79 research outputs found
Vibration Powered Radiation of Quaking Magnetar
In juxtaposition with the standard model of rotation powered pulsar, the
model of vibration powered magnetar undergoing quake-induced torsional Alfven
vibrations in its own ultra strong magnetic field experiencing decay is
considered. The presented line of argument suggests that gradual decrease of
frequencies (lengthening of periods) of long-periodic pulsed radiation detected
from a set of X-ray sources can be attributed to magnetic-field-decay induced
energy conversion from seismic vibrations to magneto-dipole radiation of
quaking magnetar.Comment: Text of talk presented at "Mini-Workshop on Pulsars", Nov. 12th,
2010; KIAA-PKU, Beijin
Alfven seismic vibrations of crustal solid-state plasma in quaking paramagnetic neutron star
Magneto-solid-mechanical model of two-component, core-crust, paramagnetic
neutron star responding to quake-induced perturbation by differentially
rotational, torsional, oscillations of crustal electron-nuclear solid-state
plasma about axis of magnetic field frozen in the immobile paramagnetic core is
developed. Particular attention is given to the node-free torsional
crust-against-core vibrations under combined action of Lorentz magnetic and
Hooke's elastic forces; the damping is attributed to Newtonian force of shear
viscose stresses in crustal solid-state plasma. The spectral formulae for the
frequency and lifetime of this toroidal mode are derived in analytic form and
discussed in the context of quasi-periodic oscillations of the X-ray outburst
flux from quaking magnetars. The application of obtained theoretical spectra to
modal analysis of available data on frequencies of oscillating outburst
emission suggests that detected variability is the manifestation of crustal
Alfven's seismic vibrations restored by Lorentz force of magnetic field
stresses.Comment: 10 pages, 10 figure
Radiative activity of magnetic white dwarf undergoing Lorentz-force-driven torsional vibrations
We study radiative activity of magnetic white dwarf undergoing torsional
vibrations about axis of its own dipole magnetic moment under the action of
Lorentz restoring force. It is shown that pulsating white dwarf can convert its
vibration energy into the energy of magneto-dipole emission, oscillating with
the frequency equal to the frequency of Alfv\'en torsional vibrations, provided
that internal magnetic field is decayed. The most conspicuous feature of the
vibration energy powered radiation in question is the lengthening of periods of
oscillating emission; the rate of period elongation is determined by the rate
magnetic field decay.Comment: Mod. Phys. Lett. A 26 (2011) 359-36
Torsional nodeless vibrations of quaking neutron star restored by combined forces of shear elastic and magnetic field stresses
Within the framework of Newtonian magneto-solid-mechanics, relying on
equations appropriate for a perfectly conducting elastic continuous medium
threaded by a uniform magnetic field, the asteroseismic model of a neutron star
undergoing axisymmetric global torsional nodeless vibrations under the combined
action of Hooke's elastic and Lorentz magnetic forces is considered with
emphasis on a toroidal Alfv\'en mode of differentially rotational vibrations
about the dipole magnetic moment axis of the star. The obtained spectral
equation for frequency is applied to -pole identification of
quasi-periodic oscillations (QPOs) of X-ray flux during the giant flares of SGR
1806-20 and SGR 1900+14. Our calculations suggest that detected QPOs can be
consistently interpreted, within the framework of this model, as produced by
global torsional nodeless vibrations of quaking magnetar if they are considered
to be restored by the joint action of bulk forces of shear elastic and magnetic
field stresses.Comment: 18 pages, 5 figures; accepted in Ap
Elasticity of nuclear medium as a principal macrodynamical promoter of electric dipole pygmy resonance
Motivated by arguments of the nuclear core-layer model formulated in [S.I.
Bastrukov, J.A. Maruhn, Z.Phys. A 335 (1990) 139], the macroscopic excitation
mechanism of electric pygmy dipole resonance (PDR) is considered as owing its
origin to perturbation-induced effective decomposition of nucleus into two
spherical domains - undisturbed inner region treated as static core and
dynamical layer undergoing elastic shear vibrations. The focus is placed on the
imprinted in the core-layer model mechanism of emergence of the low-energy
dipole electric resonant excitation as Goldstone soft mode of translation
layer-against-core oscillations. To accentuate this attitude we regain the
obtained in the above paper spectral equation for the frequency of spheroidal
elastic vibrations trapped in the finite-depth layer, but by working from
canonical equation of elastic dynamics of continuous medium. The obtained
analytic equations for the frequency of dipole vibrational state in question
and its excitation strength exhibit fundamental character of this soft dipole
mode of nuclear resonant response.Comment: Accepted in Phys.Lett.
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