论文标题
TOI-561 B：一个低密度超短期时期的“岩石”行星，周围是金属贫困之星
TOI-561 b: A Low Density Ultra-Short Period "Rocky" Planet around a Metal-Poor Star
论文作者
论文摘要
TOI-561 is a galactic thick disk star hosting an ultra-short period (0.45 day orbit) planet with a radius of 1.37 R$_{\oplus}$, making it one of the most metal-poor ([Fe/H] = -0.41) and oldest ($\sim$10 Gyr) sites where an Earth-sized planet has been found.我们提出了来自Gemini-N/Maroon-X和Keck/Keck/Hires的新的同时径向速度测量值（RVS），我们将其与文献RVS结合使用，以得出M $ _ {B} $ = 2.24 $ = 2.24 $ \ $ \ $ 0.20 m $ _ {\ oplus} $。我们还使用了两个新的苔丝光度法来改善半径的确定，找到r $ _ {b} $ = $ 1.37 \ pm 0.04 r_ \ oplus $，并确认TOI-561 B是迄今为止测量的最低密度超级美度（$ρ_b$ = 4.8 $ = 4.8 $ 0.5 $ \ $ 0.5 g/cm）。这种密度与反映宿主恒星的铁和岩石建造元素丰度的铁岩石成分一致。但是，它也与具有挥发性包膜的低密度行星一致。行星的平衡温度（$ \ sim $ 2300 K）表明，该包膜可能由高平均分子量物种组成，例如水蒸气，二氧化碳或硅酸盐蒸气，并且可能不是原始的。我们还证明了组成的确定对恒星参数的选择很敏感，并且需要进一步的测量来确定TOI-561 B是否是一个裸露的岩石行星，一个岩石行星，具有光学上较薄的气氛的岩石行星，或者是一个罕见的典型的典范，是一个在行星上具有较小Radius小于1.5 r $ $ $ $ _ $ _} $ _ {$ oplus} $ oplus} $ _ {$ oplus} $ _ {
TOI-561 is a galactic thick disk star hosting an ultra-short period (0.45 day orbit) planet with a radius of 1.37 R$_{\oplus}$, making it one of the most metal-poor ([Fe/H] = -0.41) and oldest ($\sim$10 Gyr) sites where an Earth-sized planet has been found. We present new simultaneous radial velocity measurements (RVs) from Gemini-N/MAROON-X and Keck/HIRES, which we combined with literature RVs to derive a mass of M$_{b}$=2.24 $\pm$ 0.20 M$_{\oplus}$. We also used two new Sectors of TESS photometry to improve the radius determination, finding R$_{b}$=$1.37 \pm 0.04 R_\oplus$, and confirming that TOI-561 b is one of the lowest-density super-Earths measured to date ($ρ_b$= 4.8 $\pm$ 0.5 g/cm$^{3}$). This density is consistent with an iron-poor rocky composition reflective of the host star's iron and rock-building element abundances; however, it is also consistent with a low-density planet with a volatile envelope. The equilibrium temperature of the planet ($\sim$2300 K) suggests that this envelope would likely be composed of high mean molecular weight species, such as water vapor, carbon dioxide, or silicate vapor, and is likely not primordial. We also demonstrate that the composition determination is sensitive to the choice of stellar parameters, and that further measurements are needed to determine if TOI-561 b is a bare rocky planet, a rocky planet with an optically thin atmosphere, or a rare example of a non-primordial envelope on a planet with a radius smaller than 1.5 R$_{\oplus}$.
