Towards probing the internal angular momentum distribution in red giants from solar-like oscillations

As red giants show very low surface velocities, rotational splitting has not been detected so far in their comb-like structure from solar-like oscillations. We propose to study the rotational splitting of l=3 modes to discriminate between the competing effects of rotational splitting and finite mode lifetime. Modes of different radial orders probe different depth. The information of rotational splitting with respect to the radial order could lead to an estimate of the magnitude of differential rotation inside their convective layers. This is a first attempt to measure the magnitude of the differential rotation in these evolved stars. An extensive spectroscopic multi-site campaign to study solar-like oscillations in two promising targets, gamma Psc and theta1 Tau is being set up for the second half of 2010. The observational result will be confronted with state-of-the-art models. Independent from the outcome on differential rotation, strong constraints on the models of re!

d giants will be set. gamma Psc and theta1 Tau will provide an optimal case to test the underlying physics.