Spectro-interferometry of the Be Star Sco: Near-infrared Continuum and Gas Emission Region Sizes in 2007

We present near-infrared H- and K-band spectro-interferometric observations of the gaseous disk around the primary Be star in the Sco binary system, obtained in 2007 (between periastron passages in 2000 and 2011). Observations using the CHARA/MIRC instrument at H band resolve an elongated disk with a Gaussian FWHM 1.18 × 0.91mas. Using the Keck Interferometer (KI), the source of the K-band continuum emission is only marginally spatially resolved, and consequently we estimate a relatively uncertain K-band continuum disk FWHM of 0.7 ± 0.3 mas. Line emission on the other hand, He I¿2.0583 ¿m and Br¿ ¿2.1657 ¿m, is clearly detected, with ~10% lower visibilities than those of the continuum. When taking into account the continuum/line flux ratio this translates into much larger sizes for the line emission regions: 2.2 ± 0.4 mas and 1.9 ± 0.3 mas for He I and Br¿, respectively. Our KI data also reveal a relatively flat spectral differential phase response,ruling out significant off-center emission. We expect that these new measurements will help constrain dynamical models being actively developed in order to explain the disk formation process in the Sco system and Be stars in general.