使用喜马拉雅钱德拉望远镜上的HFOSC对差分透射光谱学中的系统误差的观测研究
An Observational Study of Systematics in Differential Transmission Spectroscopy Using HFOSC on the Himalayan Chandra Telescope
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中文总结 AI 辅助
本研究以HAT-P-1 b、WASP-33 b、WASP-12 b为目标，利用HCT的HFOSC研究差分透射光谱学的系统误差，发现其可能与视场畸变和仪器挠曲相关，凸显了减小地基系外行星透射光谱学系统误差的重要性。
中文摘要 AI 辅助
地基低分辨率透射光谱学需要达到百万分之几百的测光精度，因此对仪器和大气系统误差十分敏感。本研究使用2米口径喜马拉雅钱德拉望远镜（HCT）上的Hanle暗天体摄谱仪相机（HFOSC），研究影响差分透射光谱学的系统效应。该研究的动机来自HAT-P-1 b的白光曲线中观测到的额外流量下降。HAT-P-1 b是差分分光光度测量的理想目标，因为它拥有一颗亮度相近、间距合适的目视双星伴星，可作为参考星。为探究该特征的起源，我们分析了多个观测参数，包括半高全宽（FWHM）变化、光谱迹线运动、质心漂移和光谱位移。我们还以无狭缝模式观测了WASP-33 b，以测试差分狭缝损失是否能解释观测到的系统误差。此外，对WASP-12 b的观测被用于通过共模校正推导宽带光学透射光谱。该额外流量下降不太可能仅由差分狭缝损失导致，因为在有狭缝和无狭缝观测中均存在相似的差分质心和光谱位移。结果表明，观测到的系统误差可能与视场相关的畸变和指向相关的仪器挠曲有关，尽管其确切原因仍未知。总体而言，本研究强调了在地基系外行星透射光谱学中理解和减小观测系统误差的重要性，尤其是对于需要百万分之几百测光精度的测量而言。
英文摘要
Ground-based low-resolution transmission spectroscopy requires photometric precision of a few hundred parts per million, making it sensitive to instrumental and atmospheric systematics. This work studies the systematic effects affecting differential transmission spectroscopy using the Hanle Faint Object Spectrograph Camera (HFOSC) on the 2-m Himalayan Chandra Telescope (HCT). The study was motivated by an additional flux drop observed in the white-light curve of HAT-P-1 b. HAT-P-1 b is an ideal target for differential spectrophotometry because it has a visual binary companion with similar brightness at a suitable separation, allowing the companion star to be used as a reference. To investigate the origin of this feature, we analyzed several observational parameters, including FWHM variations, spectral trace motion, centroid drift, and spectral shifts. We also observed WASP-33 b in slitless mode to test whether differential slit losses could explain the observed systematic. In addition, observations of WASP-12 b were used to derive a broadband optical transmission spectrum using common-mode correction. The additional flux drop is unlikely to be caused only by differential slit losses, since similar differential centroid and spectral shifts are present in both slit and slitless observations. The results suggest that the observed systematic may be related to field-dependent distortions and pointing-dependent instrumental flexure, although its exact cause is still unknown. Overall, this work highlights the importance of understanding and reducing observational systematics in ground-based exoplanet transmission spectroscopy, especially for measurements that require photometric precision of a few hundred parts per million.
