A Comparison of Simulated JWST Observations Derived from Equilibrium and Non-equilibrium Chemistry Models of Giant Exoplanets
A Comparison of Simulated JWST Observations Derived from Equilibrium and Non-equilibrium Chemistry Models of Giant Exoplanets
复制标题
由巨型系外行星平衡和非平衡化学模型得出的 JWST 模拟观测结果的比较
DOI：
10.3847/1538-4357/aa9e51
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
H. Wakeford
中科院分区：
文献类型：
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作者：
S. Blumenthal;A. Mandell;E. H'ebrard;N. Batalha;P. Cubillos;S. Rugheimer;H. Wakeford
我们的目标是通过詹姆斯·韦伯太空望远镜（JWST）在凌日行星的大气中观察到平衡化学和不平衡化学之间的差异。我们对三颗行星（HD 189733b、WASP-80b和GJ 436b）在两种金属丰度下处于化学平衡和非化学平衡状态的日侧发射光谱进行了案例研究。之所以选择这三颗行星，是因为它们的行星质量和平衡温度范围很大，从炎热的木星大小到温暖的海王星大小。我们将Venot etal .（2012）的一维不平衡化学模型（其中考虑了热化学动力学、垂直输运和光化学）与专门为热木星开发的一维伪逐行辐射传输模型Pyrat bay联系起来，然后使用PandExo模拟JWST光谱，比较温度、金属量和半径的影响。我们发现，由于CO和CO2丰度的不平衡，在4到5 μm之间的差异最为显著，在某些情况下，H2O也是如此。我们的案例研究显示了行星质量、温度和金属丰度的某个“最佳点”，在这里平衡和不平衡之间的差异是可以观察到的。对于类似WASP-80b的行星，JWST的NIRSpec G395M可以通过一次日食事件检测到由于不平衡化学反应而产生的差异。对于一颗类似于GJ 436b的行星，由于不平衡化学的可观测性在低金属丰度的情况下是可能的，但在高金属丰度的情况下是不可能的。
We aim to see if the difference between equilibrium and disequilibrium chemistry is observable in the atmospheres of transiting planets by the James Webb Space Telescope (JWST). We perform a case study comparing the dayside emission spectra of three planets like HD 189733b, WASP-80b, and GJ 436b, in and out of chemical equilibrium at two metallicities each. These three planets were chosen because they span a large range of planetary masses and equilibrium temperatures, from hot and Jupiter-sized to warm and Neptune-sized. We link the one-dimensional disequilibrium chemistry model from Venot et al. (2012), in which thermochemical kinetics, vertical transport, and photochemistry are taken into account, to the one-dimensional, pseudo line-by-line radiative transfer model, Pyrat bay, developed especially for hot Jupiters, and then simulate JWST spectra using PandExo for comparing the effects of temperature, metallicity, and radius. We find the most significant differences from 4 to 5 μm due to disequilibrium from CO and CO2 abundances, and also H2O for select cases. Our case study shows a certain “sweet spot” of planetary mass, temperature, and metallicity where the difference between equilibrium and disequilibrium is observable. For a planet similar to WASP-80b, JWST’s NIRSpec G395M can detect differences due to disequilibrium chemistry with one eclipse event. For a planet similar to GJ 436b, the observability of differences due to disequilibrium chemistry is possible at low metallicity given five eclipse events, but not possible at the higher metallicity.