Limits on the Differential Rotation of T Tauri Stars
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**Session 48 -- Young Stars**
*Display presentation, Tuesday, 10, 1995, 9:20am - 6:30pm*

## [48.05] Limits on the Differential Rotation of T Tauri Stars

*C.M. Johns (McDonald Observatory, The University of Texas at Austin)*

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 small but measurable changes in the profile
shapes of the photospheric absorption lines. High spectral resolution
observations of 1 NTTS (HDE 283572 - $v$sin$i \approx 110$ km s$^{-1}$) and 2
CTTS (SU Aur - $v$sin$i \approx 65$ km s$^{-1}$; RY Tau - $v$sin$i \approx 50$
km s$^{-1}$) 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 $v$sin$i \approx 80$ km s$^{-1}$ for
HDE 283572 is given.

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