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Stellar Diameters

The CHARA Array measures the sizes of stars across a large range of masses and evolutionary stages (e.g., Boyajian et al. 2012a, 2012b, 2013).  The angular diameter of a star, when combined with the stellar parallax (measured through astrometric missions like Hipparcos or GAIA), provides a direct measurement of the physical radius of the star.  If the bolometric flux of the star is measured from its spectral energy distribution, then an empirical measurement of the stellar effective temperature can be derived through Stefan's Law (Fbol = ¼ θ2σT4).

Empirical Hertzsrpung-Russell Diagram showing ~290 stars with sizes measured with long-baseline optical/infrared interferometry (from von Braun & Boyajian 2017, in Extrasolar Planets and Their Host Stars, Springer).  All of the stars have stellar radii with random uncertainties smaller than 5%, stellar radii < 100 Rsun, and distances up to 150 pc.The size of the plotting symbols corresponds to the logarithm of the stellar radius.

 

The fundamental parameters of a star (radius, effective temperature, luminosity) can be compared with evolutionary models to estimate the mass and age of a star (Jones et al. 2015, Ligi et al. 2016).

 

References:

Boyajian et al. 2012, ApJ, 746, 101

Boyajian et al. 2012, ApJ, 757, 112 

Boyajian et al. 2013, ApJ, 771, 40

von Braun & Boyajian 2017, in Extrasolar Planets and Their Host Stars, Springer