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UBC Theses and Dissertations

CCD photometry of NGC 3201 Brewer, James Philip


CCD observations of the halo globular cluster NGC 3201, acquired at the Dupont 2.5m telescope at Las Campanas, are reduced and analyzed. The data are from two separate observing runs. During the first run deep data were secured for a field at seven core radii from the centre, whilst during the second run, shallow data were secured for the central field of the cluster. Colour-magnitude diagrams are presented, and a two-colour diagram is constructed using data from the latter run. From the colour-magnitude diagram and colour-colour diagrams, estimates for reddening, metallicity, distance modulus and age are derived, and consistency with values in the literature is shown. Blue stragglers were observed in the central field, and are shown to be more centrally concentrated than subgiants in an equal magnitude interval. A UV bright star was observed in the central field, and magnitudes and colours are reported for it. The possible nature of this object is discussed. Mass functions were derived using deep V and I band data, by binning both on mass and on luminosity. Discrepancies between the two mass functions are discussed and resolved. The counts in a background field are compared to those expected from the Galactic model of Bahcall and Soneira (1980, 1984), and a discrepancy is found at fainter magnitudes. Mass-luminosity relationships (MLRs) in V and I were used to generate an isochrone which showed good agreement with the data, lending credence to the MLRs. Finally, the slope of the mass function is measured for stars with M < 0.4.M⊙, and values are obtained for the half-mass relaxation time and 'destruction time' of NGC 3201. These values show consistency with the results of Richer et al. (1991).

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