Line formation in the close environment of young stars

Séminaire IPAG de Benjamin Tessore (IPAG), jeudi 21 janvier 2021, 11h00, IPAG seminar room

In this talk I will present MCFOST-ART, a code dedicated to the modelling of atomic emission lines formed in the environment of stars. The code is flexible, versatile, and has been designed to work with MHD simulations considering the coupling between the gas and dust.
I will place particular emphasis on the hydrogen lines emission coming from the magnetosphere of T Tauri stars.

Radiation plays a key role in many aspects of the evolution of young stars. The modelling of the spectral signatures coming from the environment of young stars is critical to understanding the physical conditions in which they originate from.
Classical T Tauri stars are young (of a few million years old) cool and active stars presenting a strong photometric and spectroscopic variability. The interaction between the star’s magnetic field and its accretion disc (star-disc interaction) is responsible for accretion and ejection processes leading to an excess of UV radiation and the formation of emission lines. Furthermore, accretion and ejection processes have an impact on the exchange of angular momentum, a key ingredient of the evolution of solar type stars.
Most of the variability these stars show is attributed to the star-disc interaction.
The modelling of the spectral signatures coming from the environment of T Tauri stars is therefore needed to unveil the complex dynamics of this interaction, entangled in observations.
In particular, a better characterisation of the star-disc interaction is crucial to understand the evolution of nascent planetary systems, on a scale of few astronomical units.
While numerical simulations of the star-disc interaction are able to reproduce various phenomena (winds and magnetospheric accretion) the predictions of synthetic observations from state-of-the art radiative transfer models are lacking. The coupling between numerical simulations and radiative transfer calculations however offers a promising way to disentangle observations.