The observational detection of a localized reduction in the small planet occurrence rate, sometimes termed a 'gap', is an exciting discovery because of the implications for planet evolutionary history. This gap appears to define a transition region in which sub-Neptune planets are believed to have lost their H/He envelope, potentially by photoevaporation or core powered mass loss, and have thus been transformed into bare cores terrestrial planets. Here we investigate the transition between sub-Neptunes and super-Earths using a real sample of observed small close-in planets and applying envelope evolution models of the H/He envelope together with the mass-radius diagram and a photoevaporation model. We find that photoevaporation can explain the H/He envelope loss of most super-Earths in 100Myr, although an additional loss mechanism appears necessary in some planets. We explore the possibility that these planets families have different core mass and find a continuum in the primordial population of the strongly irradiated super-Earths and the sub-Neptunes. Our analysis also shows that close-orbiting sub-Neptunes with R < 3.5 R_oplus typically lose ~ 30% of their primordial envelope.

中文翻译：

---

亚海王星和超级地球观测种群的H/He包络演化轨迹

由于对行星进化历史的影响，对小行星出现率的局部减少（有时称为“差距”）的观察检测是一个令人兴奋的发现。这个间隙似乎定义了一个过渡区域，在该区域中，亚海王星行星被认为已经失去了它们的 H/He 包层，可能是由于光蒸发或核心动力质量损失，因此已经转变为裸核的类地行星。在这里，我们使用观测到的小型近距离行星的真实样本，并应用 H/He 包络的包络演化模型以及质量半径图和光蒸发模型，研究亚海王星和超级地球之间的过渡。我们发现光蒸发可以解释 100Myr 中大多数超级地球的 H/He 包层损失，尽管在某些行星中似乎需要额外的损失机制。我们探索了这些行星家族具有不同核心质量的可能性，并在受到强烈辐射的超级地球和亚海王星的原始种群中找到了一个连续体。我们的分析还表明，R < 3.5 R_oplus 的近轨亚海王星通常会丢失约 30% 的原始包络。