by
DrLars Samuelsson(University of Southampton/School of Mathematics)
→
Europe/Stockholm
Nordita Seminar Room
Nordita Seminar Room
Description
Recent observations of quasi normal oscillations in the tail of the X-
ray signal from giant flares in soft gamma-ray repeaters (SGRs) has
sparked great interest among the neutron star community. This is not
surprising since the observed frequencies are consistent with seismic
motion in the crust of a neutron star. Should this interpretation indeed
hold true, the observations will be the first direct evidence of a
vibrating neutron star and will open the window to a seismological
deduction of the interiors of these extreme objects. This in turn will
constrain the illusive strong nuclear interactions.
The SGRs are believed to be described by a branch of neutron star models
referred to as magnetars due to the enormous magnetic fields prevailing
in them. In fact, the time for an Alfvén wave to cross the magnetar is
comparable to an oscillation period of the seismic waves in the crust
implying that the modes, if associated with the star, must be of a
global MHD type. Why then are the frequencies observed so close to the
purely elastic crustal modes?
In this talk I will present, by means of a series of toy-models, how
this puzzle can be resolved, and furthermore indicate how the
observations can be used to constrain the global structure of the
oscillating star.
