Showing papers in "Astrophysics and Space Science in 1982"

The 5 March 1979 event and the distinct class of short gamma bursts: are they of the same origin?

Abstract: A comparison of the 5 March 1979 event and other short gamma-ray bursts reveals considerable similarities in their features. This implies their common origin.

Study of physical properties of spectroscopic binary stars

Abstract: The main results of a study of a catalogue of physical parameters of 1041 spectroscopic binaries are presented. The distribution of spectroscopic binaries over all main parametersM1, a, e, M1/M2, P, and certain dependencies between some of them have been found. (1) It appears that among bright (mv≲3m–5m) stars withM≳1M⊙, about 40% are apparently spectroscopic binaries with comparable masses of components. (2) The majority of spectroscopic binaries with the ratio of the large semiaxis of the orbit to the radius of the primarya/R1≲20, have eccentricities close to zero. This is probably a consequence of the tidal circularization of orbits of close binaries by viscous friction. (3) The discovery of duplicity of double-line spectroscopic binaries is possible only if the semiamplitude of radial velocityK1 is almost 10 times higher than the semiamplitude of the radial velocity of a single-line spectroscopic binary of the same mass. (4) Double-line spectroscopic binaries witha/R⊙≲6(M1/M⊙)1/3,M1≈M2≳1.5M⊙ are almost almost absent, and the number of stars witha/R⊙≲6(M1/M⊙)1/3,M1≈1.5M⊙ is relatively low. (5) The distribution of unevolved SB stars over the large semiaxis may be described by the expression d(Nd/Nt)≈0.2 d loga for 6(M1/M⊙)1/3≲a/R⊙≲100. (6) The intial mass-function for primaries of spectroscopic binaries is the same Salpeter function dNd≈M1−2.35dM1 for 1≲M1/M⊙≲30. (7) It is possible to explain the observed ratio of the number of single-line spectroscopic binaries to the number of double-line binaries if one assumes that the average initial mass ratio is close to 1 and that the mass of the postmass-exchange remnant of the primary exceeds the theoretical one and/or that half of the angular momentum of the system is lost during mass-exchange. (8) The above-mentioned distributions ofM1 anda and assumptions on the mass of remnant and/or momentum loss also allow us to explain the observed shapes of dN/dM, dN/dq, and dN/da distributions after some selection effects are taken into account.

Equilibrium of a static charged perfect fluid sphere

Abstract: A study is developed for treating Einstein-Maxwell's equations, applied to a static perfect fluid sphere with charge, in a such a manner to generalize the Oppenheimer and Volkoff hydrostatic equilibrium equation.

Multimode stellar pulsations

Abstract: We apply the two time method to weakly anharmonic (nonlinear) stellar pulsations. The problem contains two small parameters: e-the ratio of the dynamical and the thermal timescale and μ-the measure of the anharmonicity in the oscillator equation. The 0(ɛ0) system is solved up to 0(μ) by the use of an asymptotic perturbation method. This solution is then used within the framework of the two time method to obtain the slow evolution of the amplitudes and entropy. Both monomode and double-mode pulsations are treated in a non-resonance case.

The heavy element yields of neutron capture nucleosynthesis

Abstract: Consideration of the contribution made to the abundances of the heavy element isotopes by the S- and R-processes of nucleosynthesis has led to the determination that the previous assumption concerning the exclusive alignment of isobars to one or the other of these processes is probably in error. If the relatively small odd and even mass number abundance fluctuations characterizing R-process abundances are always the case, as assumed by this study, S-process contributions to the abundances of R-process isobars are substantial, consistent with transient flashing episodes in the S-process neutron production processes. A smooth and monotonically-decreasing curve of the abundance of the S-process yields times the neutron capture cross-section versus mass number is therefore the primary tool for the separation of the abundances due to the two processes.

Radiation from a strongly-magnetized plasma: The case of predominant scattering

Abstract: On the basis of diffusion approach for normal modes, solutions of the radiative transfer problem are obtained and analysed for an optically thick tenuous plasma with a strong magnetic field. The case is considered when the scattering processes without change of photon frequency ω are dominant. The radiative transfer coefficients as well as spectra, angular dependences and polarization of the outgoing radiation are investigated in detail for a ‘cold’ plasma,kTe≩mc2, |ω−sωB|≫ωkTe/mc2 )1/2|cosϑ|, whereTe is the electron plasma temperature,ωB=eB/mc the electron cyclotron frequency,s=1,2,... the number of cyclotron harmonic and ϑ the angle between the magnetic field and wave vector. The effects of electronpositron vacuum polarization are taken into account and shown to be very significant. Simple analytic solutions are obtained for various limiting cases (small and large vacuum polarization; high, low and close to the cyclotron resonance radiation frequencies; different orientations of the magnetic field, etc). The results obtained are necessary for analysing X-ray and gamma-ray radiation from strongly magnetized neutron stars.

Cosmic gamma-ray burst spectroscopy

Abstract: A review is given of the gamma-ray burst energy spectrum measurements on Venera 11 and Venera 12 space probes The gamma burst continuum approximates in shape thermal brems-strahlung emission of a hot plasma The radiation temperature varies over a broad range, 50–1000 keV, for different events Spectra of many bursts contain cyclotron absorption and/or redshifted annihilation lines Strong variability is typically observed in both continuum and line spectra These spectral data provide convincing evidence for the gamma-ray bursts being generated by neutron stars with superstrong magnetic fields ∼1012–1013 G

Resonant wave acceleration of minor ions in the solar wind

Abstract: This paper extends some previous work on the acceleration of minor ions in the solar wind to include the effects of wave acceleration and heating arising from minor ions interacting via the gyroresonance with ion cyclotron waves. Resonant wave acceleration is made up of two contributions, the first, and generally the more important, is a ‘local’ acceleration which is proportional to the wave power and the number of resonant particles and is also sensitive to the details of the distribution function; while the other contribution is basically ‘fluid dynamic’ in character, arises from the inhomogeneity of the medium and is proportional to the radial gradient of the resonant wave power. Under suitable cir-cumstances both contributions exhibit the feature that heavier ions receive greater acceleration than lighter ones. Also the kinematics of the resonance shows that the resonance wave acceleration switches off above a maximum differential speed, between ions and protons, which increases with increasing ratio of mass to charge. We also examine briefly possible beam instabilities driven by the streaming of minor ions relative to protons.

On the physics of relativistic double layers

Abstract: A model of a strong, time-independent, and relativistic double layer is studied. Besides double layers having the electric field parallel to the current the model also describes a certain type of oblique double layers. The ‘Langmuir condition’ (ratio of ion current density to electron current density) as well as an expression for the potential drop of the double layer are derived. Furthermore, the distributions of charged particles, electric field, and potential within the double layer are clarified and discussed. It is found that the properties of relativistic double layers differ substantially from the properties of corresponding non-relativistic double layers.

The influence of a net charge on the critical mass of a neutron star

Abstract: We derived the set of equations determining the structure of a spherically symmetric charged star within the framework of general relativity (modified Oppenhiemer-Volkoff equations). The equations have been solved for a completely degenerate Fermi gas with a charge density assumed to be proportional to the matter density. It is shown that the presence of a net charge does not affect the existence of a critical mass. The value, however, could be substantially altered, in some cases doubled.

Thermal and electrical conductivities of crystals in neutron stars and degenerate dwarfs

Abstract: Thermal and electrical conductivities due to electron scattering on phonons are calculated for degenerate cores of white dwarfs and envelopes of neutron stars for wide ranges of density, temperature and ion charge. In the stellar zones, in which T ≳ ħωpi(Z1/3e2/ħυF) (ωpiis the ion plasma frequency and υF the Fermi velocity of electrons), the main contribution into scattering comes from the Umklapp processes. In the zones with lowerT, the Umklapp processes are frozen out, that results in a sharp growth of electrical and thermal conductivities. This, for instance, should make nuclear burning more stable in such zones.

Spectrum of the Galactic Magnetic Fields

Abstract: The magnetic fields observed in the galactic disc are generated by the differential rotation and the helical turbulent motions of interstellar gas. On the scalesl=2πk−1 which lie in the intervall0

Ring nebulae associated with of stars: Statistics, classification, origin

Abstract: The ring nebulae associated with galactic Of stars is considered on the grounds of the list of Of nebulae proposed by lozinskaya and Lomovsky (1982). Taking into account the selection effects, about 80% of Of stars are shown to be associated withHii regions and about 30–50% of these regions have shell structures. Four types of nebulae associated with Of stars are resolved: amorphousHii regions, ring-likeHii regions, wind-blown bubbles, and stellar ejectas. These types appear to be identical to the morphology of nebulae around WR stars proposed by Chu (1981). Observational data are presented and the nature of a number of Of ring nebulae of different types is discussed.

Tilted electromagnetic Bianchi type III cosmological solution

Abstract: An exact cosmological solution to the Einstein-Maxwell equations for the case of Bianchi type III symmetry with ‘stiff’ matter and an electromagnetic field is constructed. The behaviour of the solution near the singularity and at late stages of the expansion is investigated.

MHD free-convection flow in the Stokes problem for a porous vertical plate.

Abstract: The effect of a uniform transverse magnetic field on the free-convection flow of an electrically-conducting fluid past an infinite, vertical, porous plate for both classes of impulsive as well as uniformly-accelerated motion of the plate is discussed. The magnetic lines of force are assumed to be fixed relative to the plate. Expressions for the velocity field and skin friction for both cases are obtained by the Laplace transform technique. The influence of the various parameters, entering into the problem, on the velocity field and skin-friction is extensively discussed with the help of graphs and tables.

General covariance, Accelerated frames and the particle concept

Abstract: The definition of particle states in various accelerated frames is considered It is shown that in any realistically accelerated system, quantum field theory can be formulated without any ambiguity We further show that the definition of a particle based on Green's function techniques does not always agree with the definition based on explicit quantization We analyse the standard accelerated detector results from this point of view and show that the uncertainty principle imposes a rigorous bound on these detection processes

Organo-siliceous biomolecules and the infrared spectrum of the Trapezium nebula

Abstract: A close correspondence exists between the infrared properties of a mixed culture of diatoms and the infrared spectrum of dust in the Trapezium nebula. We argue that this correspondence points to a cosmic microbiological system in which organo-siliceous polymers are an abundant constituent. The high content of Si relative to Mg found in the Earth's crust and in Lunar and Martian surface material is readily explained on the basis of accretion of silicon-rich microbiology.

Models of pulsating low-massive yellow supergiants

Abstract: The nonlinear self-excited oscillations of the envelopes of low-massive highly luminous stars are described. The parameters for these models wereM=0.8M⊙,Mbol=−5.5, −5.84 mag,Teff=4500, 5000, 5500 K. The oscillations have been found to consist of the standing wave pulsation near the envelope bottom and running waves in outer layers. The ratio of the standing wave frequency ω s to the average frequency of the running waves ω r increases with the stellar luminosity: ω s /ω r =1.7 whenMbol=−5.5 mag and ω s /ω r =2.4 whenMbol=−5.84 mag. The frequency of oscillations near the photosphere is found to be in close agreement with the critical frequency for running waves. Mass loss from these stars is caused by shocks. It has been shown that agreement between FG Sge's period change observed during the last decade and the period-luminosity relation for double shell stars takes place when FG Sge's luminosity isMbol=−5.96 mag.

The relaxation time of a one-dimensional self-gravitating system

Abstract: A computer experiment on a one-dimensional self-gravitating system is described We attempt to observe the dynamic time required for this system to thermalize by comparing the position and velocity densities with those predicted by the microcanonical ensemble Hohl and Broaddus (1967) have previously reported an estimate of the thermalization time which is inferred from studies of the kinetic energy covariance We ran the system for the time which they report and find that the system has not thermalized Furthermore, there is no evidence that the system is even proceeding towards equilibrium in the time-scale considered here Significant changes in the distribution do occur in a short time, after which the system remains in a stationary state which is not characteristic of equilibrium

On the direction of rotation of the spirals in galaxies.

Abstract: The detection of trailing arms in twenty spiral galaxies, completed by the 60s, allowed one to suggest the overwhelming prevalence of this sense of rotation. Pasha and Dambis (1982) have recently determined the direction of rotation in a further 54 galaxies and found two leading spirals, NGC 4490 and NGC 5395. The current sample of galaxies with an established sense of rotation contains 79 trailing and two leading systems. The two spirals found to be leading belong to M51′ type galaxies.

The Gravitational Instability of Flow Through Porous Medium for Some Systems of Astrophysical Interest

Abstract: The gravitational instability of flow through porous medium for some hydrodynamical and hydromagnetical systems of astrophysical interest is investigated. The effects of rotation, magnetic field, viscosity and finite electrical conductivity are studied for the gravitational instability through porous medium. The effect of suspended particles on the instability is also considered. It is found that Jean's criterion remains unchanged in the presence of porosity, viscosity, finite conductivity, rotation, magnetic field and suspended particles in the medium.

Towards a unification of the parameters underlying elementary particles and cosmology

Abstract: It is pointed out that the gross parameters characterizing the Universe such as the overall size and mass can be arrived at from microphysical considerations involving the fundamental interactions of elementary particle physics. Interesting relations for the Hubble radius and closure density are obtained in terms of the coupling constants underlying these interactions.

Infrared Spectroscopy over the 2.9–3.9 μm Waveband in Biochemistry and Astronomy

Abstract: The infrared spectrum of the galactic centre source GC-IRS 7 over the 2.9-3.9 μm waveband is interpreted as strong evidence for bacterial grains.

Computation of the elements of eclipsing binary systems in the frequency-domain

Abstract: The aim of the present paper will be to translate the essential parts of the theory of Fourier analysis of the light changes of eclipsing variables into more practical terms; and describe procedures (illustrated by numerical examples) which should enable their users to obtain the desired results with maximum accuracy and minimum loss of information by processes which can be fully automated.

Solutions of the spherically-symmetric cosmic-ray transport equation in interplanetary space

Abstract: Numerical solutions of the well-known spherically-symmetric transport equation for interstellar cosmic rays in the interplanetary medium are presented. It is shown: (a) why nuclei and electron modulations differ, (b) that it is easy to read more in the model than it contains, (c) that the only significant parameter that determines the level of modulation is the product of the solar wind speed and the number of diffusion mean free paths between observer and boundary, and (d) that observations do exist which cannot be explained in terms of this simple model.

A Self-Similar Flow in Generalized Roche Model with Increasing Energy

Abstract: The self-similar flow of a gas, moving under the gravitational attraction of a central body of fixed mass behind a spherical shock wave driven out by a propelling contact surface into quiet solar wind region, is investigated. The total energy content between the inner expanding surface and the shock front increases with time. In the last section we briefly pose the self-similar isothermal flow of a gas behind a spherical shock wave.

The HEAO-3 Cosmic Ray Isotope spectrometer

Abstract: This paper describes the Cosmic Ray Isotope instrument launched aboard the HEAO-3 satellite on September 20, 1979. The primary purpose of the experiment is to measure the isotopic composition of cosmic ray nuclei from Be-7 to Fe-58 over the energy range 0.5 to 7 GeV/nucleon. In addition charge spectra will be measured between beryllium and tin over the energy range 0.5 to 25 GeV/nucleon. The charge and isotope abundances measured by the experiment provide essential information needed to further our understanding of the origin and propagation of high energy cosmic rays. The instrument consists of 5 Cerenkov counters, a 4 element neon flash tube hodoscope and a time-of-flight system. The determination of charge and energy for each particle is based on the multiple Cerenkov technique and the mass determination will be based upon a statistical analysis of particle trajectories in the geomagnetic field.

Mid- and far-infrared extinction coefficients of hydrous silicate minerals

Abstract: Extinction coefficients were measured for three kind of hydrous silicate minerals, montmorillonite, chlorite and serpentine, from 7 to 140 μm. The infrared extinction coefficients of these minerals show (1) a few broad bands in the mid-infrared region and (2) a less steep wavelength-dependence in the far-infrared region, in contrast to those of high-temperature magnesium silicates. In the far-infrared region, montmorillonite shows a λ−0.8±0.1 dependence (λ, the wavelength) without any band structure, chlorite has a double maxima structure around 80 μm, and serpentine shows a rather steep dependence with a small peak at 77 μm.

The universal diagram for magnetized neutron stars in the galaxy

Abstract: A convenient diagram for an analysis of astrophysical appearances and evolution of magnetized neutron stars has been proposed. The diagram gives a general approach to such different objects as radiopulsars, X-ray pulsars, gamma-ray bursters, the SS 433 source, and others.

Monte-carlo simulations of galaxy systems

Abstract: Computer models of galaxy fields are generated using the Monte-Carlo simulation technique described in Paper I (MacGillivrayet al., 1982b). In the models, various scenarios for the true 3-dimensional distribution of galaxies (e.g., clustering on continuous or hierarchical scales) are incorporated and the galaxies projected onto a synthetic photographic plate. All factors affecting the light from distant galaxies are taken into account in the simulations and also factors affecting the detection and measurement of faint galaxy images on photographic plates scanned with an automatic plate-measuring machine. The model fields are compared, both qualitatively and statistically, with a field obtained from measures with COSMOS on a deep photograph taken with the UK Schmidt Telescope. The results indicate that the observed distribution of faint galaxies on photographic plates can only be represented by a model involving second order clustering of galaxies. However, the exact nature of this second-order clustering cannot be unambiguously ascertained from the 2-D distributions, both a uniformly-populated supercluster model and the cellular model being able to represent statistically the observed projected distribution of galaxies.