Using the FLUOR beam-combiner installed at the CHARA Array (Mt Wilson, CA), we have obtained high-precision visibility measurements of Vega,
one of the prototypic debris-disk stars, known to be surrounded by
large amounts of cold dust in a ring-like structure at 80-100 AU. The
combination of short and long baselines has allowed us to separately
resolve the stellar photosphere and the close environment of the star
( AU). Our observations show a significant deficit in square
visibility at short baselines with respect to the expected visibility
of a simple uniform disk stellar model (
%),
suggesting the presence of an extended source of emission around Vega.
The sparse
plane coverage does not allow for discriminating
between a point source and an extended circumstellar emission as the
origin of the extended emission. However, we show that the presence of
a point-like source within the FLUOR field-of-view (1 arcsec in radius
= 7.7 AU at the distance of Vega) is highly unlikely, and propose that
the excess emission is most likely due to the presence of hot
circumstellar dust in the inner part of Vega's debris disk, with a flux
ratio of
% between the integrated dust emission and the
stellar photosphere. Using this information together with archival
photometric measurements in the near- and mid-infrared, we derive the
expected physical properties of the circumstellar dust by modelling its
infrared Spectral Energy Distribution. The inferred properties suggest
that the Vega system could be currently undergoing major dynamical
perturbations.