Surface magnetic fields on two accreting T Tauri stars: CV Cha and CR Cha |
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Authors: | G A J Hussain A Collier Cameron M M Jardine N Dunstone J Ramirez Velez H C Stempels J-F Donati M Semel G Aulanier T Harries J Bouvier C Dougados J Ferreira B D Carter W A Lawson |
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Institution: | ESO, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany;SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, Fife KY16 9SS;LESIA, Observatoire de Paris, Section de Meudon, 92195 Meudon Principal Cedex, France;LATT, CNRS-UMR 5572, Obs. Midi-Pyrénées, 14 Av. E. Belin, F-31400 Toulouse, France;School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL;LAOG, Laboratoire d'Astrophysique, Obs. de Grenoble, UMR-5571, CNRS, Univ. J Fourier, F-38041 Grenoble, France;Faculty of Sciences, University of Southern Queensland, Toowoomba 4350, Australia;School of Physical, Environmental and Mathematical Sciences, University of New South Wales, Australian Defence Force Academy, Canberra, ACT 2600, Australia |
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Abstract: | We have produced brightness and magnetic field maps of the surfaces of CV Cha and CR Cha: two actively accreting G- and K-type T Tauri stars in the Chamaeleon I star-forming cloud with ages of 3–5 Myr. Our magnetic field maps show evidence for strong, complex multipolar fields similar to those obtained for young rapidly rotating main-sequence stars. Brightness maps indicate the presence of dark polar caps and low-latitude spots – these brightness maps are very similar to those obtained for other pre-main-sequence and rapidly rotating main-sequence stars. Only two other classical T Tauri stars have been studied using similar techniques so far: V2129 Oph and BP Tau. CV Cha and CR Cha show magnetic field patterns that are significantly more complex than those recovered for BP Tau, a fully convective T Tauri star. We discuss possible reasons for this difference and suggest that the complexity of the stellar magnetic field is related to the convection zone; with more complex fields being found in T Tauri stars with radiative cores (V2129 Oph, CV Cha and CR Cha). However, it is clearly necessary to conduct magnetic field studies of T Tauri star systems, exploring a wide range of stellar parameters in order to establish how they affect magnetic field generation, and thus how these magnetic fields are likely to affect the evolution of T Tauri star systems as they approach the main sequence. |
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Keywords: | stars: formation stars: imaging stars: individual: CR Cha stars: individual: CV Cha stars: magnetic fields open clusters and associations: individual: Chamaeleon I |
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