Pushing the limits of high-angular-resolution spectroscopy, MATISSE enables us to retrieve LM-band spectra of exoplanets and brown dwarfs at small angular separations (down to 100 mas), with a medium spectral resolution of R ≈ 500. I will focus on two benchmark companions: HD 72946 B, a brown dwarf, and HR 8799 e, a directly imaged exoplanet with a low L-band flux (0.3 mJy). Observing such faint sources remains challenging, but post-processing tools have been developed to allow spectral extraction below the mJy level. My research involve also optimization and the investigation of methods improving the planet signal extraction.
The mid-IR spectral window, includes molecular features such as H2O, CH4, and CO, which help constrain or refine atmospheric parameters like the C/O ratio (formation mechanism), temperature, log(g) and vertical mixing. These physical features are indicators of the chemistry at play in their atmospheres.
In this context, we present a comparative analysis in order to better understand the physico-chemical processes shaping their atmospheres as well as their formation mechanism.