1996A&A...306..803J

The hypothesis that strong differential rotation coupled with the preferential appearance of higher latitude hot spots on classical T Tauri stars (CTTS) and low latitude cool spots on naked T Tauri stars (NTTS) can account for the apparent difference in the rotation periods of the two groups of stars is tested. It is shown that the required level of differential rotation produces measurable changes in the profile shapes of the photospheric absorption lines. High spectral resolution observations of 1 NTTS (HDE 283572; vsini≃110km/s) and 2 CTTS (SU Aur; vsini≃66km/s and RY Tau; vsini≃50km/s) are analyzed for the presence of differential rotation. It is shown that these stars are consistent with solid-body rotation and rule out the strong differential rotation required to explain the rotation period difference between CTTS and NTTS. This further supports the hypothesis that CTTS do in fact rotate slower than NTTS due to the interaction of stellar magnetic fields with the accretion disks which surround CTTS. In addition, a more accurate measure of vsini≃80km/s for HDE 283572 is given.