Magnetospheric accretion on the fully-convective classical T Tauri star DN Tau
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We report here results of spectropolarimetric observations of the classical T Tauri star DN Tau carried out (at 2 epochs) with ESPaDOnS at the Canada–France–Hawaii Telescope within the ‘Magnetic Protostars and Planets’ programme. We infer that DN Tau, with a photospheric temperature of 3950 ± 50 K, a luminosity of 0.8 ± 0.2 L⊙ and a rotation period of 6.32 d, is a ≃2 Myr-old fully convective 0.65 ± 0.05 M⊙ star with a radius of 1.9 ± 0.2 R⊙, viewed at an inclination of 35 ± 10°. Clear circularly polarized Zeeman signatures are detected in both photospheric and accretion-powered emission lines, probing longitudinal fields of up to 1.8 kG (in the He i D3 accretion proxy). Rotational modulation of Zeeman signatures, detected both in photospheric and accretion lines, is different between our two runs, providing further evidence that fields of classical T Tauri stars are generated by non-stationary dynamos. Using tomographic imaging, we reconstruct maps of the large-scale field, of the photospheric brightness and of the accretion-powered emission at the surface of DN Tau at both epochs. We find that the magnetic topology is mostly poloidal, and largely axisymmetric, with an octupolar component (of polar strength 0.6–0.8 kG) 1.5–2.0 times larger than the dipolar component (of polar strength ≃0.3–0.5 kG). DN Tau features dominantly poleward accretion at both epochs. The large-scale dipole component of DN Tau is however too weak to disrupt the surrounding accretion disc further than 65–90 per cent of the corotation radius (at which the disc Keplerian period matches the stellar rotation period), suggesting that DN Tau is already spinning up despite being fully convective.
Donati , J F , Gregory , S , Alencar , S H P , Hussain , G , Bouvier , J , Jardine , M M , Menard , F , Dougados , C & Romanova , M M 2013 , ' Magnetospheric accretion on the fully-convective classical T Tauri star DN Tau ' Monthly Notices of the Royal Astronomical Society , vol 436 , no. 1 , pp. 881-897 . DOI: 10.1093/mnras/stt1622
Monthly Notices of the Royal Astronomical Society
© 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society
DescriptionThe MaPP project is supported by the funding agencies of CFHT and TBL (through the allocation of telescope time) and by INSU/CNRS in particular, as well as by the French ‘Agence Nationale pour la Recherche’ (ANR). SGG acknowledges support from the Science and Technology Facilities Council (STFC) via an Ernest Rutherford Fellowship [ST/J003255/1]. SHPA acknowledges support from CNPq, CAPES and Fapemig. FM acknowledges support from the Millennium Science Initiative (Chilean Ministry of Economy), through grant ‘Nucleus P10-022-F’.
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