What Are the True Sizes of Retired A Stars?



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To find exoplanets, it is important to have accurate measurements for potential host stars to make it easier to tell when something changes that might indicate the presence of an exoplanet. A-type stars, which have up to about twice the mass of our Sun, rotate very fast, making it hard to see if an exoplanet's gravity is tugging on them. However, when these stars have aged and cooled into subgiants, they rotate slower, making it easier to spot planets around them. This project uses near-infrared data from Georgia State University’s Center for High Angular Resolution Astronomy (CHARA) on Mount Wilson, CA, to accurately measure the radii of five retired A stars. Models make it possible to predict the stars’ luminosity, temperature, age, and mass from the radii measurements. The measurements of these five properties are then compared to the properties estimated by existing literature, which generally uses broad-band photometric data and derives the radius using a chart rather than measuring it directly. Hypothetically, there will be a systematic offset in the measured values as compared to the literature values. This comparison will help to refine the models and lead to more accurate measurements of retired A star radii — and lead to more exoplanet discoveries.



Retired A stars, Star angular diameter, Interferometry, Exoplanet detection, Radial velocity method