论文标题
与JWST Nircam的系外行星WASP-39B的早期发行科学
Early Release Science of the exoplanet WASP-39b with JWST NIRCam
论文作者
论文摘要
测量系外行星大气中的金属性和碳与氧（C/O）比是迈出限制工作中主要的化学过程的基本步骤，如果在平衡状态下，揭示了行星形成历史。传输光谱通过限制氧气和碳种类的丰富性提供了必要的手段。但是，这需要广泛的波长覆盖范围，中等光谱分辨率和高精度，而先前的观测值则无法实现。既然JWST已经开始了科学操作，我们就可以在以前未知的波长和光谱分辨率下观察系外行星。在这里，我们报告了使用JWST的近红外摄像头（NIRCAM）报告过渡系外行星WASP-39B的时间序列观察。长波长光谱和短波长度光度光曲线跨度2.0-4.0 $μ$ m，显示最小的系统学，并在地球光谱中揭示了定义明确的分子吸收特征。具体而言，我们在大气中检测到气体H $ _2 $ O，并在ch $ _4 $的丰度上限制上限。原本突出的CO $ _2 $功能为2.8 $μ$ m，在很大程度上被H $ _2 $ o掩盖。最适合的化学平衡模型有利于1-100 $ \ times $ solar的大气金属性（即，相对于太阳的元素比氦气重的元素富集）和亚恒星碳对氧气（C/O）的比率。推断的高金属性和低C/O比可能表明在上层大气中的行星形成或不平衡过程中固体材料的显着积聚。
Measuring the metallicity and carbon-to-oxygen (C/O) ratio in exoplanet atmospheres is a fundamental step towards constraining the dominant chemical processes at work and, if in equilibrium, revealing planet formation histories. Transmission spectroscopy provides the necessary means by constraining the abundances of oxygen- and carbon-bearing species; however, this requires broad wavelength coverage, moderate spectral resolution, and high precision that, together, are not achievable with previous observatories. Now that JWST has commenced science operations, we are able to observe exoplanets at previously uncharted wavelengths and spectral resolutions. Here we report time-series observations of the transiting exoplanet WASP-39b using JWST's Near InfraRed Camera (NIRCam). The long-wavelength spectroscopic and short-wavelength photometric light curves span 2.0 - 4.0 $μ$m, exhibit minimal systematics, and reveal well-defined molecular absorption features in the planet's spectrum. Specifically, we detect gaseous H$_2$O in the atmosphere and place an upper limit on the abundance of CH$_4$. The otherwise prominent CO$_2$ feature at 2.8 $μ$m is largely masked by H$_2$O. The best-fit chemical equilibrium models favour an atmospheric metallicity of 1-100$\times$ solar (i.e., an enrichment of elements heavier than helium relative to the Sun) and a sub-stellar carbon-to-oxygen (C/O) ratio. The inferred high metallicity and low C/O ratio may indicate significant accretion of solid materials during planet formation or disequilibrium processes in the upper atmosphere.
