Resolved polarization changes across Hα in the classical T Tauri star RY Tauri

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

Corresponding author: J. S. Vink, j.vink@ic.ac.uk

Received: 1 April 2003
Accepted: 3 June 2003

Abstract

We present linear Hα spectropolarimetry of the classical T Tauri star RY Tau. A change in the polarization percentage and position angle across Hα 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  diagram and find it to be 146 ± 3^o. This is perpendicular to the position angle of the disc of 48 ± 5^o  as deduced from millimeter imaging by Koerner & Sargent ([CITE]). 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^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.