Olivier Absil, Emmanuel di Folco, Antoine Mérand, Vincent Coudé du Foresto, Jean-Charles Augereau, Jason P. Aufdenberg, Pierre Kervella, Stephen T. Ridgway, David H. Berger, Theo A. ten Brummelaar, Harold A. McAlister, Judit Sturmann, Lazslo Sturmann, and Nils H. Turner
HOT CIRCUMSTELLAR MATERIAL IN VEGA'S INNER PLANETARY SYSTEM

HOT CIRCUMSTELLAR MATERIAL IN VEGA'S INNER PLANETARY SYSTEM

Olivier Absil(1), Emmanuel di Folco(2), Antoine Mérand(3), Vincent Coudé du Foresto(3), Jean-Charles Augereau(4), Jason P. Aufdenberg(5), Pierre Kervella(3), Stephen T. Ridgway(5), David H. Berger(6), Theo A. ten Brummelaar(7), Harold A. McAlister(8), Judit Sturmann(7), Lazslo Sturmann(7), and Nils H. Turner(7)
(1)IAGL, Université de Liège
(2)Observatoire de Genève
(3)LESIA, Observatoire de Paris-Meudon
(4)Laboratoire d'Astrophysique de l'Observatoire de Grenoble
(5)National Optical Astronomy Observatory
(6)Univeristy of Michigan
(7)CHARA Array, Mt. Wilson Observatory
(8)CHARA, Georgia State University

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 ($<8$ 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 ( $\Delta V^2 \simeq 2$%), suggesting the presence of an extended source of emission around Vega. The sparse $(u, v)$ 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 $1.29 \pm 0.19$% 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.