THE ACCURACY OF THE RELATIVISTIC COWLING APPROXIMATION

We investigate the accuracy of two versions of the relativistic Cowling approximation for the oscillations of general relativistic stellar models: one by McDermott, Van Horn and Scholl, and a refinement by Finn. The oscillation frequencies and the viscous damping time scales of several of the lowest frequency dipole p-modes in these approximations are compared to the exact values for these quantities. We find, as expected, that the accuracy of the Cowling approximation improves as the number of nodes in the eigenfunctions of the mode increases. Furthermore, the McDermott, Van Horn, and Scholl version of the Cowling approximation is more accurate than Finn's refined version for the low-order p-modes studied here.