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Marek J. Sarna Sinan K. Yerli & Alexander G. Muslimov 《Monthly notices of the Royal Astronomical Society》1998,297(3):760-768
We examine the possibility of probing dynamo action in mass-losing stars, components of Algol-type binaries. Our analysis is based on the calculation of non-conservative evolution of these systems. We model the systems U Sge and β Per where the more massive companion fills its Roche lobe at the main sequence (case AB) and where it has a small helium core (early case B) respectively. We show that to maintain evolution of these systems at the late stages which are presumably driven by stellar 'magnetic braking', an efficient mechanism for producing large-scale surface magnetic fields in the donor star is needed. We discuss the relevance of dynamo operation in the donor star to the accelerated mass transfer during the late stages of evolution of Algol-type binaries. We suggest that the observed X-ray activity in Algol-type systems may be a good indicator of their evolutionary status and internal structure of the mass-losing stellar components. 相似文献
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D.K. Nourgaliev R.Kh. Muslimov N.N. Sidorova I.N. Plotnikova 《Journal of Geochemical Exploration》2006,89(1-3):293
Changes in oil composition in the course of the development depend on numerous factors including both technogenic and natural ones. Physicochemical compositional analysis of 2456 oil samples collected in the Romashkino field in 1982–2000 from two productive strata (Devonian and Carboniferous reservoirs) has indicated statistically significant variations in the i-butane to n-butane content ratio (i-b / n-b). This ratio is characterized not only by a trend of steady growth but also by a significant variation with a period of 4.5 years. The i-b / n-b ratio variations are well correlated (R2 = 0.61) between these two reservoirs (Devonian and Carboniferous) occurring at different depths. However, the average i-b / n-b ratios recorded in these reservoirs are essentially different (0.44 and 0.55, respectively). A possible relationship is discussed between the i-b / n-b ratio variations and those in global seismicity. 相似文献
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The resonant excitation of the large-scale nonradial oscillations of a star by turbulent convection is considered. In the case of an incompressible inhomogeneous liquid sphere and a spherical shell we have demonstrated the excitation of oscillations and have obtained the explicit analytic expressions for the oscillation amplitudes. The effect of uniform axial rotation of a star upon the oscillations has also been considered. The estimates of the r.m.s. velocities of the excited quadrupole oscillations based on solar parameters do not contradict the observations of the 160 min. solar oscillations. Results are briefly discussed and applications are also made to the case of nonradial oscillations of outer convection zones of white dwarfs, Jupiter and Saturn. 相似文献
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Exact analytic expressions for the vacuum electromagnetic fields produced by an oscillating magnetized sphere are obtained. The solutions are analysed for various modes of pulsation and for low-order multipole magnetic moments. Within the context of neutron star oscillations, the possibility of gamma-ray generation is discussed. It is shown that the radial pulsations provide an efficient mechanism for generation of gamma-radiation and electron-positron pairs in some regions around the neutron star. For this, the non-vanishing quadrupole magnetic moment oblique to the dipole moment is required. The model for gamma-ray bursts that we propose is briefly considered. 相似文献
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A new picture of pulsar high-energy emission is proposed that is different from both the traditional polar cap and outer gap
models, but combines elements of each. The slot gap model is based on electron acceleration along the edge of the open field
region from the neutron star surface to near the light cylinder and thus could form a physical basis for the two-pole caustic
model of Dyks and Rudak (2003). Along the last open field line, the pair formation front rises to very high altitude forming
a slot gap, where the accelerating electric field is unscreened by pairs. The resulting radiation features both hollow cones
from the lower-altitude pair cascades, seen at small viewing angles, as well as caustic emission on the trailing-edge field
lines at high altitude, seen from both poles at large viewing angle. The combination of the small solid angle of slot gap
emission (≪ 1 sr) with a high probability of viewing the emission predicts that more gamma-ray pulsars could be detected at
larger distances. In this picture, many of the positional coincidences of radio pulsars with unidentified EGRET sources become
plausible as real associations, as the flux predicted by the slot gap model for many of the pulsars would provide the observed
EGRET source flux. The expected probability of seeing radio-quiet gamma-ray pulsars in this model will also be discussed. 相似文献
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We present Chandra X-ray observations of the Hydra A cluster of galaxies, and we report the discovery of structure in the central 80 kpc of the cluster's X-ray-emitting gas. The most remarkable structures are depressions in the X-ray surface brightness, approximately 25-35 kpc in diameter, that are coincident with Hydra A's radio lobes. The depressions are nearly devoid of X-ray-emitting gas, and there is no evidence for shock-heated gas surrounding the radio lobes. We suggest that the gas within the surface brightness depressions was displaced as the radio lobes expanded subsonically, leaving cavities in the hot atmosphere. The gas temperature declines from 4 keV at 70 kpc to 3 keV in the inner 20 kpc of the brightest cluster galaxy (BCG), and the cooling time of the gas is approximately 600 Myr in the inner 10 kpc. These properties are consistent with the presence of an approximately 34 M middle dot in circle yr-1 cooling flow within a 70 kpc radius. Bright X-ray emission is present in the BCG surrounding a recently accreted disk of nebular emission and young stars. The star formation rate is commensurate with the cooling rate of the hot gas within the volume of the disk, although the sink for the material that may be cooling at larger radii remains elusive. A bright, unresolved X-ray source is present in the BCG's nucleus, coincident with the radio core. Its X-ray spectrum is consistent with a power law absorbed by a foreground NH approximately 4x1022 cm-2 column of hydrogen. This column is roughly consistent with the hydrogen column seen in absorption toward the less, similar24 pc diameter VLBA radio source. Apart from the point source, no evidence for excess X-ray absorption above the Galactic column is found. 相似文献
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We adopt that in the interior of neutron stars both the proton and neutron superfluids are in the vortex state. Thus, in the superconducting core the magnetic field is expected to be organized in the form of quantized fluxoids. It is shown that fluxoids are buoyant. This gives rise to a rapid (5×104 yr) expulsion of the magnetic field out of the superconducting core to the subcrustal region, and a subsequent decay within the outer crust. The effect considered may be the physical reason why the characteristic decay-time of pulsar magnetic fields (106 yr) corresponds to the ohmic dissipation time within the neutron star crust. The intersection of two types of vortex lines with each other and its possible consequence for pulsars is briefly discussed. 相似文献
9.
E. R. Muslimov N. K. Pavlycheva G. G. Valyavin S. N. Fabrika 《Astrophysical Bulletin》2016,71(3):357-365
We present a new scheme of a moderate-resolution spectrograph based on a cascade of serial holographic gratings each of which produces an individual spectrum with a resolution of about 6000 and a bandwidth of 80 nm. The gratings ensure centering of each part of the spectrum they produce so as to provide uniform coverage of the broadest possible wavelength interval. In this study we manage to simultaneously cover the 430–680 nm interval without gaps using three gratings. Efficiency of the spectrograph optical system itself from the entrance slit to the CCD detector is typically of about 60% with a maximum of 75%. We discuss the advantages and drawbacks of the new spectrograph scheme as well as the astrophysical tasks for which the instrument can be used. 相似文献
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