论文标题
大气检索高精度棕色矮人光谱的考虑因素
Considerations for Atmospheric Retrieval of High-Precision Brown Dwarf Spectra
论文作者
论文摘要
孤立的棕色矮人提供了出色的实验室,以了解低辐射状态中的大气物理学,并且可以比外部球星更精确地观察到。因此,它们可以瞥见外部行星的高SNR观察的未来。在这项工作中,我们研究了一些新的考虑因素,这些因素对于亚固有物体的高质量热发射光谱的大气检索很重要。我们使用Hydra大气检索代码的改编来实现这一目标。我们提出了由多个大气层组成的棕色矮人的参数压力温度(P-T)曲线,该层由每一层的温度变化参数。该模型允许准确检索棕色矮人大气的陡峭温度梯度,同时避免通常遇到的数值人工制品。 P-T模型在Photosphere中特别灵活,Thephere可以到达几十杆的小栏。我们展示了一种方法,将模型不确定性包括在检索中,重点是用于检索的大气模型中有限光谱和垂直分辨率引入的不确定性(在本案中〜8 \%)。我们通过将其应用于模拟数据集来验证我们的检索框架,然后将其应用于T-DWARF 2MASS J2339+1352的HST/WFC3频谱。我们以〜0.1 dex的精度检索物体中H2O和CH4的亚晶状体丰度。此外,我们将温度结构限制为光球中〜100 k以内。我们的结果证明了高SNR光谱的希望提供了子遗嘱对象的高精度丰度估计。
Isolated brown dwarfs provide remarkable laboratories for understanding atmospheric physics in the low-irradiation regime, and can be observed more precisely than exoplanets. As such, they provide a glimpse into the future of high-SNR observations of exoplanets. In this work, we investigate several new considerations that are important for atmospheric retrievals of high-quality thermal emission spectra of sub-stellar objects. We pursue this using an adaptation of the HyDRA atmospheric retrieval code. We propose a parametric pressure-temperature (P-T) profile for brown dwarfs consisting of multiple atmospheric layers, parameterised by the temperature change across each layer. This model allows the steep temperature gradient of brown dwarf atmospheres to be accurately retrieved while avoiding commonly-encountered numerical artefacts. The P-T model is especially flexible in the photosphere, which can reach a few tens of bar for T-dwarfs. We demonstrate an approach to include model uncertainties in the retrieval, focusing on uncertainties introduced by finite spectral and vertical resolution in the atmospheric model used for retrieval (~8\% in the present case). We validate our retrieval framework by applying it to a simulated data set and then apply it to the HST/WFC3 spectrum of the T-dwarf 2MASS J2339+1352. We retrieve sub-solar abundances of H2O and CH4 in the object at ~0.1 dex precision. Additionally, we constrain the temperature structure to within ~100 K in the photosphere. Our results demonstrate the promise of high-SNR spectra to provide high-precision abundance estimates of sub-stellar objects.