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Showing papers on "Mass segregation published in 1990"


Journal ArticleDOI
TL;DR: The evolution of equal-mass star clusters containing a mass fraction of about 20 percent binaries has been followed using direct integration, making one run each for a total number of stars of N = 282 and N = 563, and four runs for N = 1126.
Abstract: The evolution of equal-mass star clusters containing a mass fraction of about 20 percent binaries has been followed using direct integration, making one run each for a total number of stars of N = 282 and N = 563, and four runs for N = 1126. For comparison the evolution of an equivalent star system where the binaries were replaced by stars twice as heavy as the other stars was followed. The pre-core-collapse evolution is driven by mass segregation between the equal-mass single stars and the binaries, which are twice as heavy. After core collapse, the cluster shows, on average, a smooth reexpansion driven by a steady rate of burning (hardening) of primordial binaries. With so much primordial fuel present, the postcollapse cluster core is significantly larger than is the case in comparison runs without primordial binaries. 64 refs.

77 citations


Journal ArticleDOI
TL;DR: In this paper, the authors examined various transport processes which may have affected the chemical homogeneity in protocluster clouds and showed that the characteristic diffusion time scale associated with collisions between grains and gas atoms is considerably longer than that on which star formation is expected to occur.
Abstract: Various transport processes which may have affected the chemical homogeneity in protocluster clouds are examined. It is shown that the characteristic diffusion time scale associated with collisions between grains and gas atoms is considerably longer than that on which star formation is expected to occur. Collisions between large grains and gas atoms lead to mass segregation and metallicity gradients on a time scale comparable to the crossing time of the clusters in the Galaxy. One possible mechanism for inducing and maintaining chemical homogeneity is turbulent diffusion in the clouds. The mixing time scale required in this case is comparable to several internal dynamical time scales, longer than the evolutionary time scale of the most massive stars, and shorter than the Galactic orbital time scale of the clouds. Thus, metals in presently observed stars probably did not originate from upper main-sequence stars of a coeval generation.

21 citations