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91.
Orbits based principally on radial-velocity measurements made with the Haute-Provence Coravel spectrometer are presented for
eight binary systems which include some of the faintest HD stars in the Galactic-Pole field. They are HD 103418 (which is
double-lined), 105021, 108151, 113169, 113323, 113650, 113714, and 116514. Their periods range from 3.7 to 15.1 days. Very
little else is known about any of them. 相似文献
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98.
A. Del Popolo 《Monthly notices of the Royal Astronomical Society》2001,325(3):1190-1196
I study the evolution of halo density profiles as a function of time in the SCDM and ΛCDM cosmologies. Following Del Popolo, I calculate the concentration parameter c = r v / a and study its time evolution. For a given halo mass, I find that c ( z ) ∝ 1/(1+ z ) in both the ΛCDM and SCDM cosmology, in agreement with the analytic model of Bullock et al. and N -body simulations. In both models, a ( z ) is roughly constant. The present model predicts a stronger evolution of c ( z ) with respect to the Navarro, Frenk & White model. Finally I show some consequences of the results on galaxy modelling. 相似文献
99.
A. R. King J. P. Osborne K. Schenker 《Monthly notices of the Royal Astronomical Society》2002,329(2):L43-L46
We show that the recently discovered short period supersoft source in M31 is probably a progenitor of a magnetic cataclysmic variable (CV). The white dwarf spins asynchronously because of the current high accretion rate. However its fieldstrength is typical of an AM Herculis system, which is what it will ultimately become. We discuss the relevance of this system to CV evolution, and its relation to some particular CVs with special characteristics. 相似文献
100.
R.J.R. Williams D. Ward-Thompson A.P. Whitworth 《Monthly notices of the Royal Astronomical Society》2001,327(3):788-798
We present hydrodynamical simulations of the formation, structure and evolution of photoionized columns, with parameters based on those observed in the Eagle Nebula. On the basis of these simulations we argue that there is no unequivocal evidence that the dense neutral clumps at heads of the columns were cores in the pre-existing molecular cloud. In our simulations, a variety of initial conditions leads to the formation and maintenance of near-equilibrium columns. Therefore, it is likely that narrow columns will often occur in regions with large-scale inhomogeneities, but that observations of such columns can tell us little about the processes by which they formed. The manner in which the columns in our simulations develop suggests that their evolution may result in extended sequences of radiation-induced star formation. 相似文献