超膨胀行星Kepler-79 d的无辐射红外透射谱
A Featureless Infrared Transmission Spectrum for the Super-Puff Planet Kepler-79d
摘要：
极低密度行星（“超级喷气式”）是过境行星种群中的一个小而有趣的子集。质量在超地球范围（$1-10$ M $_{\oplus}$），半径接近巨行星（$>4$ R $_{\oplus}$），它们的大包络可能已经在水雪线之外吸积，许多似乎容易发生灾难性的质量损失。水的存在和质量损失的重要性都可以使用透射光谱来探索。在这里，我们提出了新的HST WFC 3光谱和更新的开普勒过境深度测量的超级喷气开普勒-79d。我们没有检测到任何分子吸收功能的$1.1-1.7$ $μ$ m WFC 3带通和开普勒和WFC 3数据的组合是一致的，与一个平线模型，表明气溶胶在大气中的存在。我们将开普勒-79d的透射光谱的形状与微物理霾模型的预测进行了比较，该模型包含了由于持续质量损失而导致的向外粒子通量。我们发现，光化学烟雾提供了一个有吸引力的解释，观察到的性质，如开普勒-79d，因为它们同时使近红外光谱无特征，并通过移动测量的半径（光学深度单位表面在运输过程中），以降低压力，从而减少推断的包络质量损失率。我们重新审视了更广泛的问题的质量损失率的超级泡芙，发现年龄估计和质量损失率的超级泡芙大多数可以调和，如果烟雾移动光球从通常假设的压力$\sim 10$毫巴到$\sim 10 \; μ$酒吧。
英文摘要：
Extremely low density planets ('super-puffs') are a small but intriguing subset of the transiting planet population. With masses in the super-Earth range ($1-10$ M$_{\oplus}$) and radii akin to those of giant planets ($>4$ R$_{\oplus}$), their large envelopes may have been accreted beyond the water snow line and many appear to be susceptible to catastrophic mass loss. Both the presence of water and the importance of mass loss can be explored using transmission spectroscopy. Here, we present new HST WFC3 spectroscopy and updated Kepler transit depth measurements for the super-puff Kepler-79d. We do not detect any molecular absorption features in the $1.1-1.7$ $μ$m WFC3 bandpass and the combination of Kepler and WFC3 data are consistent with a flat line model, indicating the presence of aerosols in the atmosphere. We compare the shape of Kepler-79d's transmission spectrum to predictions from a microphysical haze model that incorporates an outward particle flux due to ongoing mass loss. We find that photochemical hazes offer an attractive explanation for the observed properties of super-puffs like Kepler-79d, as they simultaneously render the near-infrared spectrum featureless and reduce the inferred envelope mass loss rate by moving the measured radius (optical depth unity surface during transit) to lower pressures. We revisit the broader question of mass loss rates for super-puffs and find that the age estimates and mass loss rates for the majority of super-puffs can be reconciled if hazes move the photosphere from the typically assumed pressure of $\sim 10$ mbar to $\sim 10 \; μ$bar.
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