气态贫乏行星形成发生在围绕红矮星LHS 1903的四行星系统中
Gas-depleted planet formation occurred in the four-planet system around the red dwarf LHS 1903
AI总结：
研究发现LHS 1903系统中存在四颗行星，其中三颗具有扩展大气层，而最远的行星LHS 1903 e由气态贫乏物质形成，揭示了气态贫乏行星形成的机制。
摘要：
小系外行星半径显示两种群体，称为超级地球和亚海王星，被称为半径谷的间隙所分隔。这可能是由于恒星或内部加热导致大气层的去除，或初始大气层的缺乏所产生。我们利用凌星光度测量和径向速度测量来检测和表征围绕银河系厚盘中的红矮星LHS 1903运行的四颗行星。这些行星的轨道周期在2.2至29.3天之间，并且在一个行星系统内跨越了半径谷。推导出的密度表明，LHS 1903 b是岩石状的，而LHS 1903 c和LHS 1903 d具有扩展的大气层。尽管最远离宿主恒星的行星LHS 1903 e没有气态包层，表明它是由气态贫乏的物质形成的。
英文摘要：
Small exoplanet radii show two populations, referred to as super-Earths and sub-Neptunes, separated by a gap known as the radius valley. This may be produced by the removal of atmospheres due to stellar or internal heating, or lack of an initial envelope. We us transit photometry and radial velocity measurements to detect and characterize four planets orbiting LHS 1903, a red dwarf (M-dwarf) star in the Milky Way's thick disk. The planets have orbital periods between 2.2 and 29.3 days, and span the radius valley within a single planetary system. The derived densities indicate that LHS 1903 b is rocky, while LHS 1903 c and LHS 1903 d have extended atmospheres. Although the most distant planet from the host star, LHS 1903 e, has no gaseous envelope, indicating it formed from gas-depleted material.
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