用神经网络去除系外行星光谱中的恒星干扰和噪声,提升大气参数反演精度。
Efficient reduction of stellar contamination and noise in planetary transmission spectra using neural networks
- 采用去噪自编码器(DAE)从光谱中自动分离并修复恒星污染与仪器噪声。
- 在低信噪比下仍能保留关键分子特征,反演结果与传统方法相当但速度更快。
- 计算成本降低约90%,适合大规模系外行星大气研究,尤其适用于岩石与亚海王星类行星。
系外行星大气的表征因詹姆斯·韦布空间望远镜(JWST)的红外灵敏度而取得突破,其高精度使传输光谱学成为可能。然而,恒星非均质性(如黑子和亮斑)仍是主要干扰源,若未妥善校正,会偏差大气反演结果。本文提出一种基于神经网络的方法,特别是去噪自编码器(Denoising AutoEncoders, DAEs),用于减少系外行星传输光谱中的恒星污染和仪器噪声。我们使用大量合成数据训练了针对类地行星(TRAPPIST-1e 类似物)和亚海王星(K2-18b 类似物)的DAE模型,并在受污染光谱上进行大气反演实验,对比深度学习方法与标准校正技术的准确性和计算开销。结果显示,该方法能有效重建无污染光谱,在低信噪比条件下仍保留关键分子特征;反演测试表明,经DAE预处理后的参数估计与同步拟合恒星污染的方法基本一致,但计算成本降低约一个数量级。这证明了DAEs在保持高精度的同时显著提升效率,为未来岩石与亚海王星类系外行星的大气表征流程提供了可行方案。
原文摘要 · Abstract (English)
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.
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