Outer atmospheres of M-supergiant stars

A reanalysis of the physical structure of the outer atmospheres of the M-supergiants was undertaken. The observational data includes old Hale Observatories plates, recent 82'' plates, recent 107'' photoelectric scans and ultraviolet Copernicus satellite scans. These data are analysed in the full expanding extended geometry formulation of the radiative transfer equation. The numerical method of solution follows Kunasz and Hummer with extensions to a true shall surrounding a bright, opaque core and a multi-level atom. A major result of the combined analysis is a theoretical prediction of the possibility of observationally detectable emission due to scattering in the gas shells and subsequent observational verification. Detailed mapping of the KI resonance line re-emission around Betelgeuse shows evidence for asymmetries in the distribution of gas. Analysis with the results of the extended geometry calculations indicates that column densities in the gas shells must be revised downward, but that the physical extents of the shells are considerably larger than previously assumed. The physical extent of the gas shells is inferred through ionization modelling and directly observed through the re-emission process. Mass loss rates in the range 1 x 10-6 to 2 x 10-4 solar masses per year are inferred. The influence of these large rates of mass loss on both the evolution of the star and of the galaxy is discussed. Null results from the attempted detection of several chromospheric-coronal lines in Betelgeuse allow ruling out the possibility of hot, extended circumphotospheric regions in these stars. Analysis of the MgPI h and k lines observed with the Copernicus satellite indicates the presence of an optically thick, turbulent region between the chromospheres and cool gas shells of these stars