Showing papers on "Mass segregation published in 1989"
TL;DR: In this paper, the authors examined the hypothesis that the blue stragglers in globular clusters are produced by physical stellar collisions and found that if a small fraction of the main-sequence stars in those systems are primordial binaries, then physical stellar collision can occur at the required rate of one every about 10 to the 8th year.
Abstract: The hypothesis that the blue stragglers in globular clusters are produced by physical stellar collisions is critically examined. The most serious objection to the collisional hypothesis is that direct stellar collisions between single stars are not expected to occur frequently enough in low-density globular clusters to account for the observed number of blue stragglers in such clusters. However, if a small fraction of the main-sequence stars in those systems are primordial binaries, then physical stellar collisions can occur at the required rate of one every about 10 to the 8th yr. This is because: (1) mass segregation will result in a high binary frequency in the cluster core; (2) the cross section for a binary-binary collision is about 100 times that for a single-single collision; and (3) physical stellar collisions are likely to occur during strong binary-binary interactions. Since a small fraction of binaries cannot be ruled out in the low-density globular clusters, then neither can the collisional hypothesis for the blue stragglers. Several observations that could be used to test the collisional hypothesis are listed. 52 refs.
186 citations
TL;DR: In this article, the main-sequence LFs are derived for three fields at different radial distances from the center of the globular cluster M30 and the observed radial dependence of the slope of the LF is compared with the predictions of mass segregation from the multi-mass component King (1966) models computed by Pryor et al.
Abstract: The main-sequence LFs are derived for three fields at different radial distances from the center of the globular cluster M30. It is found that the LFs become flatter with decreasing radius. The observed radial dependence of the slope of the LF is compared with the predictions of mass segregation from the multi-mass component King (1966) models computed by Pryor et al. (1986). The models are shown to be consistent within the errors with an equipartition model with a global mass function slope of x = 0.9, confirming the validity of the mass segregation corrections of Pryor et al. 24 refs.
50 citations
TL;DR: In this paper, star counts were carried out on V CCD frames of the globular cluster M71 and a systematic radial variation in the main-sequence luminosity function of the cluster was observed, clearly demonstrating that mass segregation is operative in the cluster.
Abstract: Star counts were carried out on V CCD frames of the globular cluster M71. A systematic radial variation in the main-sequence luminosity function of the cluster is observed, clearly demonstrating that mass segregation is operative in the cluster. The mass segregation predicted by an isotropic multimass King model is shown to be in good agreement with the present observations. The observations are consistent with those expected from a cluster undergoing dynamical relaxation. 27 refs.
23 citations
01 Jan 1989
2 citations
01 Jan 1989
TL;DR: In this article, color and population gradients in the cores of several highly concentrated globular clusters are reported, and the gradients are in the sense of blueing toward the cluster center, and appear to be caused mostly or entirely by population gradient in the number of blue horizontal branch and red giant branch stars.
Abstract: New observational results on color and population gradients in the cores of several highly concentrated globular clusters are reported. The gradients are in the sense of blueing toward the cluster center, and appear to be caused mostly or entirely by population gradients in the number of blue horizontal branch and red giant branch stars. Taken at face value, such gradients would imply an inverse mass segregation, but this interpretation is not fully secure. In any case, their dynamical understanding remains a problem.
2 citations
TL;DR: In this article, the mass segregation in the form of preferential concentration of more massive stars in the central regions of a number of open star clusters has been known for some time and the effects of stochastic fluctuations around the massive portion of the mass distribution function on the integrated colours should be taken into consideration, if they are present.
Abstract: Mass segregation in the form of preferential concentration of more massive stars in the central regions of a number of open star clusters has been known for some time. In this paper, integratedUBV colours in concentric zones have been estimated for 12 nearby open clusters using the observations of individual cluster members. It is found that the clusters showing pronounced mass segregation also show significant radial variations in the integrated colours. However, the effects of stochastic fluctuations around the massive portion of the mass distribution function on the integrated colours should be taken into consideration, if they are present.
1 citations