AAS 206th Meeting, 29 May - 2 June 2005
Session 14 Astrophysics with Optical Interferometry
Poster, Monday, 9:20am-6:30pm, Tuesday, 10:00am-7:00pm, May 30, 2005, Ballroom A

## [14.20] CHARA Commissioning Science Observations: The Diameter of \lambda Boötes

D. R. Ciardi, G. T. van Belle (MSC/Caltech), T. ten Brummelaar, H. A. McAlister, D. H. Berger (CHARA/GSU), R. R. Thompson (MSC/Caltech), C. Ogden, J. Sturmann, L. Sturmann, N. Turner, P. J. Goldfinger (CHARA/GSU), S. T. Ridgway (NOAO)

We present commissioning science observations with the CHARA array of \lambda Boötes. We have used the longest baselines of the CHARA array to observe the prototype of this subclass of unevolved A stars. \lambda Boötes is a chemically peculiar A star, with near-solar abundances of light elements such as C, N, O, & S ([Fe/H] \approx 0.0) and highly depleted abundances of heavy elements such as Mg, Ca, Fe, Ti, & Sr ([Fe/H] \approx -2.0). Our observations of \lambda Boo demonstrate that the star has an effective temperature of 10,280 ± 960 K typical of early A-type stars, but a linear radius of only 1.49 ± 0.28 R{\odot}. The star is 25% smaller than would be expected for an A0 star of solar metallicity, but the star is also 33% larger than would be expected for an A0 star of extremely low metallicity ([Fe/H] = -2.0). We discuss the implications of these unique observations performed with the CHARA array.

Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.