Background - The study of exoplanets atmospheres is one of the most intriguing challenges in exoplanet field nowadays and the High Resolution Spectroscopy (HRS) has recently emerged as one of the leading methods for detecting atomic and molecular species in their atmospheres.
Nevertheless extraordinary results have been achieved (Birkby, 2018), High Resolution Spectroscopy alone is not enough. 1D models of the host star have been coupled to HRS observations, but they do not reproduce the complexity of stellar convection mechanism (Chiavassa & Brogi, 2019). On the contrary, 3D Radiative Hydrodynamical (3D RHD) simulations take it into account intrinsically, allowing us to correctly reproduce asymmetric and blue-shifted spectral lines due to the granulation pattern of the stellar disk, which is a very important source of uncertainties (Chiavassa et al. 2017). However, numerical simulations have been computed independently for star and planet so far, while the acquired spectrum contains both the signals. For instance, some molecular species (e.g, CO) form in the same region of the spectrum, thus planetary and stellar spectral lines are completely mixed and overlapped.
A next step forward is needed: computing stellar and planetary models together during the planet transit.
Goal - With my work, I aim at upgrading the already-in-place 3D radiative transfer code Optim3D (Chiavassa et al. 2009) — largely used for stellar purposes so far — to take into account also the exoplanetary contribution and finally carry out a full characterisation of planets and their host stars.
I will present the advantages of the simultaneous use of 3D RHD stellar simulations and exoplanet’s Global Climate Models (GCMs) in generating unprecedented precise synthetic spectra and mimicking the observation at high resolving power during the planet transit.
This work is that step forward.
We will be able to compute a complete dynamic characterisation: on one side, a precise knowledge of the stellar dynamic (i.e. convection-related surface structures) would allow to extract unequivocally the planetary signal; on the other one, a well-modelled dynamic of the planet (i.e. depth, shape, and position of spectral lines) would provide us with considerable information about the planetary atmospheric circulation.