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811.
Absolute masses for W Ursae Majoris and Algol-type close binaries can be determined from their parallax, if observed, and the relative sizes of the stars and their mass ratio, obtained from a light curve solution. An error propagation study compares the typical order of magnitude of the various terms involved, and shows how accurate parallaxes have to be in order to make the procedure work, i.e., making the parallax term not larger than the combined non-parallax terms, and producing reasonably low mass errors. Some comments are made on the possibilities with respect to the HIPPARCOS program.Communication presented at the International Conference on Astrometric Binaries, held on 13–15 June, 1984, at the Remeis-Sternwarte Bamberg, Germany, to commemorate the 200th anniversary of the birth of Friedrich Wilhelm Bessel (1784–1846). 相似文献
812.
A. Čadež 《Astrophysics and Space Science》1985,109(2):399-402
We respond to comments made in a recent letter by Karimet al. (1984), and show that the examples of interstellar absorption at2800 Å that they have presented so far can all be attributed to overexposure of the IUE detectors. 相似文献
813.
I. A. Issa 《Astrophysics and Space Science》1985,113(2):317-323
The size distribution of dark clouds and of H II regions were used to derive a distance of 440±22 kpc for M31. Some galactic H II regions and dark clouds were combined with the same ingredients in M31 to study the mass spectrum of both phenomena. A gas to dust ratio of 10001 has been derived for M31. Radii of the classical H II regions as derived in this work using distance of 440 kpc agrees with the galactic classical H II region radii. 相似文献
814.
Using observations obtained with the Clark Lake radioheliograph we determined the diameter of the Sun in the decameter wavelength range. Both equatorial and polar diameters increase with decreasing frequency, as D=Af
. The eccentricity of the brightness distribution appears to remain constant in the frequency range (30–74 MHz) in good agreement with the optical results in a corresponding height range. The smaller size of the polar diameter is attributed to coronal holes covering the poles during the period of our observations, while streamers were observed at the equator most of the time. 相似文献
815.
David R. Soderblom 《Icarus》1985,61(2):343-345
Knowledge of a star's rotation period and ν sin i can be used to select stars that are seen pole-on, and thus are well suited to planetary searches by astrometric or direct-imaging means. A table of such stars is presented. This method is not suitable for discriminating equator-on systems and so cannot be used to select candidates for the photometric method of W. J. Borucki and A. L. Summers (1984, Icarus58, 121–134). 相似文献
816.
R. A. Serafin 《Celestial Mechanics and Dynamical Astronomy》1985,36(3):273-280
We consider the collision probability for comets with the Sun under the suppositions of different velocity distributions and various initial conditions. We solve the problem applying Laplace's method and using Schiaparelli's hyperboloid of visibility. The probabilities obtained in this manner are given separately for elliptic and hyperbolic orbits. 相似文献
817.
C. Baixeras M. Casas F. Fernandez A. Vidal-Quadras M. Ortega 《Astrophysics and Space Science》1983,96(2):321-331
Elemental abundances of the VH group of cosmic radiation have been measured in the energy interval 250–550 MeV nucl–1 in a balloon exposure at Sioux Falls (South Dakota) of a plastic detector LeXAN stack. The so obtained abundances have been extrapolated to the sources in the frame of the homogeneous model correcting for energy loss. After taking into account solar modulation, the best fit to model values has led to a escape mean free path e = 5E
–0.4 g cm–2, whereE is the energy in GeV nucl–1, forE>1 GeV nucl–1, and a constant e = 5 g cm–2 forE1 GeV nucl–1. When turning to the diffusion model, also including an energy loss term, a diffusion coefficientD=3×1028 cm2 s–1 has been estimated. 相似文献
818.
Angle-averaged partial frequency redistributionR II has been employed in obtaining a simultaneous solution of radiative transfer equation in the comoving frame and the statistical equilibrium equation for a non-LTE two level atom. We have obtained the ratios of population densities of the upper and lower levels of the resonance line of PV by utilizing the data given in Bernacca and Bianchi (1979). Line source functions are also obtained for different types of variations of density and velocity of the expanding gases. We have considered the atmosphere to be 11 times as thick as the stellar radius. The first iteration was started by putting the density of the upper level (N 2) equal to zero. However, the convergent solution shows a substantial increase inN 2 although it is still much less than the equilibrium value. The line source function and the ratio of the densities of the particles in the upper and lower levels fall sharply from a maximum at τ=τmax to minimum at τ=0. We have studied the scattering integral \(\int {_{ - \infty }^{ + \infty } J_x \phi _x } dx\) and found that this quantity also varies quite similar to the ratioN 2/N 1 and the line source functionS L. 相似文献
819.
The effect of the Coriolis force on the Kelvin-Helmholtz instability has been investigated, in which basic velocities of fluid are varying slowly with lateral coordinatey. The problem is solved by J.W.K.B. approximation method. Parabolic and other types of profiles for wide long channel flow have also been studied in detail. 相似文献
820.
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