Imaging And Modeling Rapidly Rotating Stars: Rasalhague And Alderamin
Abstract
Stellar rotation is a fundamental property of stars. Although the effects of rotation on solar type stars are relatively mild, they are more prominent on hot stars and can strongly affect the stars' luminosity, Teff, and life time, etc. Here we present high resolution (<1mas) aperture sythesis images on two of nearby rapid rotators: Rasalhague and Alderamin, obtained using CHARA-MIRC. The images show that both of these two stars are obviously oblate due to their rapid rotation. Furthermore the brightness of their equators are darker than their poles - a direct confirmation of gravity-darkening. Specifically our models indicate that Rasalhague is rotating at 92% of break-up velocity and is seen nearly edge-on. Its temperature at the poles is 2250K higher than its equator, indicating that its apparent Teff is strongly biased by its orientation. Alderamin is rotating even faster, at 96% of break-up and has a more prominent temperature difference between equator and the poles. It is inclined by 60 degs and its orientation is different from previous study. In addition to the standard uniformly rotating, gravity-darkening models, we also explore non-standard models on both stars.
- Publication:
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American Astronomical Society Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AAS...21110325Z