标题： 重新审视年轻AU Mic系统中凌日行星的动力学质量：在$\sim$20 Myr时AU Mic b的可能膨胀 显示英文标题

标题： Revisiting the dynamical masses of the transiting planets in the young AU Mic system: Potential AU Mic b inflation at $\sim$20 Myr

摘要： 理解行星形成在行星系统起源的一般背景以及太阳系的特定背景下非常重要，同时也用于预测在其他恒星周围发现木星、海王星和地球类似物的可能性。 我们旨在利用公开的光度和光谱数据集，精确确定围绕年轻的M型恒星AU Mic运行的凌日行星的半径和动力质量。 我们通过与高斯过程结合的联合凌日和径向速度拟合，表征年轻AU Mic系统中凌日行星的恒星活动和物理性质（半径、质量、密度）。 我们确定了最内侧凌日行星AU Mic b的半径为$R^{b}$= 4.79 +/- 0.29 R$_\oplus$，质量为$M^{b}$= 9.0 +/- 2.7 M$_\oplus$，以及整体密度为$\rho^{b}$ = 0.49 +/- 0.16 g cm$^{-3}$。 对于第二个已知的凌日行星AU Mic c，我们推断其半径为$R^{c}$= 2.79 +/- 0.18 R$_\oplus$，质量为$M^{c}$= 14.5 +/- 3.4 M$_\oplus$，并且整体密度为$\rho^{c}$= 3.90 +/- 1.17 g cm$^{-3}$。根据理论模型，AU Mic b可能拥有一个质量占比超过5%的H2包层，其中包含一定比例的岩石和水。AU Mic c可能由岩石和/或水组成，并可能拥有一个最多占其质量5%的H2大气层。AU Mic b保留了大部分的大气层，但由于强烈的恒星辐射，可能在数千万年内失去它，而AU Mic c由于距离其母星更远，可能受到的光致蒸发要少得多。 使用手头的所有数据，我们确定了AU Mic 'd' TTV候选体的3$\sigma$上质量极限为$M^{[d]}\sin{i}$ = 8.6 M$_{\oplus}$。 此外，我们未确认最近提出的轨道周期为33.4天的行星候选体AU Mic 'e' 的存在。 显示英文摘要

摘要： Understanding planet formation is important in the context of the origin of planetary systems in general and of the Solar System in particular, as well as to predict the likelihood of finding Jupiter, Neptune, and Earth analogues around other stars. We aim to precisely determine the radii and dynamical masses of transiting planets orbiting the young M star AU Mic using public photometric and spectroscopic datasets. We characterise the stellar activity and physical properties (radius, mass, density) of the transiting planets in the young AU Mic system through joint transit and radial velocity fits with Gaussian processes. We determine a radius of $R^{b}$= 4.79 +/- 0.29 R$_\oplus$, a mass of $M^{b}$= 9.0 +/- 2.7 M$_\oplus$, and a bulk density of $\rho^{b}$ = 0.49 +/- 0.16 g cm$^{-3}$ for the innermost transiting planet AU Mic b. For the second known transiting planet, AU Mic c, we infer a radius of $R^{c}$= 2.79 +/- 0.18 R$_\oplus$, a mass of $M^{c}$= 14.5 +/- 3.4 M$_\oplus$, and a bulk density of $\rho^{c}$ = 3.90 +/- 1.17 g cm$^{-3}$. According to theoretical models, AU Mic b may harbour an H2 envelope larger than 5\% by mass, with a fraction of rock and a fraction of water. AU Mic c could be made of rock and/or water and may have an H2 atmosphere comprising at most 5\% of its mass. AU Mic b has retained most of its atmosphere but might lose it over tens of millions of years due to the strong stellar radiation, while AU Mic c likely suffers much less photo-evaporation because it lies at a larger separation from its host. Using all the datasets in hand, we determine a 3$\sigma$ upper mass limit of $M^{[d]}\sin{i}$ = 8.6 M$_{\oplus}$ for the AU Mic 'd' TTV-candidate. In addition, we do not confirm the recently proposed existence of the planet candidate AU Mic 'e' with an orbital period of 33.4 days.