Spectrophotometry of a Galaxy with UV-excess

We present the results of a spectral study of Galaxy No. 47 of the list [1]. We determine the equivalent widths of the lines for the compact part of the galaxy and the relative intensities for both the compact part and the halo. We estimate the mass of the galaxy from the inclination of the H line. We obtain the electron density and the mass of the gas component of the compact part of the galaxy.Translated fromAstrofizika, Vol. 38, No. 2, 1995.     

A study of some stars with circumstellar dust envelopes. I

We present the results of a study of circumstellar dust envelopes of 36 stars of early(O-B-A) types in the directions of the associations Cas OB1, Cas OB2, Per OB1, and Ori OB1. We determine the absorption at 1640 Å, the linear radius of the dust envelopes, the mean value of the coefficient k, and the masses of the envelopes. They differ significantly from one another.Translated fromAstrofizika, Vol. 38, No. 3, 1995.     

Dynamics of Mars-orbiting dust: Effects of light pressure and planetary oblateness

This paper deals with dynamics of impact ejecta from Phobos and Deimos initially on near-circular equatorial orbits around Mars. For particles emitted in a wide size regime of 1 micron and greater, and taking into account the typical particle lifetimes to be less than 100 years, the motion is governed by two perturbing forces: solar radiation pressure and influence of Mars' oblateness. The equations of motion of particles in Lagrangian non-singular elements are deduced and solved, both analytically and numerically, for different-sized ejecta. We state that the coupled effect of both forces above is essential so that on no account can the oblateness of Mars are be neglected. The dynamics of grains prove to be quite different for the ejecta of Phobos and Deimos. For Deimos, the qualitative results are relatively simple and imply oscillations of eccentricity and long-term variations of orbital inclination, with amplitudes and periods both depending on grain size. For Phobos, the dynamics are shown to be much more complicated, and we discuss it in detail. We have found an intriguous peculiar behavior of debris near 300 µm in size. Another finding is that almost all the Phobos ejecta with radii less than 30 µm (against the values of 5 to 20 µm adopted earlier by many authors) should be rapidly lost by collisions with martian surface. The results of the paper may be the base for constructing an improved model of dust belts that presumably exist around Mars.     

Signatures of solar wind interaction with the nightside ionosphere of Venus

Plasma and field relationships observed across the nightside of Venus evidence a chaotic variety of interactions between the ionosphere and the combined effect of the solar wind and interplanetary magnetic field draped about the planet. Close examination of these data reveal within the chaos a number of repeatable signatures key to understanding fundamental field-plasma interactions. Observed from the Pioneer Venus Orbiter, (PVO), nightside conditions range from extensive, full-up ionospheres with little evidence of dynamic or energetic perturbations, to an almost full depletion, sometimes described as disappearing ionospheres. Between these extremes, the ionospheric structure is often irregular, sometimes exhibiting well-defined density troughs, at other times complex intervals of either abundant or minimal plasma concentration. Consistently, large B-fields (typically exceeding 5–10 nanoteslas) coincide with plasma decreases, whereas stable, abundant plasma distributions are associated with very low-level field. We examine hundreds of nightside orbits, identifying close correlations between regions of elevated magnetic fields featuring polarity reversals, and (a) exclusive low-frequency or distinctive broadband noise, or both, in the electric field data, (b) turbulent, superthermal behavior of the the ions and electrons. We review extensive studies of nightside fields to show that the correlations observed are consistent with theoretical arguments that the presence of strong magnetic fields within normal ionospheric heights indicates the intrusion of magnetosheath fields and plasma within such regions. We find abundant evidence that the ionosphere is frequently disrupted by such events, exhibiting a chaotic, auroral-like complexity appearing over a wide range of altitude and local time. We show that field-plasma disturbances, widely suggested to be similar to conditions in the Earth's auroral regions, are tightly linked to the electric field noise otherwise attributed to lightning. Owing to the coincidence inherent in this relationship, we suggest that natural, predictable plasma instabilities associated with the plasma gradients and current sheets evident within these events produce the E-field noise. The data relationships argue for a more detailed investigation of solar wind induced E-field noise mechanisms as the appropriate scientific procedure for invoking sources for the noise previously attributed to lightning. Consistent with these views, we note that independent analyses have offered alternative explanations of the noise as arising from ionospheric disturbances, that repeated searches for optical evidence of lightning have found no such evidence, and that no accepted theoretical work has yet surfaced to support the inference of lightning at Venus.     

Thinking of England and taking care: family building strategies and infant mortality in England and Wales, 1891-1911

"Debates concerning the origins and development of the late nineteenth- to early twentieth-century declines in marital fertility and infant mortality in England and Wales have been centred largely on the material provided by answers to the ?special' questions in the 1911 census. In their published form these figures have restricted researchers to an examination of large scale geographic and social class differences in the levels and rates of decline of the two phenomena. This paper outlines research conducted on a sample of individual census returns from the 1911 census. From this data it becomes clear that for Victorian and Edwardian England ?where one lived' was rather more important than ?who one was' in determining both family building strategies and the survival of those children born."     

Multi-color coronographic imaging of the beta pictoris disk

In this paper we present multicolor images of the Beta Pictoris disk, obtained with a new Coronograph, built at STScI, for ESO's New Technology Telescope. These B, V, and R observations probe the Beta Pictoris circumstellar disk in to a distance of 35 AU (2) from the central star. We derive surface brightness profiles for the disk and discuss the results in the context of two-component disk models (e.g. Backmanet al. 1992), which are based on fits to available optical and infrared data for Beta Pictoris's disk. These models generally imply that the disk is composed of 1) an outer disk extending from 100–1000 AU, with a midplane particle density decreasing as n(r) r^–3, 2) a transition region extending from 10–100 AU with lower density and either smaller grains or a less steep spatial gradient than the outer component, 3) an innermost clear zone with even lower density.     

Colliding winds model of X-ray radiation in SS 433: analysis of X-ray eclipses

Interpretation of X-ray eclipses in SS 433 binary system in the framework of wind-wind collision model yields high value of mass ratioq =m _x /m _v > 1 which implies high mass of relativistic objectm _x > 8M .     

Phase transitions in the ISM a source of dissipative behaviour

By considering a simple fluid model, we investigate the role of phase transitions in the ISM on the galaxy- scale gas dynamics. Cooling and heating timescales in the ISM are typically shorter than typical galactic rotation timescales, so the individual phases in the ISM can be assumed to be in temperature equilibrium with the radiation field. Using this approximation we can construct an equation of state which depends upon the average density and mass fractions in the individual phases. Previous studies suggest that there is an equilibrium phase fraction as a function of pressure. We incorporate evolution towards this equilibrium state as a relaxation term with a time to obtain equilibrium . We derive a condition in terms of a critical Mach number when one dimensional shocks should be continuous. For small values of the relaxation time we show that the relaxation term acts like a viscosity. We show with one dimensional simulations that increasing causes shocks to become smoother. This work suggests that phase changes can strongly effect the gas dynamics of the ISM across spiral arms and bars.     

Accretion spin-up of low-magnetic neutron stars

The present paper is concerned with the spin-up of low-magnetic neutron stars by the accretion of matter onto the star. Calculations have been made for the evolution of the rotation of a neutron star and applied to different stellar models. It is shown that the existence of a millisecond pulsar imposes no restriction on any of the equations of state considered. However, constraints would arise with the possible discovery of third-octave pulsars (with frequencies in excess of 1000 Hz). Predictions are made as to the distribution of bursters over the orbital periods of neutron stars (about half of these having similar orbital periods). It is demonstrated that in the case of continued accretion onto a star, after it has acquired the critical angular frequency allowing no diviation from axial symmetry, specific accretion disks can be formed with a smooth transition into a star. The specific angular momentum is computed for a neutron star for the instant of the attainment of the Oppenheimer-Volkoff limit.     

Effects of rotation on Rayleigh-Taylor instabilities of an accelerating,compressible, perfectly conducting plane layer

The stability of a plane-stratified slab of perfectly conducting, rotating, compressible, inviscid plasma accelerated by a magnetic field is considered. Exact solutions for the growth rates of the unstable modes are determined for a -law gas when the undisturbed equilibrium is an isothermal atmosphere of semi-infinite extent with no frozen-in field. It is shown that the rotation has no effect on the region of unstable modes which has wavelengths long compared with the atmospheric scale height. On the other side, the growth rates in the presence of rotation are less than those in the absence of rotation for unstable modes.