A near-infrared interferometric survey of debris disk stars. I. Probing the hot dust content around ε Eridani and τ Ceti with CHARA/FLUOR

• Published in: Astronomy and astrophysics (Berlin) Vol. 475; no. 1; pp. 243 - 250
• Main Authors: DI FOLCO, E, ABSIL, O, RIDGWAY, S. T, STURMANN, J, STURMANN, L, TURNER, N. H, AUGEREAU, J.-C, MERAND, A, COUDE DU FORESTO, V, THEVENIN, F, DEFRERE, D, KERVELLA, P, TEN BRUMMELAAR, T. A, MCALISTER, H. A
• Format: Journal Article
• Language: English
• Published: Les Ulis EDP Sciences 01.11.2007
• Subjects: Astronomy; Chara; Earth, ocean, space; Exact sciences and technology; USA; Infrared surveys; stars: individual: τ Cet & ∈ Eri; methods: observational; Dust grain; Dynamics; Infrared interferometry; Stellar photospheres; Circumstellar matter; stars: fundamental parameters; Visibility; techniques: interferometric; Angular diameter
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361:20077625

Context. The quest for hot dust in the central region of debris disks requires high resolution and high dynamic range imaging. Near-infrared interferometry is a powerful means to directly detect faint emission from hot grains. Aims. We probed the first 3 AU around \tau Ceti and \epsilon Eridani with the CHARA array (Mt Wilson, USA) in order to gauge the 2 \mum excess flux emanating from possible hot dust grains in the debris disks and to also resolve the stellar photospheres. Methods. High precision visibility amplitude measurements were performed with the FLUOR single mode fiber instrument and telescope pairs on baselines ranging from 22 to 241 m of projected length. The short baseline observations allow us to disentangle the contribution of an extended structure from the photospheric emission, while the long baselines constrain the stellar diameter. Results. We have detected a resolved emission around \tau Cet, corresponding to a spatially integrated, fractional excess flux of 0.98\pm0.21 \times 10 with respect to the photospheric flux in the K{\prime}-band. Around \epsilon Eri, our measurements can exclude a fractional excess of greater than 0.6\times 10 (3\sigma). We interpret the photometric excess around \tau Cet as a possible signature of hot grains in the inner debris disk and demonstrate that a faint, physical or background, companion can be safely excluded. In addition, we measured both stellar angular diameters with an unprecedented accuracy: \Theta_{\rm LD}(\tau\,{\rm Cet}) = 2.015 \pm 0.011 mas and \Theta_{\rm LD}(\epsilon\,{\rm Eri}) =2.126 \pm 0.014 mas.