THE BETA PICTORIS CIRCUMSTELLAR DISK .20. SOME PHYSICAL PARAMETERS OFTHE GASEOUS COMPONENT

New high resolution spectra of beta Pictoris have been acquired in the Ca II triplet lines, arising from the 3D metastable level. In additio n to the central circumstellar component at the stellar velocity, we a lso unambiguously detected redshifted features. These variable compone nts have an unexpected intensity, relatively to the associated absorpt ion measured in the K and H lines, arising from the ground level of Ca II. In order to realize the observed fractional population [Ca II]/Ca II, a simple model of the 3D levels populating processes, including r adiative and collisional processes give some constraints on the physic al conditions in the observed gas : most of the central absorption occ urs in a confined area within 10 AU of the star, as already establishe d in Hobbs et al. (1988), but also the infalling gas reaches locally h igh electronic densities and temperatures (T-e greater than or equal t o 15 000 K and N-e > 10(6) cm(-3)).