The Angular Diameter of λ Boötis

Using the CHARA Array and the Palomar Testbed Interferometer, the chemically peculiar star λ Boötis has been spatially resolved. We have measured the limb darkened angular diameter to be θLD = 0.533 ± 0.029 mas, corresponding to a linear radius of R⋆ = 1.70 ± 0.10 R☉. The measured angular diameter yields an effective temperature for λ Boo of Teff = 8887 ± 242 K. Based on literature surface gravity estimates spanning log g = 4.0-4.2 cm s-2, we have derived a stellar mass range of M⋆ = 1.1-1.7 M☉. For a given surface gravity, the linear radius uncertainty contributes approximately σ(M⋆) = 0.1-0.2 M☉ to the total mass uncertainty. The uncertainty in the mass (i.e., the range of derived masses) is primarily a result of the uncertainty in the surface gravity. The upper bound of our derived mass range (log g = 4.2, M⋆ = 1.7 ± 0.2 M☉) is consistent with 100-300 Myr solar metallicity evolutionary models. The midrange of our derived masses (log g = 4.1, M⋆ = 1.3 ± 0.2 M☉) is consistent with 2-3 Gyr metal-poor evolutionary models. A more definitive surface gravity determination is required to determine a more precise mass for λ Boo.