22 research outputs found
On Hoyle-Narlikar-Wheeler mechanism of vibration energy powered magneto-dipole emission of neutron stars
We revisit the well-known Hoyle-Narlikar-Wheeler proposition that neutron
star emerging in the magnetic-flux-conserving process of core-collapse
supernova can convert the stored energy of Alfven vibrations into power of
magneto-dipole radiation. We show that the necessary requirement for the energy
conversion is the decay of internal magnetic field. In this case the loss of
vibration energy of the star causes its vibration period, equal to period of
pulsating emission, to lengthen at a rate proportional to the rate of magnetic
field decay. These prediction of the model of vibration powered neutron star
are discussed in juxtaposition with data on pulsating emission of magnetars
whose radiative activity is generally associated with the decay of ultra strong
magnetic field.Comment: Accepted for publication in Astrophysics & Space Scienc
Alfven node-free vibrations of white dwarf in the model of solid star with toroidal magnetic field
In the context of the white dwarf asteroseismology, we investigate
vibrational properties of a non-convective solid star with an axisymmetric
purely toroidal intrinsic magnetic field of two different shapes. Focus is laid
on regime of node-free global Lorentz-force-driven vibrations about symmetry
axis at which material displacements have one and the same form as those for
nodeless spheroidal and torsional vibrations restored by Hooke's force of
elastic shear stresses. Particular attention is given to the even-parity
poloidal Alfven modes whose frequency spectra are computed in analytic form
showing how the purely toroidal magnetic fields completely buried beneath the
star surface can manifest itself in seismic vibrations of non-magnetic white
dwarfs. The obtained spectral formulae are discussed in juxtaposition with
those for Alfven modes in the solid star model with the poloidal, homogeneous
internal and dipolar external, magnetic field whose inferences are relevant to
Alfven vibrations in magnetic white dwarfs.Comment: Accepted for publication in Astrophysics & Space Scienc
Pairing effects in low density domain of nuclear matter
Using equations, governing np pairing correlations in S=1, T=0 pairing
channel (PRC 63 (2001) 021304(R)), it is shown that at low densities equations
for the energy gap in the spectrum of quasiparticles and chemical potentials of
protons and neutrons allow solutions with negative chemical potential. This
corresponds to appearance of Bose--Einstein condensate (BEC) of deuterons in
low density region of nuclear matter.Comment: 4 pages, 3 figure
Frequency spectrum of toroidal Alfv\'en mode in a neutron star with Ferraro's form of nonhomogeneous poloidal magnetic field
Using the energy variational method of magneto-solid-mechanical theory of a
perfectly conducting elastic medium threaded by magnetic field, the frequency
spectrum of Lorentz-force-driven global torsional nodeless vibrations of a
neutron star with Ferraro's form of axisymmetric poloidal nonhomogeneous
internal and dipole-like external magnetic field is obtained and compared with
that for this toroidal Alfv\'en mode in a neutron star with homogeneous
internal and dipolar external magnetic field. The relevance of considered
asteroseismic models to quasi-periodic oscillations of the X-ray flux during
the ultra powerful outbursts of SGR 1806-20 and SGR 1900+14 is discussed.Comment: Accepted for publication in Astrophysics & Space Scienc
The low-lying isoscalar giant dipole resonance
This short note is aimed to comment on the recently observed
low component of the isoscalar giant dipole resonance in connection
with the theoretical predictions made by microscopic and
hydrodynamical models