Cool Stars 14 - Submitted Abstract # 64
This version created on 05 October 2006

Surface Differential Rotation and Convection Zone Depth


Stephen Marsden, ETH Zurich
Svetlana Berdyugina, ETH Zurich
Brad Carter, University of Southern Queensland
Jean-Francois Donati, LATT Observatoire Midi-Pyrenees
Matthew Mengel, University of Southern Queensland
Pascal Petit, LATT Observatoire Midi-Pyrenees

Differential rotation is believed to be one of the key mechanisms
driving the magnetic dynamos of active stars and the measurement of
surface differential rotation is one of the few ways we have to probe
the operation of such dynamos.  The surface differential rotation of
active stars can be measured though indirect imaging techniques such
as (Zeeman) Doppler imaging by the incorporation of a simplified
solar-like differential rotation law into the imaging process.  There
are now a growing number of active stars for which this has been done
and we can start to determine how the level of surface differential
rotation depends on basic stellar parameters and evolutionary state.
To extend the existing sample of stars with observed differential
rotation to higher masses (and shallower convection zones) we have
used Doppler imaging to determine the surface differential rotation of
early G and late F dwarfs.  We show that for dwarf stars there appears
to be a significantly steeper dependence on the depth of the stellar
convection zone than previously thought, with differential rotation
increasing dramatically for late F and early G dwarfs.  In addition,
using surface differential rotation measurements of giant and
sub-giant components of RS CVn stars we speculate that as a star
evolves off the main-sequence and the relative depth of the convection
zone increases then the level of differential rotation of the star
decreases.

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