论文标题
海王星沙漠中的超热海王星
An Ultra-Hot Neptune in the Neptune desert
论文作者
论文摘要
在200个类似太阳的恒星中，大约有一个行星短于一天的轨道时期：超短暂的周期行星（Sanchis-Ojeda等人，2014年； Winn等人，2018年）。所有先前已知的超短期阶段行星都是热木星，尺寸高于10地球半径（RE），或者显然是小于2 Re的岩石行星。这种缺乏中间大小的行星（“热海王星沙漠”）被解释为低质量行星无法在面对强烈的恒星照射下保留任何氢/氦（H/HE）信封。在这里，我们报告了一个超短距离的星球，半径为4.6 RE，质量为29 me，牢固地在热海王星沙漠中。来自过渡系外行星调查卫星的数据（Ricker等人，2015年）显示，每0.79天，明亮的阳光恒星\ starname \ transits的过渡。行星的平均密度与海王星的平均密度相似，根据热进化模型，它具有构成9.0^（+2.7）_（ - 2.9）％总质量的富含h/he He的包膜。在2000 K左右的平衡温度下，目前尚不清楚这种“超热海王星”如何设法保留这样的信封。恒星的亮度将促进对地球大气的后续观察，以更好地了解其起源和物理性质（VMAG = 9.8）。
About one out of 200 Sun-like stars has a planet with an orbital period shorter than one day: an ultra-short-period planet (Sanchis-ojeda et al. 2014; Winn et al. 2018). All of the previously known ultra-short-period planets are either hot Jupiters, with sizes above 10 Earth radii (Re), or apparently rocky planets smaller than 2 Re. Such lack of planets of intermediate size (the "hot Neptune desert") has been interpreted as the inability of low-mass planets to retain any hydrogen/helium (H/He) envelope in the face of strong stellar irradiation. Here, we report the discovery of an ultra-short-period planet with a radius of 4.6 Re and a mass of 29 Me, firmly in the hot Neptune desert. Data from the Transiting Exoplanet Survey Satellite (Ricker et al. 2015) revealed transits of the bright Sun-like star \starname\, every 0.79 days. The planet's mean density is similar to that of Neptune, and according to thermal evolution models, it has a H/He-rich envelope constituting 9.0^(+2.7)_(-2.9)% of the total mass. With an equilibrium temperature around 2000 K, it is unclear how this "ultra-hot Neptune" managed to retain such an envelope. Follow-up observations of the planet's atmosphere to better understand its origin and physical nature will be facilitated by the star's brightness (Vmag=9.8).
