EDP Sciences
Free access
Volume 406, Number 2, August I 2003
Page(s) 703 - 707
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20030833

A&A 406, 703-707 (2003)
DOI: 10.1051/0004-6361:20030833

Resolved polarization changes across H $\alpha$ in the classical T Tauri star RY Tauri

Jorick S. Vink1, J. E. Drew1, T. J. Harries2, R. D. Oudmaijer3 and Y. C. Unruh1

1  Imperial College of Science, Technology & Medicine, Blackett Laboratory, Prince Consort Road, London, SW7 2BZ, UK
2  School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK
3  The Department of Physics and Astronomy, E C Stoner Building, Leeds, LS2 9JT, UK

(Received 1 April 2003 / Accepted 3 June 2003)

We present linear H $\alpha$ spectropolarimetry of the classical T Tauri star RY Tau. A change in the polarization percentage and position angle across H $\alpha$ is detected, which suggests that line photons are scattered in a rotating disc. We derive the position angle from the slope of the loop in the (Q,U) diagram and find it to be 146 $\pm$ 3 $^{\rm o}$. This is perpendicular to the position angle of the disc of 48 $\pm$ 5 $^{\rm o}$ as deduced from millimeter imaging by Koerner & Sargent (1995). This finding is consistent, as scattering off the imaged millimeter disc is expected to yield a polarization signature in a direction that is rotated by 90 $^{\rm o}$ from this disc. The observed spectropolarimetric behaviour of RY Tau is reminiscent of that seen in a large group of Herbig Ae stars, suggesting a common circumstellar origin of the polarized photons.

Key words: stars: formation -- stars: pre-main sequence -- stars: individual: RY Tau -- stars: circumstellar matter -- techniques: polarimetric

Offprint request: J. S. Vink, j.vink@ic.ac.uk

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