The Chara Array Angular Diameter of HR 8799 Favors Planetary Masses for Its Imaged Companions
NAVAL RESEARCH LAB WASHINGTON DC REMOTE SENSING DIV
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HR8799 is an hF0 mA5 gamma Doradus-, lambda Bootis-,Vega-type star best known for hosting four directly imaged candidate planetary companions. Using the CHARA Array interferometer, we measure HR 8799s limb-darkened angular diameter to be 0.342 - 0.008 mas an error of only 2. By combining our measurement with the stars parallax and photometry from the literature, we greatly improve upon previous estimates of its fundamental parameters including stellar radius 1.44 - 0.06 R , effective temperature 7193 - 87 K, consistent with F0, luminosity 5.05 -0.29 L , and the extent of the habitable zone HZ 1.62-3.32 AU. These improved stellar properties permit much more precise comparisons with stellar evolutionary models, from which a mass and age can be determined once the metallicity of the star is known. Considering the observational properties of other lambda Bootis stars and the indirect evidence for youth of HR 8799, we argue that the internal abundance, and what we refer to as the effective abundance, is most likely near solar.