Physics
Scientific paper
Aug 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006iaujd...8e..52m&link_type=abstract
Solar and Stellar Activity Cycles, 26th meeting of the IAU, Joint Discussion 8, 17-18 August 2006, Prague, Czech Republic, JD08,
Physics
Scientific paper
The surface differential rotation of a star can be measured mainly in two ways, through the analysis of the Fourier transforms of a star's line profiles or through spot evolution from Doppler imaging maps. Measurements of differential rotation on early-G and later type stars, using the Doppler imaging technique, shows an increase in differential rotation with stellar mass, however this increase is not sufficient to account for the high levels of differential rotation observed on F-stars using line profile analysis. This difference was thought to be possibly the result of studying two different types of stars, active spotted stars with Doppler imaging and non-active stars with line profile analysis. Using the Doppler imaging technique we have determined the surface differential rotation of two active spotted late-F dwarfs. Both of these stars show a high level of surface differential rotation well above that of later-type stars measured with the same technique but of a similar level to that measured on F-stars using line profile analysis. These results show that the level of surface differential rotation on active stars increases far more dramatically with stellar mass than previously thought from Doppler imaging results and indicates that there may not be a significant difference in the level of surface differential rotation for active and non-active stars. In addition, one of the F-dwarfs has been observed in circularly polarised light and the magnetic field has been reconstructed using Zeeman Doppler Imaging. This star shows a difference in the surface differential rotation measured from spots to that from magnetic features. This has previously been observed on K-dwarfs, however for our F-dwarf the surface differential rotation measured from spots is higher than that measured from magnetic features, the opposite of what is seen for K-dwarfs. Does this imply a change in the magnetic dynamo for the higher-mass star?
Carter Brad D.
Donati Jean-Francois
Marsden Stephen C.
Mengel Matthew W.
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