论文标题
如何漂流和蒸发鹅卵石形状巨型行星III：WASP-77A B和$τ$BOötisb的形成
How drifting and evaporating pebbles shape giant planets III: The formation of WASP-77A b and $τ$ Boötis b
论文作者
论文摘要
人们认为大气丰度限制了行星形成途径，因为不同的物种在不同的温度下蒸发，在积聚大气中留下不同的特征。由于h $ _2 $ o，co $ _2 $，ch $ _4 $和CO的冷凝序列，行星c/o比率被认为会限制行星形成途径，从而导致气相C/O比的增加随距离的增加。在这里，我们使用圆盘演化模型，包括卵石生长，漂移和蒸发，再加上行星形成模型，其中包括卵石和气体积聚以及行星迁移，以计算巨型行星的大气组成。我们将结果与最近对热木星WASP-77A B和$τ$Boötisb的观察结果进行了比较，后者分别具有亚光和超极的C/H和O/H值。我们的模拟复制了这些测量结果，并表明像WASP-77A B之类的巨人应该开始形成Co $ _2 $蒸发前线，而$τ$BoötisB之类的巨人应源自H $ _2 $ O线。我们的模型允许形成子和超极性大气组成。但是，没有卵石蒸发的模拟无法再现$τ$BoötisB的大气的超极C/H和O/H比，而没有额外的固体积聚。我们将圆盘的$α$粘度参数确定为关键成分，因为粘度驱动挥发性富含蒸气的内向运动，负责气态C和O的积聚。取决于地球的迁移历史记录历史记录的迁移顺序，预计会在大气C/H和O/H大气C/H和O/H中。我们的模拟还可以预测$τ$boötisb和太阳能N/H的Super-Solar N/H，对于WASP-77A b。我们得出的结论是，卵石蒸发是解释系外行星大气种类的关键要素，因为它可以解释亚阳性大气的丰度。
Atmospheric abundances are thought to constrain the planet formation pathway, because different species evaporate at different temperatures leaving distinct signatures in the accreted atmosphere. The planetary C/O ratio is thought to constrain the planet formation pathway, because of the condensation sequence of H$_2$O, CO$_2$, CH$_4$, and CO, resulting in an increase of the gas phase C/O ratio with increasing distance. Here we use a disc evolution model including pebble growth, drift and evaporation coupled with a planet formation model that includes pebble and gas accretion as well as planet migration to compute the atmospheric compositions of giant planets. We compare our results to the recent observations of the hot Jupiters WASP-77A b and $τ$ Boötis b, which feature sub-solar and super-solar C/H and O/H values, respectively. Our simulations reproduce these measurements and show that giants like WASP-77A b should start to form beyond the CO$_2$ evaporation front, while giants like $τ$ Boötis b should originate from beyond the H$_2$O line. Our model allows the formation of sub- and super-solar atmospheric compositions. However simulations without pebble evaporation can not reproduce the super-solar C/H and O/H ratios of $τ$ Boötis b's atmosphere without additional accretion of solids. We identify the $α$ viscosity parameter of the disc as a key ingredient, because the viscosity drives the inward motion of volatile enriched vapor, responsible for the accretion of gaseous C and O. Depending on the planet's migration history order-of-magnitude differences in atmospheric C/H and O/H are expected. Our simulations also predict super-solar N/H for $τ$ Boötis b and solar N/H for WASP-77A b. We conclude that pebble evaporation is a key ingredient to explain the variety of exoplanet atmospheres, because it can explain both, sub- and super-solar atmospheric abundances.
