A&A 489, 1151-1155 (2008)
DOI: 10.1051/0004-6361:200809627

Spatially resolving the hot CO around the young Be star 51 Ophiuchi

E. Tatulli^{1, 2}, F. Malbet², F. Ménard², C. Gil³, L. Testi^{1, 4}, A. Natta¹, S. Kraus⁵, P. Stee⁶, and S. Robbe-Dubois<sup>7

1</sup>  INAF-Osservatorio Astrofisico di Arcetri, Istituto Nazionale di Astrofisica, Largo E. Fermi 5, 50125 Firenze, Italy
²  Laboratoire d'Astrophysique de Grenoble, UMR 5571 Université Joseph Fourier/CNRS, BP 53, 38041 Grenoble Cedex 9, France
    e-mail: Eric.Tatulli@obs.ujf-grenoble.fr
³  European Southern Observatory, Casilla 19001, Santiago 19, Chile
⁴  ESO, Karl-Schwarzschild Strasse 2, 85748 Garching bei Muenchen, Germany
⁵  Max Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁶  UMR 6525 CNRS H. FIZEAU UNS, OCA, Campus Valrose, 06108 Nice Cedex 2, France; CNRS, Avenue Copernic, Grasse, France
⁷  Laboratoire Universitaire d'Astrophysique de Nice, UMR 6525 Université de Nice/CNRS, Parc Valrose, 06108 Nice Cedex 2, France

Received 21 February 2008 / Accepted 30 June 2008

Abstract
Aims. 51 Oph is one of the few young Be stars displaying a strong CO overtone emission at 2.3 microns in addition to the near infrared excess commonly observed in this type of stars. In this paper we first aim to locate the CO bandheads emitting region. Then, we compare its position with respect to the region emitting the near infrared continuum.
Methods. We have observed 51 Oph with AMBER in low spectral resolution (R = 35), and in medium spectral resolution (R = 1500) centered on the CO bandheads.
Results. The medium resolution AMBER observations clearly resolve the CO bandheads. Both the CO bandheads and continuum emissions are spatially resolved by the interferometer. Using simple analytical ring models to interpret the measured visibilities, we find that the CO bandheads emission region is compact, located at  AU from the star, and that the adjacent continuum is coming from a region further away (  AU). These results confirm the commonly invoked scenario in which the CO bandheads originate in a dust free hot gaseous disk. Furthermore, the continuum emitting region is closer to the star than the dust sublimation radius (by at least a factor two) and we suggest that hot gas inside the dust sublimation radius significantly contributes to the observed 2 m continuum emission.

Key words: Techniques: interferometric -- stars: individual: 51 Oph -- planetary systems: protoplanetary disks

© ESO 2008

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