Protostars and Planets VI, Heidelberg, July 15-20, 2013
ET Cha - a single T Tauri star with a disk of radius 5 AU ?
Woitke, P. (UPA, School of Physics & Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS, UK)
Dent, W.R.F. (ALMA, Avda Apoquindo 3846, Piso 19, Edificio Alsacia, Las Condes, Santiago, Chile)
Thi, W.-F. (UJF-Grenoble 1 / CNRS-INSU, Institut de Planétologie et d’Astrophysique (IPAG) UMR 5274, 38041 Grenoble, France)
Menard, F. (UJF-Grenoble 1 / CNRS-INSU, Institut de Planétologie et d’Astrophysique (IPAG) UMR 5274, 38041 Grenoble, France)
Pinte, C. (UJF-Grenoble 1 / CNRS-INSU, Institut de Planétologie et d’Astrophysique (IPAG) UMR 5274, 38041 Grenoble, France)
Duchene, G. (Astronomy Department, University of California, Berkeley, CA 94720-3411, USA)
Sandell, G. (SOFIA-USRA, NASA Ames Research Center, USA)
Lawson, W. (School of Physical, Environmental and Mathematical Scienc es, University of New South Wales, Canberra, ACT 2600, Austr alia)
Kamp, I. (Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands)
The 6-8 Myrs old M3-type TTauri star ET Cha (aka RECX 15) is a member of the eta Chamaeleontis moving group at a distance of about 94pc. Its protoplanetary disc was easily detected by Spitzer (IRAC, MIPS, IRS) in the near and mid-IR, and optical and near-IR line observations show clear evidence for active accretion (∼1.E-9 Msun/yr), outflows (also ∼1.E-9 Msun/yr), and H2 in the disc. However, previous attempts to detect this source in the sub-mm failed, including the search for CO J=3-2 with APEX, because ET Cha is apparently extraordinary faint at longer wavelengths. In a previous paper, Woitke et al.(2011) concluded that this disc must be exceptionally small (<10 AU) in order to explain all the available continuum and line data.
We present new cycle-0 ALMA data that show a clear detection of ET Cha at 850um continuum, as well as a 7-sigma detection of the CO J=3-2 line. The CO emission is characterised by a double-peak emission profile with FHWM ∼15 km/s, which suggests an outer disc radius of only about 5 AU. We discuss these results by means of the Monte-Carlo radiative transfer program MCMax (main developer Michiel Min) and the radiation thermo-chemical gas code ProDiMo (main developers Peter Woitke, Wing-Fai Thi and Inga Kamp), which have been coupled in the frame of the European FP7-2011-SPACE project DIANA, under grant agreement no 284405.
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