673 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
How is Binary Radio-Pulsars with Black Holes Population Rich?
Using "Scenario Machine" we have carried out population synthesis of radio
pulsar with black hole binaries (BH+Psr) in context of the most wide
assumptions about star mass loss during evolution, binary stars mass ratio
distribution, kick velocity and envelope mass lost during collapse. Our purpose
is to display that under any suppositional parameters of evolution scenario
BH+Psr population have to be abundant in Galaxy. It is shown that in the all
models including models evolved by Heger et al. (2002), Woosley et al. (2002),
Heger et al. (2003) expected number of the black holes paired with radio
pulsars is sufficient enough to discover such systems within the next few
years.Comment: 8 pages, 4 figures, accepted to MNRA
Population synthesis of gamma-ray bursts with precursor activity and the spinar paradigm
We study statistical properties of long gamma-ray bursts (GRBs) produced by
the collapsing cores of WR stars in binary systems. Fast rotation of the cores
enables a two-stage collapse scenario, implying the formation of a spinar-like
object. A burst produced by such a collapse consists of two pulses, whose
energy budget is enough to explain observed GRBs. We calculate models of spinar
evolution using results from a population synthesis of binary systems (done by
the `Scenario Machine') as initial parameters for the rotating massive cores.
Among the resulting bursts, events with the weaker first peak, namely,
precursor, are identified, and the precursor-to-main-pulse time separations
fully agree with the range of the observed values. The calculated fraction of
long GRBs with precursor (about 10 per cent of the total number of long GRBs)
and the durations of the main pulses are also consistent with observations.
Precursors with lead times greater by up to one order of magnitude than those
observed so far are expected to be about twice less numerous. Independently of
a GRB model assumed, we predict the existence of precursors that arrive up to
>~ 10^3 s in advance of the main events of GRBs.Comment: 11 pages, 9 figures; published versio
Magnesium-Containing Slurry as Technogenic Alternative Raw Material for Magnesium Oxychloride Cement
It has been shown experimentally that a waste of magnesium metal production is a realistic alternative to naturally occurring cement raw materials. The waste is the carnallite slurry forming during the chlorination stage. The slurry contains magnesium oxide (MgO) and magnesium chloride (MgCl2) in a mass ratio close to their optimal ratio when preparing Sorel cement. It is found that the magnesium oxide in the slurry is highly reactive. MgO extracted from the slurry and MgCl2 solution are mixed forming homogeneous magnesium oxychloride cement (MOC) paste in which bonding crystalline structures typical for Sorel cement are formed during hardening. © 2019 Published under licence by IOP Publishing Ltd
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
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