Photometric observations of CH Cygni in the period 1978–1987. Dust matter condensation in its circumstellar envelope during 1985–1987     

O. G. Taranova  B. F. Yudin 《Astrophysics and Space Science》1988,146(1):33-39

We present the results of the photometric observations, in theUBVRJHKLMNQ system, of CH Cyg, made in the period 1978–1987. They have shown that from 1985 to 1987 dust condensed in its circumstellar envelope have taken place the condensation of the dust matter. In 1987 its mass and temperature were about 3×10^–8 M and 800 K, respectively.  相似文献   

A new approach to the possibilities of Σ(D)-dependence and distances of the supernova remnants     

A. O. Allakhverdiyev  O. H. Guseinov  F. K. Kasumov  I. M. Yusifov 《Astrophysics and Space Science》1986,121(1):21-44

A new way of choosing of the calibrators for constructing (D)-dependence of supernova remnants (SNR) is suggested. A knowledge of the distance of an SNR is not sufficient to consider it as a calibrator. It is shown that neither more accurate determination of distance to calibrators, nor an increase in their number, nor an increase in the precision of the remnant angular size and radio flux determination can lead to a considerable improvement of simple (D)-dependence which is suggested in the given work.For remnants with small surface brightnesses there is no (D)-dependence at all. The most accurate remnant distances currently known, are given: these are liable to change only after a large amount of additional observational data accurately compiled.  相似文献   

Dynamical effects of dark matter in systems of galaxies     

J. F. Navarro  D. Garcia Lambas  J. L. Sérsic 《Astrophysics and Space Science》1986,123(1):117-123

SeveralN-body experiments were performed in order to simulate the dynamical behaviour of systems of galaxies gravitationally dominated by a massive dark background.We discuss mass estimates from the dynamics of the luminous component (M _VT) under the influence of such a background, assuming a constant dark/luminous mass ratio (M _D/M _L) and plausible physical conditions. We extend in this way previous studies (Smith, 1980, 1984) about the dependence ofM _VT on the relative distributions of dark and luminous matter (Limber, 1959). We found that the observed ratio of the virial theorem mass to luminosity (M _VT/L) in systems of galaxies of different sizes could be the result of different stages of their post-virialisation evolution as was previously suggested by White and Rees (1978) and Barnes (1983). This evolution is mainly the result of the dynamical friction that dark matter exerts on the luminous component. Thus our results give support to the idea that compact groups of galaxies are dynamically more evolved than large clusters, which is expected from the hierarchical clustering picture for the formation of such structures.  相似文献   

Isovortical orbits in uniformly rotating coordinates     

Michael E. Hough 《Celestial Mechanics and Dynamical Astronomy》1986,39(3):249-266

For the conservative, two degree-of-freedom system with autonomous potential functionV(x,y) in rotating coordinates; $$\dot u - 2n\upsilon = V_x , \dot \upsilon + 2nu = V_y $$ , vorticity (v _x -u _y ) is constant along the orbit when the relative velocity field is divergence-free such that: $$u(x,y,t) = \psi _y , \upsilon (x,y,t) = - \psi _x $$ . Unlike isoenergetic reduction using the Jacobi, integral and eliminating the time,non-singular reduction from fourth to second-order occurs when (u,v) are determined explicitly as functions of their arguments by solving for ψ (x, y, t). The orbit function ψ satisfies a second-order, non-linear partial differential equation of the Monge Ampere type: $$2(\psi _{xx} \psi _{yy} - \psi _{xy}^2 ) - 2(\psi _{xx} + \psi _{yy} ) + V_{xx} + V_{yy} = 0$$ . Isovortical orbits in the rotating frame arenot level curves of ψ because it contains time explicitly due to coriolis effects. Rather, (x, y) coordinates along the orbit are obtained, from (u, v) either by numerical integration of the kinematic equations, or by partial differentiation of the Legendre transform ? of ψ. In the latter case, ? is shown to satisfy a non-linear, second-order partial differential equation in three independent variables, derived from the Monge-Ampere Equation. Complete reduction to quadrature is possible when space-time symmetries exist, as in the case of central force motion.  相似文献   

Polarimetry of comets: A review     

Dobrovolsky  O. V.  Kiselev  N. N.  Chernova  G. P. 《Earth, Moon, and Planets》1986,34(2):189-200

Some attempts of polarimetric sounding of Comet Halley will be undertaken from the flyby probes. In order to facilitate the final planning and the future interpretation of these experiments we have done a thorough analysis of practically all available polarimetric observations. An emphasis is made on interpretation attempts and their discussion. The results of the phase dependence of polarization investigations are presented covering a wide range of phase angles . The chief peculiarities of this dependence are: maximum polarization at = 90, diminishing through zero at 20, negative values up to several per cent and a final growth to zero at zero . A division into gaseous and dusty comets on polarimetric basis is revealed. The wavelength dependence of polarization is discussed. The numerous results of detailed polarimetry are compared to the negative results of attempts to detect the elliptical polarization. New observational problems arising from the evidence given by the negative polarization at small phase angles and by the opposition effect recently discovered are discussed.  相似文献   

The magnetic and thermodynamical structure of a coronal hole     

Vladimir A. Osherovich  Erast B. Gliner  Israel Tzur  Michael L. Kuhn 《Solar physics》1985,97(2):251-266

A nonpolytropic model of a polar coronal hole at 2 R R 5 R is constructed. Our main assumptions are: (1) the magnetic structure of the Sun can be described by a combination of dipole-like and radial fields; (2) in the magnetically dominated region [(v ²/2) < (B ²/8)] the influence of the outflow on the magnetic structure is negligible. The magnetic and thermodynamic structures are obtained by solving the force balance equation for plasma with the observationally derived electron density. Profiles of velocities in the acceleration regime are presented and the influence of the outflow on the thermodynamic structure of the solar corona above the polar region is discussed.This paper is the first part of a joint project of the Space Environment Laboratory, the Joint Institute for Laboratory Astrophysics, and the High Altitude Observatory, NCAR. The second paper by Munro and Tzur is in preparation.Work done while at the Space Environment Laboratory, NOAA, ERL, Boulder, CO 80303, U.S.A.1982–83 Visiting Fellow at the Joint Institute for Laboratory Astrophysics, National Bureau of Standards and University of Colorado.The National Center for Atmospheric Research is sponsored by the National Science Foundation.Visitor at NCAR.  相似文献   

The impact of migration on the spatial structure of rural settlement     

Shirgazin OR 《Soviet geography》1983,24(9):684-694

"Changes in the system of settlement in Staraya Russa Rayon, Novgorod Oblast [USSR], are traced. Migration from peripheral areas of the rayon to the suburban zone of Staraya Russa and to larger inhabited places along highways has transformed the historical pattern of settlement focused on river valleys into a new pattern focused on the central city of Staraya Russa, i.e., from the traditional dendritic configuration into a monocentric pattern. The impact of the migration process on land use is discussed, and it is suggested that abandoned peripheral villages be converted to recreation uses."  相似文献   

A versatile ground data display system for spacelab experiments     

Dan Werthimer  Beth Keer  Michael Lampton 《Astrophysics and Space Science》1983,95(1):21-36

We describe a microprocessor-based data capture and display system suited to the needs of many Spacelab experimenters. Although developed specifically for the needs of the FAUST ultraviolet astronomy telescope, several features of the system may make it attractive to other groups who need to interact with their Spacelab data in real or near-real time. The display system captures data from the serial data stream originating in the Spacelab experiment computer input/output (ECIO) data channel, and can reformat and display several hundred variables per second in real time. The system offers a combination of Cathode Ray Tube (CRT) display and analog paper strip-chart output. A facility is also provided for simultaneously creating floppy-disk records of short segments of data according to prearranged criteria, to allow detailed examination of critical events in the operation of the experiment. The simplicity, economy, reliability, and flexibility of the display system suggest its use for monitoring a variety of low- and medium-data-rate Spacelab experiments.  相似文献   

Variability of carbon monoxide in the mars atmosphere     

R.T. Clancy  D.O. Muhleman  B.M. Jakosky 《Icarus》1983,55(2):282-301

In January of 1982 we measured a microwave spectrum of CO in the Martian atmosphere utilizing the rotational J = 1 → 2 transition of CO. We have analyzed data and reanalyzed the microwave spectra of R. K. Kakar, J. W. Waters, and W. J. Wilson, (Science196, 1090–1091, 1977, measured in 1975) and J. C. Good and F. P. Schloerb, (Icarus47, 166–172, 1981 measured in 1980) in order to constrain estimates of the temporal variability of CO abundance in the Martian atmosphere. Our values of CO column density from the data of Karar et al., Good and Schloerb, and our own are 1.7 ± 0.9 × 10²⁰, 3.0 ± 1.0 × 10²⁰, and 4.6 ± 2.0 × 10²⁰cm^?2, respectively. The most recent estimate of CO column density from the 1967 infrared spectra of J. Connes, P. Connes, and J.P. Maillard, (Atlas de Spectres Infarouges de Venus, Mars, Jupiter, et Saturne, Editions due Centre National de la Recherche Scientifique, Paris, 1969), is 2.0 ± 0.8 × 10²⁰ cm^?2 (L.D.G. Young and A.T. Young, Icarus30, 75–79, 1977). The large uncertainties given for the microwave measurements are due primarily to uncertainty in the difference between the continuum brightness temperature and atmospheric temperatures of Mars. We have accurately calculated the variation among the observations of the continuum (surface) brightness temperature of Mars, which is primaroly a function of the observed aspect of Mars. A more difficult problem to consider is variability of global atmospheric temperatures among the observations, particularly the effects of global dust storms and the ellipticity of the orbit of Mars. The large bars accompanying our estimates of CO column density from the three sets of microwave measurements are primarily caused by an assumed uncertainty of ±10°K in our atmospheric temperature model due to possible dust in the atmosphere. A qualitative consideration of seasonal variability of global atmospheric temperatures among the measurements suggests that there is not strong evidence for variability of the column abundance of CO on Mars, although variability of 0–100% over a time scale of several years is allowed by the data set. The implication for the variability of Mars O₂ is, crudely, a factor of two less. We found that the altitude distribution of CO in the atmosphere of Mars was not well constrained by any of the spectra, although our spectrum was marginally better fitted by an altitude increasing profile of CO mixing ratios.  相似文献   

Distinct climate change synchronous with Heinrich event one, recorded by stable oxygen and carbon isotopic compositions in stalagmites from China   总被引：2，自引：0，他引：2  

Houyun Zhou  Jianxin Zhao  Michael K. Gagan  Jun Yan 《Quaternary Research》2008,69(2):306-315

Uranium-series dating of oxygen and carbon isotope records for stalagmite SJ3 collected in Songjia Cave, central China, shows significant variation in past climate and environment during the period 20-10 ka. Stalagmite SJ3 is located more than 1000 km inland of the coastal Hulu Cave in East China and more than 700 km north of the Dongge Cave in Southwest China and, despite minor differences, displays a clear first-order similarity with the Hulu and Dongge records. The coldest climatic phase since the Last Glacial Maximum, which is associated with the Heinrich Event 1 in the North Atlantic region, was clearly recorded in SJ3 between 17.6 and 14.5 ka, in good agreement in timing, duration and extent with the records from Hulu and Dongge caves and the Greenland ice core. The results indicate that there have been synchronous and significant climatic changes across monsoonal China and strong teleconnections between the North Atlantic and East Asia regions during the period 20-10 ka. This is much different from the Holocene Optimum which shows a time shift of more than several thousands years from southeast coastal to inland China. It is likely that temperature change at northern high latitudes during glacial periods exerts stronger influence on the Asian summer monsoon relative to insolation and appears to be capable of perturbing large-scale atmospheric/oceanic circulation patterns in the Northern Hemisphere and thus monsoonal rainfall and paleovegetation in East Asia. Climatic signals in the North Atlantic region propagate rapidly to East Asia during glacial periods by influencing the winter land-sea temperature contrast in the East Asian monsoon region.  相似文献