Journal Article

Complex magnetic topology and strong differential rotation on the low-mass T Tauri star V2247 Oph*

J.-F. Donati, M. B. Skelly, J. Bouvier, M. M. Jardine, S. G. Gregory, J. Morin, G. A. J. Hussain, C. Dougados, F. Ménard and Y. Unruh

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 402, issue 3, pages 1426-1436
Published in print March 2010 | ISSN: 0035-8711
Published online February 2010 | e-ISSN: 1365-2966 | DOI: https://dx.doi.org/10.1111/j.1365-2966.2009.15998.x
Complex magnetic topology and strong differential rotation on the low-mass T Tauri star V2247 Oph*

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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.

Keywords: techniques: polarimetric; stars: formation; stars: imaging; stars: individual: V2247 Oph; stars: magnetic fields; stars: rotation

Journal Article.  7834 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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