CAOSP abstracts, Volume: 38, No.: 2, year: 2008

Abstract: In order to establish Vega's absolute rotational velocity (v_e) separated from the inclination angle (i), while making use of the fact that information on rotation-induced gravity darkening is reflected in the characteristic spectral line shapes, we conducted a detailed profile study on a large number of weak lines based on the very high S/N spectrum data, and concluded that v_e ≃ 175 km s^-1 (with i ≃ 7^°) is the best solution. It also turned out that the conventionally derived abundances from Fe I lines by using classical model atmospheres tend to be overestimated by up to ∼ 0.2 dex, though this effect is insignificant for Fe II lines. Such gravity-darkening corrections may have an appreciable impact on the Fe I/Fe II ionization equilibrium as well as on the determination of the microturbulence.