THE BETA-PICTORIS CIRCUMSTELLAR DISK .17. PHYSICAL AND CHEMICAL-PARAMETERS OF THE DISK

New high resolution spectroscopic observations in the visible as well as archival HST UV data are used to investigate some physical and chem ical properties of the disk around beta Pictoris. A number of circumst ellar lines are detected for the first time: Fe I, as well as weak lin es of Fe II, Mn II and Zn II. Reliable estimates of the total gaseous abundance of Fe I, Fe II, Zn II and Mn II are given for the stable par t of the gaseous disk, enabling to investigate its chemical compositio n. The various observed metallic abundances are found to be close to s olar ones, which may indicate that evaporation processes of refractory or cometary bodies occur to produce this gas. These observations also enable to derive other important information for the gaseous disk: th e electronic densities range between 10(3) and 10(6) cm(-3); the total Hydrogen density column is 1-2 10(19) cm(-2), assuming that volatiles in the gaseous disk have solar system abundances; assuming that the h ydrogen depletion is similar to the cometary ones would reduce the est imated column density by a factor of 10(3) to 10(4). Tentative estimat es of the abundance of some refractory elements in the gas phase durin g two variable events are also given. In these two cases, we show that these events produce infalling gas with solar abundances, which stron gly favours the Falling Evaporating Bodies (FEB) scenario.