The presence of Si3+ and C3+ in the wind of AB Aur.

Abstract

The Herbig Ae variable AB Aur (spectral type A0) exhibits a line spectrum characteristic of a stellar wind. IUE observations of the Si IV and C IV resonance lines in AB Aur are reported. These lines are strong and in absorption. Two models can explain the presence of Si³⁺ and C³⁺ in the wind of AB Aur: a "remote chromosphere" model, with a temperature rise up to 10⁵K, occurring beyond the point where the ionizing radiation begins to depart from the local Planck function, and a "deep chromosphere" model, with a temperature rise up to 15,000 - 18,000K, located just above the stellar photosphere. Several additional observational arguments are in favor of the "deep chromosphere" model.