Comparative detection and robustness analysis of CO₂ absorption features in WASP-39b using multi-instrument JWST ERS data

Abstract

The James Webb Space Telescope (JWST) Early Release Science (ERS) program has delivered high-precision transmission spectra of the hot Saturn-mass exoplanet WASP-39b, enabling the first unambiguous detection of carbon dioxide (CO₂) in an exoplanet atmosphere. In this work, we perform an independent, model-independent reanalysis of publicly available JWST ERS transmission spectra from NIRSpec PRISM, reduced using multiple independent data reduction pipelines, to assess the robustness and reproducibility of the CO₂ detection. Using published transmission spectra from NIRSpec PRISM and reductions produced by the TSHIRT, TIBERIUS, FIREFLY, and EUREKA pipelines, we conduct a comparative analysis of the CO₂ absorption feature near 4.3 μm. Band-integrated absorption depths and bootstrap-based confidence intervals are computed using a consistent statistical framework to assess the internal robustness of the CO₂ feature. All pipelines yield a strong and consistent CO₂ detection, confirming the robustness of the feature. However, measurable differences in absorption depth and uncertainty are observed between pipelines, indicating the presence of reduction-induced systematics that affect quantitative measurements. This study reinforces confidence in the JWST CO₂ detection while highlighting the importance of cross-pipeline validation for precise atmospheric characterization.