A model for the large amplitude QPO luminosity variation in the tail of SGR giant flares Academic Article uri icon

abstract

  • A model is presented for the quasiperiodic component of magnetar emission during the tail phase of giant flares. The model invokes modulation of the particle number density in the magnetosphere. The magnetospheric currents are modulated by torsional motion of the surface and we calculate that the amplitude of neutron star surface oscillation should be approximately 1% of the NS radius in order to produce the observed quasiperiodic luminosity variations. Using an axisymmetric analytical model for structure of the magnetosphere of an oscillating NS, we calculate the angular distribution of the optical depth to the resonant Compton scattering. The anisotropy of the optical depth may be why QPO are observed only at particular rotational phases.

publication date

  • January 1, 2008