Abstract
We present Doppler imaging and Balmer line analysis of the weak-line T Tauri
star TWA 6. Using this data we have made one of the first attempts to measure
differential rotation in a T Tauri star, and the first detection of a slingshot
prominence in such a star. We also show the most direct evidence to date of the
existence of solar-type plages in a star other than the Sun.
Observations were made over six nights: 11-13th February 2006 and 18-20th
February 2006, when spectra were taken with the UCL Echelle Spectrograph on the
3.9-m Anglo-Australian Telescope. Using least-squares deconvolution to improve
the effective signal--to--noise ratio we produced two Doppler maps. These show
similar features to maps of other rapidly rotating T Tauri stars, i.e. a polar
spot with more spots extending out of it down to equator. Comparison of the two
maps was carried out to measure the differential rotation. Cross-correlation
and parameter fitting indicates that TWA 6 does not have detectable
differential rotation.
The Balmer emission of the star was studied. The mean H-alpha profile has a
narrow component consistent with rotational broadening and a broad component
extending out to 250km/s. The variability in H-alpha suggests that the
chromosphere has active regions that are cospatial with the spots in the
photosphere, similar to the 'plages' observed on the Sun. In addition the star
has at least one slingshot prominence 3 stellar radii above the surface - the
first such detection in a T Tauri star.
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