Characterising exoplanet atmospheres using high dispersion spectra

使用高色散光谱表征系外行星大气

• 批准号: 2285825
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2285825
• 关键词: Characterising; exoplanet; atmospheres; using; dispersion

For the last few years most common way to measure a spectrum of an exoplanets is to make a differential measurement, observing a transit (when the planet passes in front of a star) or eclipse (when the planet passes behind the star) in multiple bands, or with a low-dispersion spectrograph. An alternative approach is to use high dispersion spectroscopy, resolving individual lines in the planet's spectrum, and exploiting the orbital motion of the planet around its orbit, which shifts the planet's spectrum relative to that of the star and to the Earth's atmosphere's transmission spectrum. This method can be applied to transiting and non-transiting planets, can allow the measurement of the planet's rotation rate and even of winds in its atmosphere, and may be used in the next decade to search for biosignature molecules in the atmospheres of habitable planets orbiting low-mass stars (using extremely large, ground-based telescopes). However, the results are critically sensitive to the correction of the stellar and telluric signals. The residual spectrum is the cross-correlated with a theoretical template, which enable a detection of individual molecules but not abundance measurements. Prof Aigrain has recently developed an alternative methodology to analyse this kind of datasets, which involves modelling the star, telluric and planet signals directly, using Gaussian Process regression to model the (unknown) planet spectrum. The student will develop and apply this method to existing archival near-infrared spectra and, during the course of the PhD, to new data from (e.g.) the refurbished CRIRES+ instrument on the VLT.This project is aligned with STFC's key challenge B: How do stars and planetary systems develop and how do they support the existence of life. It will use data from STFC-supported facilities, in particular VLT/CRIRES. The work will be done in collaboration with Dr Matteo Brogi at the University of Warwick and Prof Jayne Birkby at the University of Amsterdam.

在过去的几年里，测量系外行星光谱最常见的方法是进行微分测量，在多个波段观测凌日(当行星从恒星前面经过)或日食(当行星从恒星后面经过)，或者使用低分散光谱仪。另一种方法是使用高色散光谱，解析行星光谱中的个别谱线，并利用行星围绕其轨道的轨道运动，这会使行星的光谱相对于恒星的光谱和地球大气的传输光谱发生变化。这种方法可以应用于凌日和非凌日行星，可以测量行星的自转速度，甚至可以测量其大气层中的风，并可能在未来十年内用于搜索围绕低质量恒星运行的宜居行星大气中的生物特征分子(使用极大的地面望远镜)。然而，结果对恒星和大地信号的校正极为敏感。剩余光谱是与理论模板的交叉关联，这使得能够检测单个分子，但不能测量丰度。艾格瑞恩教授最近开发了一种分析这类数据集的替代方法，包括直接对恒星、大地和行星信号进行建模，使用高斯过程回归来对(未知)行星光谱进行建模。学生将开发和应用这种方法到现有的档案近红外光谱，并在博士课程期间应用到来自(例如)的新数据。VLT上翻新的CRIRES+仪器。该项目与STFC的关键挑战B一致：恒星和行星系统是如何发展的，它们如何支持生命的存在。它将使用STFC支持的设施，特别是VLT/CRIRES的数据。这项工作将与华威大学的马泰奥·布罗吉博士和阿姆斯特丹大学的杰恩·伯克比教授合作完成。