Circumstellar gas in beta Pic

A. Vidal-Majar (1)

1 IAP - Institut d'Astrophysique de Paris

From the very early observations completed in 1984, it was clear that some gas was present in the circumstellar environment. In particular the CaII lines were showing very strong absorption signatures never observed in the local ISM toward similarly nearby stars. From the comparison of the two first observations of these lines it became also clear that these lines were time variable. This lead to numerous observational campaigns showing that stable gas as well as infalling gas was present in the system. The concept of falling and evaporating bodies (FEBs) was born: unexpectedly, exocomets were observed before exoplanets ! The lifetime of the continuously produced gas being very short, it lead to a needed additional concept of a stable braking gas at rest relative to the system and able to stop all other species through collisions. The nature of this braking gas is still debated and its location unclear. The distance of the gas is shown to be very extended, some of it being at less than 1 AU, mainly from absorption studies and some at more than 100 AU from the star, mainly from the observation of emissions signatures. The nature, origin and composition of the gas seem to be due to either the evaporation of FEBs for the closer gas or to the evaporation of distant orbiting and evaporating bodies (OEBs) of all sizes including grains, for the more remote gas.

Domaines: Planète et Univers [physics]

A. Vidal-Majar. Circumstellar gas in beta Pic. Proceedings of the conference Thirty years of beta Pic and debris disks studies. Held at Institut d'Astrophysique de Paris - France, 2014, à renseigner, Unknown Region. ⟨insu-03645311⟩