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Vega: A rapidly rotating pole-on star
Gulliver, Austin F.; Hill, Graham; Adelman, Saul J.
AA(Brandon Univ., Brandon, Canada), AB(Brandon Univ., Brandon, Canada), AC(The Citadel, Charleston, SC, US)
The Astrophysical Journal, vol. 429, no. 2, pt. 2, p. L81-L84 (ApJL Homepage)
Publication Date:
NASA/STI Keywords:
Atoms, Ions, Iron, Line Spectra, Lyra Constellation, Rotating Bodies, Spectral Line Width, Titanium, High Dispersion Spectrographs, Signal To Noise Ratios, Telescopes
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High-dispersion (2.4 A/mm), ultrahigh signal-to-noise ratio (3000:1) Reticon spectra of Vega revealed two distinct types of profiles. The strong lines exhibit classical rotational profiles with enhanced wings, but the weak lines have distinctly different, flat-bottomed profiles. Using ATLAS9 model atmopheres and SYNTHE synthetic spectra, Vega has been modeled as a rapidly rotating, pole-on star with a gradient in temperature and gravity over the photosphere. By fitting to the flat-bottomed line profiles of Fe 1 lambda 4528 and Ti 2 lambda 4529, we find least-squares fit values of V sin i = 21.8 plus or minus 0.2 km/sec polar Teff = 9695 plus or minus 25 K, polar log(base 10)g = 3.75 plus or minus 0.02 dex, Veq = 245 plus or minus 15 km/sec, and inclination 5 deg .1 plus or minus 0 deg .3. The variations in Teff and log(base 10)g over the photosphere total 390 K and 0.08 dex, respectively. Assuming V sin i = 21.8 km/sec, an independent fit to the observed continuous flux from 1200 to 10,500 A produced a similar set of values with polar Teff = 9595 plus or minus 20 K, polar log(base 10)g = 3.80 plus or minus 0.03 dex, and inclination 6 deg .0 plus or minus 0 deg .7.

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