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In 2005 we obtained very precise interferometric measurements of the pole-on rapid rotator Vega (A0 V) with the longest baselines of the Center for High Angular Angular Resolution (CHARA) Array and the Fiber Linked Unit for Optical Recombination (FLUOR). For the analysis of these data, we developed a code for mapping sophisticated PHOENIX model atmospheres on to the surface of rotationally distorted stars described by a Roche-von Zeipel formalism. Given a set of input parameters for a star or binary pair, this code predicts the interferometric visibility, spectral energy distribution and high-resolution line spectrum expected for the system. For the gravity-darkened Vega, our model provides a very good match to the K-band interferometric data, a good match to the spectral energy distribution - except below 160 nm - and a rather poor match to weak lines in the high dispersion spectrum where the model appears overly gravity darkened. In 2006, we used the CHARA Array and FLUOR to obtain high precision measurements of the massive, non-eclipsing, double-line spectroscopic binary Spica, a 4-day period system where both components are gravity darkened rapid rotators. These data supplement recent data obtained with the Sydney University Stellar Interferometer (SUSI). Our study follows the classic 1971 study by Herbison-Evans et al. who resolved Spica as a binary with the Narrabri Stellar Intensity Interferometer (NSII). We will report on our progress modeling the new interferometric and archival spectroscopic data, with the goal towards better constraining the apsidal constant

The bright star 55 Cancri is known to host five planets, including a transiting super-Earth. We use the CHARA Array to directly determine the following of 55 Cnc's stellar astrophysical parameters: $R=0.943 \pm 0.010 R_{\odot}$, $T_{\rm EFF} = 5196 \pm 24$ K. Planet 55 Cnc f ($M \sin i = 0.155 M_{Jupiter}$) spends the majority of the duration of its elliptical orbit in the circumstellar habitable zone (0.67--1.32 AU) where, with moderate greenhouse heating, it could harbor liquid water. Our determination of 55 Cancri's stellar radius allows for a model-independent calculation of the physical diameter of the transiting super-Earth 55 Cnc e ($\simeq 2.1 R_{\earth}$), which, depending on the assumed literature value of planetary mass, implies a bulk density of 0.76 $\rho_{\earth}$ or 1.07 $\rho_{\earth}$., Comment: 2 pages, 1 figure, 1 table. To appear in "Transiting Planets, Vibrating Stars, and Their Connection", Conference Proceedings of the 2nd CoRoT Symposium, Eds: A. Baglin, M. Deleuil, E. Michel, C. Moutou

We determined the spatial orientation of the Algol AB close pair orbital plane using optical interferometry with the CHARA Array, and radio interferometry with the European VLBI Network (EVN). We found the longitude of the line of nodes for the close pair being $\Omega_1=48\deg\pm2\deg$ and the mutual inclination of the orbital planes of the close and the wide pairs being $95\deg\pm3\deg$. This latter value differs by $5\deg$ from the formerly known $100\deg$ which would imply a very fast inclination variation of the system, not supported by the photometric observations. We also investigated the dynamics of the system with numerical integration of the equations of motions using our result as an initial condition. We found large variations in the inclination of the close pair (its amplitude $\sim 170\deg$) with a period of about 20 millenia. This result is in good agreement with the photometrically observed change of amplitude in Algol's primary minimum., Comment: in the conference proceedings of 'Binaries: key to comprehension of the Universe' (Brno, Czech Republic, 2009 June 8-12)

International audience; GJ 876 is a nearby M dwarf hosting four currently known extrasolar planets. We use the CHARA interferometric array to determine the stellar angular diameter. Coupled with trigonometric parallax values and literature photometry, we obtain direct estimates of the stellar physical size, surface temperature, luminosity, and location / extent of the system's habitable zone (HZ). We present our measurement results of the GJ 876 stellar astrophysical parameters and the location of the HZ relative to the planetary orbits.