SPECTRO-INTERFEROMETRY OF THE Be STAR {delta} Sco: NEAR-INFRARED CONTINUUM AND GAS EMISSION REGION SIZES IN 2007

• Published in: The Astrophysical journal 2010-11, Vol.723 (1)
• Main Authors: Millan-Gabet, R., Monnier, J. D., Touhami, Y., Gies, D., Hesselbach, E., Pedretti, E., Thureau, N., Zhao, M., Ten Brummelaar, T.
• Format: Article
• Language: English
• Subjects: ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; EMISSION; INTERFEROMETERS; INTERFEROMETRY; MEASURING INSTRUMENTS; RESOLUTION; STARS
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/723/1/544

We present near-infrared H- and K-band spectro-interferometric observations of the gaseous disk around the primary Be star in the {delta} 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 x 0.91 mas. 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 {lambda}2.0583 {mu}m and Br{gamma} {lambda}2.1657 {mu}m, is clearly detected, with {approx}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{gamma}, 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 {delta} Sco system and Be stars in general.