48 research outputs found
Unipolar Induction of a Magnetized Accretion Disk around a Black Hole
The structure and magnitude of the electromagnetic field produced by a
rotating accretion disk around a black hole were determined. The disk matter is
assumed to be a magnetized plasma with a frozenin poloidal magnetic field. The
vacuum approximation is used outside the disk.Comment: 7 pages, 1 figure
Possible observation sequences of Brans-Dicke wormholes
The purpose of this study is to investigate observational features of
Brans-Dicke wormholes in a case if they exist in our Universe. The energy flux
from accretion onto a Brans-Dicke wormhole and the so-called "maximum impact
parameter" are studied (the last one might allow to observe light sources
through a wormhole throat). The computed values were compared with the
corresponding ones for GR-wormholes and Schwarzschild black holes. We shown
that Brans-Dicke wormholes are quasi-Schwarzschild objects and should differ
from GR wormholes by about one order of magnitude in the accretion energy flux.Comment: 5 pages, 6 figure
Nearby low-mass triple system GJ795
We report the results of our optical speckle-interferometric observations of
the nearby triple system GJ795 performed with the 6-m BTA telescope with
diffraction-limited angular resolution. The three components of the system were
optically resolved for the first time. Position measurements allowed us to
determine the elements of the inner orbit of the triple system. We use the
measured magnitude differences to estimate the absolute magnitudes and spectral
types of the components of the triple: =7.310.08,
=8.660.10, =8.420.10, K5,
K9, K8. The total mass of the system is
equal to =1.69. We show
GJ795 to be a hierarchical triple system which satisfies the empirical
stability criteria.Comment: 6 pages, 2 figures, published in Astrophysical Bulleti
Spectroscopic analysis of the B/Be visual binary HR 1847
We studied both components of a slightly overlooked visual binary HR 1847
spectroscopically to determine its basic physical and orbital parameters. Basic
stellar parameters were determined by comparing synthetic spectra to the
observed echelle spectra, which cover both the optical and near-IR regions. New
observations of this system used the Ond\v{r}ejov and Rozhen 2-m telescopes and
their coud\'e spectrographs. Radial velocities from individual spectra were
measured and then analysed with the code {\FOTEL} to determine orbital
parameters. The spectroscopic orbit of HR 1847A is presented for the first
time. It is a single-lined spectroscopic binary with a B-type primary, a period
of 719.79 days, and a highly eccentric orbit with e=0.7. We confirmed that HR
1847B is a Be star. Its H\alpha emission significantly decreased from 2003 to
2008. Both components have a spectral type B7-8 and luminosity class IV-V.Comment: Astronomy and Astrophysics, accepte
A cyclic universe with colour fields
The topology of the universe is discussed in relation to the singularity
problem. We explore the possibility that the initial state of the universe
might have had a structure with 3-Klein bottle topology, which would lead to a
model of a nonsingular oscillating (cyclic) universe with a well-defined
boundary condition. The same topology is assumed to be intrinsic to the nature
of the hypothetical primitive constituents of matter (usually called preons)
giving rise to the observed variety of elementary particles. Some
phenomenological implications of this approach are also discussed.Comment: 21 pages, 9 figures; v.4: final versio
Approximated synthesis of antenna array for interference compensator
For the two-channel antenna array of interference compensator, consisting of the main antenna array and compensational antenna with low directivity, the problem of approximated synthesis of the main antenna array of isotropic radiators is solved, in which the radiation patters in the region of side lobes is formed, taking into account the radiation pattern of the compensational antenna