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arXiv 2110.09080astro-ph.EP
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走向多dimensional analysis的透射光谱学。部分II:从高温到超高温检索中的昼夜诱导偏倚

Towards multi-dimensional analysis of transmission spectroscopy. Part II: Day-night induced biases in retrievals from hot to ultra-hot Jupiters

William Pluriel, Jeremy Leconte, Vivien Parmentier, Tiziano Zingales, Aurelien Falco, Franck Selsis, Pascal Borde

摘要:

热散射是透射光谱分析的很好的目标。它们的大气层高度很高,这意味着高信噪比。由于这些行星的轨道靠近它们的恒星,它们的大气层在白天和黑夜之间经常呈现出强烈的热和化学不均匀性。对于最热的行星,其大气层中发生了几种物质的热分解,导致两个半球之间的化学二分法更强。它已经被证明,目前的检索算法,这是使用1D前向模型,发现有偏见的分子丰度在超热蒸发器。在这里,我们量化了这些偏差存在的有效温度域。我们使用了一组12个典型的热彗星的模拟从Teq = 1000 K到Teq = 2100 K进行了亚恒星和行星大气辐射和环流全球气候模型,并产生透射光谱,充分考虑了大气的三维结构与Pytmoclave 3R。然后使用1D TauREx检索代码分析这些光谱。我们发现,JWST类数据,占非等温的垂直温度分布需要在整个温度范围内。我们进一步发现,1D检索代码开始估计错误的参数值的平衡温度大于1400 K的行星,如果有吸收剂在可见光能够创建一个热平流层。在低压下的高温确实需要物种的热解离,这产生了强烈的化学昼夜二分法。作为一个副产品,我们证明,当使用合成观测使用贝叶斯框架来评估给定特征或过程的可检测性时,只要正确考虑预期的观测不确定性,使用非随机输入数据是有效的。

英文摘要:

Hot Jupiters are very good targets for transmission spectroscopy analysis. Their atmospheres have a large scale height implying a high signal to noise ratio. As these planets orbit close to their stars, they often present strong thermal and chemical hetereogeneities between the day and the night side of their atmosphere. For the hottest ones, the thermal dissociation of several species occurs in their atmospheres which leads to a stronger chemical dichotomy between the two hemispheres. It has already been shown that the current retrieval algorithms, which are using 1D forward models, find biased molecular abundances in ultra hot Jupiters. Here, we quantify the effective temperature domain over which these biases are present. We use a set of 12 simulations of typical Hot Jupiters from Teq = 1000 K to Teq = 2100 K performed with the Substellar and Planetary Atmospheric Radiation and Circulation global climate model and generate transmission spectra that fully account for the 3D structure of the atmosphere with Pytmosph3R. These spectra are then analyzed using the 1D TauREx retrieval code. We find that for JWST-like data, accounting for non-isothermal vertical temperature profiles is required over the whole temperature range. We further find that 1D retrieval codes start to estimate wrong parameter values for planets with equilibrium temperatures greater than 1400 K if there are absorbers in the visible able to create a hot stratosphere. The high temperatures at low pressures indeed entail a thermal dissociation of species which creates a strong chemical day-night dichotomy. As a by-product, we demonstrate that when using synthetic observations to assess the detectability of a given feature or process using a Bayesian framework, it is valid to use non-randomized input data, as long as the anticipated observational uncertainties are correctly taken into account.

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