| Name: | Lokesh Manickavasaham |
| Affiliation: | Indian Institute of Technology Kharagpur |
| Conference ID: | ASI2025_397 |
| Title: | Addressing Wavelength-Correlated Systematics in Exoplanet Transmission Spectroscopy: A 2D Gaussian Process Approach |
| Authors: | Lokesh Manickavasaham 1, Manjunath Bestha 2, Sivarani Thirupathi 2 |
| Authors Affiliation: | 1 Indian Institute of Technology Kharagpur, Kharagpur - 721302, India
2 Indian Institute of Astrophysics, Bangalore - 560034, India
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| Mode of Presentation: | Poster |
| Abstract Category: | Sun, Solar System, Exoplanets, and Astrobiology |
| Abstract: | Ground-based transmission spectroscopy is often dominated by systematics, obstructing us from leveraging the advantages of larger aperture sizes compared to space-based observations. These systematics could be time-correlated, uniform across all spectroscopic light curves, or wavelength-correlated, which could significantly affect the characterization of exoplanet atmospheres. Gaussian Processes (GPs) were introduced in transmission spectroscopy by Gibson et al. (2012) to model correlated systematics in a non-parametric way. The technique uses auxiliary information about the observation and independently fits each spectroscopic light curve to provide robust atmospheric retrievals. However, this method assumes that the uncertainties in the transmission spectrum are uncorrelated in wavelength, which can cause discrepancies and degrade the precision of atmospheric retrievals. To address this limitation, we explore a 2D GP framework to model both time- and wavelength-correlated systematics. By combining the spectroscopic light curves to create a 2D grid, the GP simultaneously fits for the transit depth with the hyperparameters shared across wavelengths. While this method is computationally intensive, it recovers the full covariance matrix of the transmission spectrum and improves the accuracy of atmospheric retrievals. It can potentially eliminate the need for ‘common-mode’ correction, which produces an offset in the transmission spectrum. We present the detailed framework and its application to ground-based observations, including those obtained from the 2m Himalayan Chandra Telescope (HCT). As we move towards detecting smaller and cooler planets, developing new methods to address complex systematics becomes increasingly essential. |
