A STUDY OF VEGA: A RAPIDLY ROTATING POLE-ON STAR

Ultra-high signal-to-noise, high dispersion spectroscopy over the wavelength range lambda lambda 4519-4535 shows Vega to be a rapidly rotating star with V(eq) of 211 km s(-1) seen almost pole-on. The analysis of five independent series of spectroscopic data is combined with analyses of the hydrogen lines, H gamma, H beta, and H alpha, and the latest absolute continuum flux for Vega to yield the following results: V sin i = 20.8 +/- 0.2 km s(-1), polar T(eff) = 10,000 +/- 30 K, polar log g = 4.04 +/- 0.01 dex, V(eq) = 211 +/- 4 km s(-1), breakup fraction = 0.81 +/- 0.02, microturbulence (xi(T)) = 1.0 +/- 0.1 km s(-1), macroturbulence (zeta) = 7.4 +/- 0.5 km s(-1), and an inclination i = 5 degrees.7 +/- 0 degrees.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 angstrom profile are also illustrated.