2010ApJ...712..250H

Ultra-high signal-to-noise, high dispersion spectroscopy over the wavelength range λλ4519-4535 shows Vega to be a rapidly rotating star with V_eq of 211 km/s seen almost pole-on. The analysis of five independent series of spectroscopic data is combined with analyses of the hydrogen lines, Hγ, Hβ, and Hα, and the latest absolute continuum flux for Vega to yield the following results: Vsin i = 20.8±0.2 km/s, polar T_eff= 10, 000±30 K, polar log g = 4.04±0.01 dex, V_eq= 211±4 km/s, breakup fraction = 0.81±0.02, microturbulence (ξ_T) = 1.0 ±0.1 km/s, macroturbulence (ζ) = 7.4±0.5 km/s, and an inclination i = 5{fdg}7±0{fdg}1. The variations in T_eff and log g over the photosphere total 1410 K and 0.26 dex, respectively, while the mean temperature is 9560 ±30 K and log g is 3.95±0.01 dex. Low level variations in the Ti II 4529 Å profile are also illustrated.