delta Cen: a new binary Be star detected by VLTI/AMBER spectro-interferometry
Résumé
Aims. We studied the Be star δ Cen circumstellar disk using long-baseline interferometry which is the only observing technique able to resolve simultaneously, spatially and spectroscopically objects smaller than 5 mas in the H and K band. Methods. We used the VLTI/AMBER instrument on January 6, 8, and 9, 2008, in the H and K bands combining Low (35) and Medium (1500) spectral resolution observations. Results. We detected an oscillation in the visibility curve as a function of the spatial frequency which is a clear signature for a companion around δ Cen. Our best fit leads us to a binary separation of 68.7 mas, a companion flux contribution in the K band of about 7% of the total flux, a PA of 117.5 ◦ and an envelope flux around the Be primary contributing to about 50 % of the total flux, in agreement with our Spectral Energy Distribution (SED) fit. The envelope size is estimated to be 1.6 mas in K but no departure from the spherical symmetry was detected.
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