup in the Kepler field relative to the solar neighborhood (Howard et al. 2012, hereafter H12). Because Kepler observes above the galactic plane, H12 suggested the Kepler field may include an older population of stars. The tidal dissipation strength in stars due to giant planets may be not greatly weaker than it is in binary stars.
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