The characterization of exoplanetary atmospheres has been transformed by the James Webb Space Telescope (JWST), whose infrared sensitivity enables transmission spectroscopy at unprecedented precision. However, stellar heterogeneities (e.g., spots and faculae) remain a dominant source of contamination that can bias atmospheric retrievals if not properly corrected. We present a methodology for reducing stellar contamination and instrument-specific noise from exoplanet transmission spectra using neural networks, in particular the so-called Denoising AutoEncoders (DAEs). Our goals are to enable fast, accurate corrections that improve the reliability of atmospheric parameter retrievals and to promote the use of unsupervised algorithms for efficient data processing. We designed and trained DAE architectures using large synthetic datasets of terrestrial (TRAPPIST-1e analogues) and sub-Neptune (K2-18b analogues) planets. Atmospheric retrieval experiments were then performed on contaminated spectra in order to compare our deep-learning approach against standard correction methods in terms of accuracy and computational cost. Our autoencoders successfully reconstruct uncontaminated spectra, preserving essential molecular features even in low-S/N regimes. In retrieval tests, the denoising autoencoder pre-processing yields atmospheric parameter estimates broadly comparable to those obtained with simultaneous stellar-contamination fitting. Notably, our method maintains a much lower computational cost, approximately one order of magnitude smaller. These results demonstrate that DAEs outperform conventional correction methods in computational efficiency while maintaining high accuracy, paving the way for their integration into future atmospheric characterization pipelines for both rocky and sub-Neptune exoplanets.
Evidence for stellar contamination and water absorption in NGTS-5b's transmission spectra with GTC/OSIRIS
CAS Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences(中国科学院行星科学重点实验室,紫金山天文台);University of Science and Technology of China(中国科学技术大学);Instituto de Astrofísica de Canarias (IAC)(加那利天体物理学研究所);Universidad de La Laguna (ULL)(拉各拉纳大学)
Where does the simplified Stellar Contamination Model fail in Exoplanet Transmission Spectroscopy?
Jet Propulsion Laboratory, California Institute of Technology(加州理工学院喷气推进实验室);Center for Radio Astronomy and Astrophysics Mackenzie (CRAAM), Mackenzie Presbyterian University(麦肯锡长老会大学射电天体物理学中心)
Two Potential Exoplanets around A-type Stars Selected from 18 Planetary Candidates
Yunnan Observatories, Chinese Academy of Sciences (CAS)(中国科学院云南天文台);University of Chinese Academy of Sciences(中国科学院大学);School of Physics and Astronomy, Yunnan University(云南大学物理与天文学院)
A theory of transmission spectroscopy of hydrodynamic outflows from planetary atmospheres: Spectral-line saturation and limits on mass-loss constraints
Instituto de Astrofísica de Andalucía (IAA-CSIC)(安达卢西亚天体物理研究所)
The Featureless HST/WFC3 Transmission Spectrum of the Rocky Exoplanet GJ 1132b: No Evidence For A Cloud-Free Primordial Atmosphere and Constraints on Starspot Contamination
围绕着一颗距离12 pc的M矮星运行的凌日系外行星GJ 1132 b是透射光谱学的主要目标。GJ 1132 b的质量是地球质量的1.7倍,半径是地球半径的1.1倍,其体积密度表明这颗行星是岩石行星。然而,在580 K的平衡温度下,GJ 1132 b可能仍然保留了一些大气层的外观。了解这种大气层是否存在及其组成对于了解绕M矮星运行的类地行星的大气层如何演变至关重要。利用哈勃空间望远镜(HST)的WFC 3(Wide Field Camera 3)观测了GJ 1132 b的5次凌日。我们发现了一个从1.1- 1.7微米的无特征的透射光谱,排除了无云的大气与金属度<300x Solar with >4.8 $σ$的信心。我们将WFC 3的结果与TESS和档案宽带和光谱观测的过境深度相结合,找到了0.7- 4.5微米的无特征光谱。GJ 1132 b有高平均分子量的大气,拥有高空气溶胶层,或实际上没有大气。需要更高精度的观测来区分这些可能性。我们探讨了热和冷的恒星黑子对观测到的透射光谱GJ 1132 b的影响,量化了斑点引起的过境深度特征的幅度。使用一个简单的泊松模型,我们估计点的温度对比度,点覆盖率,和点的大小为GJ 1132。这些限制,以及建模框架,可能是有用的GJ 1132 b或其他行星过境类似的不活跃的M矮星的未来观测。
GEMS JWST: Transmission spectroscopy of TOI-5205b reveals significant stellar contamination and a metal-poor atmosphere
NASA Goddard Space Flight Center(美国宇航局戈达德太空飞行中心);Johns Hopkins APL(约翰斯·霍普金斯大学应用物理实验室);University of California, Riverside(加州大学河滨分校);University of Zürich(苏黎世大学);Carnegie Science(卡内基科学研究所)
The Effect of Stellar Contamination on Low-resolution Transmission Spectroscopy: Needs Identified by NASA's Exoplanet Exploration Program Study Analysis Group 21
Correcting the effect of stellar spots on ARIEL transmission spectra II.The limb darkening effect
这篇论文是修正围绕活跃恒星运行的凌日行星的透射光谱的努力的一部分。在论文I(Cracchiolo et al. 2020)中,我们已经证明了一种方法,可以最大限度地减少透射光谱上未被遮蔽的星点引起的潜在偏差,假设一个由填充因子和温度参数化的星点模型。在这项工作中,我们介绍了临边暗化效应,因此,在恒星盘中的位置和过境行星的碰撞参量现在起着关键作用。在ARIEL分辨率下,对三种有代表性的行星系的凌日过程进行了数值模拟。我们发现,一个现实的治疗的肢体变暗需要可靠地估计两个点的参数和过境行星的透射光谱。此外,我们表明,点onthe检索的行星透射光谱的影响是显着的斑点靠近恒星的中心,覆盖一个分数大于0.05,温度对比度大于500 K,对于这些情况,我们的方法可以自信地提取出掩星和非掩星情况下过境行星的透射光谱和碰撞参量掩星点,只要我们有一个准确的恒星参数和仪器性能的可靠模拟器的特性。
Transmission photometry of WASP-12b: simultaneous measurement of the planetary radius in three bands
在地面和太空中,透射光谱学已经成功地用于探测过境系外行星的大气层。这种技术在地面上是具有挑战性的,因为地面摄谱仪往往没有被设计成光度稳定的,并且诸如可变狭缝损耗之类的影响会导致显著的系统不确定性。另一种方法是在多个波段同时进行光度观测,以确定与波长相关的过境深度差。我们报告的应用程序,这种技术的一个最热的已知系外行星,WASP-12 b,使用三光束相机ULTRACAM。我们在Sloan u '和两个中心在4169和6010埃的窄带滤光片中获得了同时的光变曲线,其半高宽分别为52和118埃。我们用光度模型拟合这些光变曲线,并确定三个不同波段的行星半径。我们的数据显示,没有证据表明在我们研究的波长范围内行星半径的差异,并与大气,这是由瑞利散射从高海拔的阴霾,以及更复杂的大气模型,其中包括分子,如TiO的影响占主导地位。我们的行星半径测量的平均精度为2.6%,相比之下,模型在这个波长范围内预测的半径差异为1.4%-2.4%。我们还发现在我们的三个波段的入口和出口的一致的时间,在早期的入口,这已被报告为该系统在较短的波长。
The capability of CSST in characterizing planetary atmospheres. I. transmission spectroscopy of hot Jupiters
National Astronomical Observatories, Chinese Academy of Sciences(中国科学院国家天文台);School of Astronomy and Space Science, University of Chinese Academy of Sciences(中国科学院大学天文与空间科学学院);Department of Astronomy, University of Science and Technology of China(中国科学技术大学天文系);Deep Space Exploration Laboratory, Hefei, Anhui(深空探测实验室);CAS Key Laboratory of Planetary Science, Purple Mountain Observatory, Chinese Academy of Sciences(中国科学院紫金山天文台行星科学重点实验室);Institute of Science and Technology for Deep Space Exploration, Nanjing University(南京大学深空探测研究院)
A Panchromatic Characterization of the Evening and Morning Atmosphere of WASP-107 b: Composition and Cloud Variations, and Insight into the Effect of Stellar Contamination
本研究利用 JWST 全部仪器重新分析 WASP-107 b 的临边透射光谱,确认黄昏-黎明温度差异,发现 SO₂、CO₂ 及云层分布不对称,并揭示星斑污染对临边测量的偏差及校正方法。
Precise measurement of WASP-31 b's Rossiter-McLaughlin effect and characterization of the planet transmission spectra
Observatoire de l’Université de Genève(日内瓦大学天文台);Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto(波尔图大学空间与天体物理研究所);Département de Physique, Institut Trottier de Recherche sur les Exoplanètes, Université de Montréal(蒙特利尔大学特罗蒂埃系外行星研究系);INAF(意大利国家天体物理研究所)
NASA's Pandora SmallSat Mission: Simulating the Impact of Stellar Photospheric Heterogeneity and Its Correction
Massachusetts Institute of Technology(麻省理工学院);NASA Goddard Space Flight Center(NASA戈达德太空飞行中心);The University of Arizona(亚利桑那大学);Lawrence Livermore National Laboratory(劳伦斯利弗莫尔国家实验室);Arizona State University(亚利桑那州立大学)