Comparing transit spectroscopy pipelines at the catalogue level: evidence for systematic differences

The fidelity of data reduction pipelines significantly influences the interpretation of exoplanetary data. As we approach the operational phases of the James Webb Space Telescope (JWST) and the ARIEL space mission, addressing pipeline-induced variances is imperative due to its profound implications on our understanding of exoplanets. Our study is pioneering in its comparative analysis of pipeline results at a catalogue level, employing a robust framework to statistically evaluate outcomes from the Hubble Space Telescope’s Wide Field Camera 3 across three independent pipelines: Iraclis, EXCALIBUR, and CASCADe.

Despite utilising identical data, substantial differences in extracted spectra and planetary parameters were observed. Notably, variations in detected atmospheric compositions, particularly in water and methane content, and radius and temperature estimation, exemplify significant pipeline-induced biases. These discrepancies manifest most starkly in compositional trends across the exoplanet catalogues, potentially skewing class-wide analyses and misleading interpretations of atmospheric conditions.

This study highlights the urgent need for the exoplanetary science community to standardise data reduction techniques to harness the full potential of future observations. The outcome of our work is vital not only for the academic community but also for upcoming space missions, ensuring that interpretations of exoplanetary atmospheres are based on the most accurate data possible.