The binary Be star δ Sco at high spectral and spatial resolution: Disk geometry and kinematics before the 2011 periastron

Abstract

Classical Be stars are hot non-supergiant stars surrounded by a gaseous circumstellar disk that is responsible for the observed IR-excess and emission lines. The influence of binarity on these phenomena remains controversial. delta Sco is a binary system whose primary suddently began to exhibit the Be phenomenon at the last periastron in 2000. We want to constrain the geometry and kinematics of its circumstellar environment. We observed the star between 2007 and 2010 using spectrally-resolved interferometry with the VLTI/AMBER and CHARA/VEGA instruments. We found orbital elements that are compatible with previous estimates. The next periastron should take place around July 5, 2011 (+- 4,days). We resolved the circumstellar disk in the HAlpha (FWHM = 4.8+-1.5mas), BrGamma (FWHM = 2.9 0.,mas), and the 2.06$\mu$m HeI (FWHM = 2.4+-0.3mas) lines as well as in the K band continuum (FWHM ~2.4mas). The disk kinematics are dominated by the rotation, with a disk expansion velocity on the order of 0.2km/s. The rotation law within the disk is compatible with Keplerian rotation. As the star probably rotates at about 70% of its critical velocity the ejection of matter doesn't seems to be dominated by rotation. However, the disk geometry and kinematics are similar to that of the previously studied quasi-critically rotating Be stars, namely Alpha Ara, Psi Per and 48 Per.

A\&A accepted paper

References in corpus (6)

• Effects of gravitational darkening on the determination of fundamental parameters in fast rotating B-type stars
• Penumbral fine structure and driving mechanisms of large-scale flows in simulated sunspots
• An asymmetry detected in the disk of Kappa CMa with the AMBER/VLTI
• Eccentric binaries: Tidal flows and periastron events
• The close-in companion of the fast rotating Be star Achernar
• delta Cen: a new binary Be star detected by VLTI/AMBER spectro-interferometry

Cited by in corpus (12)

• A CHARA Array Survey of Circumstellar Disks around Nearby Be-type Stars
• The X-ray emission of the gamma Cassiopeiae stars
• Gas Distribution, Kinematics, and Excitation Structure in the Disks around the Classical Be Stars Beta Canis Minoris and Zeta Tauri
• Probing the properties of Be star discs with spectroastrometry and NLTE radiative transfer modelling: beta CMi
• X-ray study of bow shocks in runaway stars
• The 2011 Periastron Passage of the Be Binary delta Scorpii
• Interferometry concepts
• The peculiar fast-rotating star 51 Oph probed by VEGA/CHARA
• Differential interferometry of close binary of supermassive black holes in an elliptical configuration
• The binary Be star $\delta$ Scorpii at high spectral and spatial resolution : II The circumstellar disk evolution after the periastron
• Observation of double star by long-baseline interferometry
• Delta Scorpii 2011 periastron: worldwide observational campaign and preliminary photometric analysis