CHANGE IN ANGULAR VELOCITY OF PERTURBED GALACTIC BARS

The effect of tidal perturbations on the angular velocity of a barred galaxy is studied. Previous results indicating that the sign of this e ffect may depend on the perturber mass are confirmed. We study the cha nges in the parameters of the bar produced by the perturbation. Wherea s the bar will always lose angular momentum in the interaction, it may either gain or lose mass depending on the position angle of the peric entre of the perturber. The induced mass exchange between the bar and the disc is significant only above a threshold in the perturbation str ength. We propose that the total change in angular velocity results fr om a combination of the effects due to changes in mass and angular mom entum.