438 research outputs found
Spinar Paradigm and Gamma Ray Bursts Central Engine
A spinar is a quasi-equilibrium collapsing object whose equilibrium is
maintained by the balance of centrifugal and gravitational forces and whose
evolution is determined by its magnetic field. The spinar quasi equilibrium
model recently discussed as the course for extralong X-ray plateu in GRB
(Lipunov & Gorbovskoy, 2007). We propose a simple non stationary
three-parameter collapse model with the determining role of rotation and
magnetic field in this paper. The input parameters of the theory are the mass,
angular momentum, and magnetic field of the collapsar. The model includes
approximate description of the following effects: centrifugal force,
relativistic effects of the Kerr metrics, pressure of nuclear matter,
dissipation of angular momentum due to magnetic field, decrease of the dipole
magnetic moment due to compression and general-relativity effects (the black
hole has no hare), neutrino cooling, time dilatation, and gravitational
redshift. The model describes the temporal behavior of the central engine and
demonstrates the qualitative variety of the types of such behavior in nature.
We apply our approach to explain the observed features of gamma-ray bursts of
all types. In particular, the model allows the phenomena of precursors, x-ray
and optical bursts, and the appearance of a plateau on time scales of several
thousand seconds to be unified.Comment: 17 pages, 16-figures, MNRAS in prin
Galactic Binary Gravitational Wave Noise within LISA Frequency Band
Gravitational wave noise associated with unresolved binary stars in the
Galaxy is studied with the special aim of determining the upper frequency at
which it stops to contribute at the rms noise level of the proposed space-born
interferometer (LISA). The upper limit to this background is derived from the
statistics of SN Ia explosions, part of which can be triggered by binary white
dwarf coalescences. The upper limiting frequency at which binary stochastic
noise crosses LISA rms sensitivity is found to lie within the range 0.03-0.07
Hz, depending on the galactic binary white dwarf coalescence rate. To be
reliably detectable by LISA, the energy density of relic cosmological
background per logarithmic frequency interval should be
Omega_{GW}h_{100}^2>10^{-8} at f>0.03 Hz.Comment: 16 pages with 1 eps figure, aasms4.sty, to appear in the ApJ vol. 494
February 20, 1998 issu
Neutron star spin-kick velocity correlation effect on binary neutron star coalescence rates and spin-orbit misalignment of the components
We study the effect of the neutron star spin -- kick velocity alignment
observed in young radio pulsars on the coalescence rate of binary neutron
stars. Two scenarios of the neutron star formation are considered: when the
kick is always present and when it is small or absent if a neutron star is
formed in a binary system due to electron-capture degenerate core collapse. The
effect is shown to be especially strong for large kick amplitudes and tight
alignments, reducing the expected galactic rate of binary neutron star
coalescences compared to calculations with randomly directed kicks. The
spin-kick correlation also leads to a much narrower NS spin-orbit misalignment.Comment: 7 pages, 5 figures, accepted for publiction in MNRA
Trans-sonic propeller stage
We follow the approach used by Davies and Pringle (1981) and discuss the
trans-sonic substage of the propeller regime. This substage is intermediate
between the supersonic and subsonic propeller substages. In the trans-sonic
regime an envelope around a magnetosphere of a neutron star passes through a
kind of a reorganization process. The envelope in this regime consists of two
parts. In the bottom one turbulent motions are subsonic. Then at some distance
the turbulent velocity becomes equal to the sound velocity.
During this substage the boundary propagates outwards till it
reaches the outer boundary, and so the subsonic regime starts.
We found that the trans-sonic substage is unstable, so the transition between
supersonic and subsonic substages proceeds on the dynamical time scale. For
realistic parameters this time is in the range from weeks to years.Comment: 8 pages with figures, submitted to Astron. Astroph. Transaction
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