Vega: A Rapidly Rotating Poleon Star
Abstract
Highdispersion (2.4 A/mm), ultrahigh signaltonoise 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, flatbottomed profiles. Using ATLAS9 model atmopheres and SYNTHE synthetic spectra, Vega has been modeled as a rapidly rotating, poleon star with a gradient in temperature and gravity over the photosphere. By fitting to the flatbottomed line profiles of Fe 1 lambda 4528 and Ti 2 lambda 4529, we find leastsquares fit values of V sin i = 21.8 plus or minus 0.2 km/sec polar T_{eff} = 9695 plus or minus 25 K, polar log(base 10)g = 3.75 plus or minus 0.02 dex, V_{eq} = 245 plus or minus 15 km/sec, and inclination 5 deg .1 plus or minus 0 deg .3. The variations in T_{eff} 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 T_{eff} = 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.
 Publication:

The Astrophysical Journal
 Pub Date:
 July 1994
 DOI:
 10.1086/187418
 Bibcode:
 1994ApJ...429L..81G
 Keywords:

 Atoms;
 Ions;
 Iron;
 Line Spectra;
 Lyra Constellation;
 Rotating Bodies;
 Spectral Line Width;
 Titanium;
 High Dispersion Spectrographs;
 Signal To Noise Ratios;
 Telescopes;
 Astronomy;
 STARS: ATMOSPHERES;
 STARS: EARLYTYPE;
 STARS: INDIVIDUAL CONSTELLATION NAME: ALPHA LYRAE