Modos r de oscilação em estrelas de neutrões

Tese dout., Física - Astrofísica, Universidade do Algarve, 2007

This thesis is devoted to the study of r-modes in neutron stars. Its aim is to determine the in°uence of di®erential rotation on the evolution of the r-mode insta- bility and on the detectability of gravitational waves from the r-mode. Di®erential rotation, as shown recently, is an unavoidable feature of nonlinear r-modes. We analyse the role played by this di®erential rotation on the evolution of the r-mode instability in newly-born neutron stars. We show that, due to the presence of dif- ferential rotation, the amplitude of the r-mode saturates in a natural way, whereas the angular velocity of the star decreases to values compatible with observational data. We also study the detectability of gravitational waves emitted by newly-born neutron stars, due to the r-mode instability, taking into account di®erential rotation. We show that the detectability of these waves depends crucially on the di®erential rotation associated to the r-mode instability. For small initial di®erential rotation, gravitational waves could be detected by the advanced laser interferometer detectors LIGO and Virgo, if the neutron star is located less than 20 Mpc away from Earth.

Faculdade de Ciências e Tecnologia ( FCT)