Optical structure of X-ray globular clusters

Journal Article · Fri Nov 01 04:00:00 EST 1985 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/163590· OSTI ID:5486182

Hertz, P; Grindlay, J E

CTIO 4-m prime-focus plates of eight globular clusters containing bright X-ray sources have been obtained. Plates in several colors (principally U and B) of each cluster have been digitized. A maximum symmetry method for determining the center of a globular cluster image is described and applied to each cluster in order to determine the cluster center with an accuracy of above 1.0 arc sec. Surface brightness profiles have been derived for seven clusters and fitted with King (1966, 1980) models to yield core radii within about 10 percent. These determinations of the cluster centers and core radii are sufficiently accurate to allow Grindlay et al. (1984) to statistically measure the mass of the globular cluster X-ray sources. Two clusters (NGC 6624 and M15) show significant excesses of light in their cores over the best-fit King model, in agreement with the results of Djorgovski and King (1984). The significance of these excesses, as well as the lack of any dependence of globular cluster structural parameters on color, is discussed. 44 references.

• Research Organization: E. O. Hulburt Center for Space Research, Washington, DC; Harvard-Smithsonian Center for Astrophysics, Cambridge, MA
• OSTI ID: 5486182
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 298; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640103* -- Astrophysics & Cosmology-- Quasi-Stellar
Radio
& X-Ray Sources-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMIC RAY SOURCES
COSMIC X-RAY SOURCES
DISTRIBUTION
ELECTROMAGNETIC RADIATION
MASS DISTRIBUTION
MATHEMATICAL MODELS
RADIATIONS
SPATIAL DISTRIBUTION
STAR CLUSTERS
VISIBLE RADIATION