STAR COUNTS, BLUE STRAGGLERS, AND MASS SEGREGATION IN NGC-7492

被引:37
作者
COTE, P
RICHER, HB
FAHLMAN, GG
机构
[1] MCMASTER UNIV,DEPT PHYS & ASTRON,HAMILTON L8S 4M1,ONTARIO,CANADA
[2] CANADA FRANCE HAWAII TELESCOPE CORP,KAMUELA,HI
关键词
D O I
10.1086/115961
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
New B, V photometry of the sparse globular cluster NGC 7492 is used to construct the cluster color-magnitude diagram (CMD) down to about three magnitudes below the main-sequence turnoff. Adopting a reddening of E(B - V) = 0.00 mag, we confirm the cluster metallicity to be [Fe/H] = - 1.51. The relative-age technique of VandenBerg et al. [AJ, 100, 445 (1990)] implies that NGC 7492 is approximately 1.7 +/- 1.2 Gyr older than NGC 6752. A distance modulus of (m - M)0 = 17.09 +/- 0.20 mag has been derived by comparing the NGC 6752 fiducial given in VandenBerg et al. to the NGC 7492 fiducial and adopting (m - M)0 = 13.17 +/- 0.17 mag for NGC 6752. We also report the discovery of 27 candidate blue stragglers which are found to be more centrally concentrated than the cluster subgiants of similar brightness. If mass segregation has occurred in the cluster, this result suggests that the blue stragglers are more massive than the stars at the main-sequence turnoff. A total of 3331 stars brighter than V = 24.0 mag have been counted in ten concentric annuli centered on the cluster core. There is no evidence for mass segregation in either the surface density profiles or in the luminosity functions at different radial positions. This is not unexpected since the stellar mass range sampled by the data is quite small, M approximately 0.80-0.60 M.. A comparison of the observed and theoretical luminosity functions suggests that the power-law index of the mass function is x = 0.1 +/- 0.5.
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页码:1358 / 1370
页数:13
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