Complex magnetic topology and strong differential rotation on the low-mass T Tauri star V2247 Oph
Abstract
From observations collected with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope, we report the detection of Zeeman signatures on the low-mass classical T Tauri star (cTTS) V2247 Oph. Profile distortions and circular polarization signatures detected in photospheric lines can be interpreted as caused by cool spots and magnetic regions at the surface of the star. The large-scale field is of moderate strength and highly complex; moreover, both the spot distribution and the magnetic field show significant variability on a time-scale of only 1 week, as a likely result of strong differential rotation. Both properties make V2247 Oph very different from the (more massive) prototypical cTTS BP Tau; we speculate that this difference reflects the lower mass of V2247 Oph.
During our observations, V2247 Oph was in a low-accretion state, with emission lines showing only weak levels of circular polarization; we nevertheless find that excess emission apparently concentrates in a mid-latitude region of a strong radial field, suggesting that it is the footpoint of an accretion funnel. The weaker and more complex field that we report on V2247 Oph may share similarities with those of very-low-mass late-M dwarfs and potentially explain why low-mass cTTSs rotate on average faster than intermediate-mass ones. These surprising results need confirmation from new independent data sets on V2247 Oph and other similar low-mass cTTSs. Based on observations obtained at the Canada-France-Hawaii Telescope, operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France and the University of Hawaii. E-mail: donati@ast.obs-mip.fr (J-FD); mskelly@ast.obs-mip.fr (MBS); jerome.bouvier@obs.ujf-grenoble.fr (JB); mmj@st-andrews.ac.uk (MMJ); sg64@st-andrews.ac.uk (SGG); jmorin@ast.obs-mip.fr (JM); ghussain@eso.org (GAJH); catherine.dougados@obs.ujf-grenoble.fr (CD); francois.menard@obs.ujf-grenoble.fr (FM); y.unruh@imperial.ac.uk (YU)- Publication:
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Monthly Notices of the Royal Astronomical Society
- Pub Date:
- March 2010
- DOI:
- 10.1111/j.1365-2966.2009.15998.x
- arXiv:
- arXiv:0911.1080
- Bibcode:
- 2010MNRAS.402.1426D
- Keywords:
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- techniques: polarimetric;
- stars: formation;
- stars: imaging;
- stars: individual: V2247 Oph;
- stars: magnetic fields;
- stars: rotation;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- MNRAS (in press) - 12 pages, 9 figures