Open AccessNeutron star asteroseismology. Axial crust oscillations in the Cowling approximation
Author(s) -
Samuelsson Lars,
Andersson Nils
Publication year - 2007
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2006.11147.x
Subject(s) - physics , neutron star , magnetar , crust , asteroseismology , astrophysics , radius , equation of state , geophysics , stars , quantum mechanics , computer security , computer science
Recent observations of quasi‐periodic oscillations in the aftermath of giant flares in soft gamma‐ray repeaters suggest a close coupling between the seismic motion of the crust after a major quake and the modes of oscillations in a magnetar. In this paper, we consider the purely elastic modes of oscillation in the crust of a neutron star in the relativistic Cowling approximation (disregarding any magnetic field). We determine the axial crust modes for a large set of stellar models, using a state‐of‐the‐art crust equation of state and a wide range of core masses and radii. We also devise useful approximate formulae for the mode‐frequencies. We show that the relative crust thickness is well described by a function of the compactness of the star and a parameter describing the compressibility of the crust only. Considering the observational data for SGR 1900+14 and SGR 1806−20, we demonstrate how our results can be used to constrain the mass and radius of an oscillating neutron star.