Stellar wind properties of A-type hypergiants.

Abstract

The visually bright objects from the Magellanic Clouds are examined in terms of observed properties that indicate properties relevant to the stellar wind. IUE observations are accomplished in the long-wavelength primary echelle mode in the optical wavelength near H-alpha of the objects HD 33579 and HD 7583. The Fe-II lines are found to have widths that are dependent upon log gf and the excitation potential; these dependencies relate to an accelerated wind that is directed outwards. The terminal velocity is found to be approximately equal to 200 km/s for both stars as evinced by the strong Fe-II lines. A flat velocity law is determined and a mass-loss rate of 2 x 10 exp 6 solar mass/yr is given for both of the stars. The wind properties of the A-types are concluded to relate to a uniform acceleration mechanism.