Cross-sections for heavy atmospheres: H<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>O self-broadening

The discovery of super-Earth and mini-Neptune exoplanets means that atmospheric signals from low-mass, temperate are being increasingly studied. signal acquired as the planet transits its host star, known transit depth, is smaller for these planets and, such, more difficult to analyze. launch space telescopes James Webb (JWST) & Ariel will give rise an explosion in quality quantity spectroscopic data available unprecedented number our galaxy. Accurately extracting information content, thereby permitting science, such data-sets require robust models techniques. We present here analysis simulated transmission spectra water-rich atmospheres, giving evidence non-negligible differences depths when self-broadening H$_2$O correctly accounted for, compared with currently typically accepted standard using H$_2$ He-broadened cross-sections. Our case-study carried out on two super-Earths, focusing water-based ranging H$_2$-rich H$_2$O-rich. depth considerably affected, increasing values by up 60 ppm, which shown be detectable JWST Ariel. most pronounced lighter (i.e. $mu$ $\sim$ 4) atmospheres. work illustrates it imperative field exoplanet spectroscopy moves toward adapted cross-sections, optimized high-mu atmospheres studies super-Earths mini-Neptunes.