CCD PHOTOMETRY IN THE GLOBULAR-CLUSTER NGC-3201

CCD Photometry in U, B, V and I is presented for the halo globular clu ster NGC 3201. The data analyzed consist of CCD images of two fields, one being centered on the cluster core and the other located at approx imately 7 core radii. Images were secured in U, B, and V for the ''cor e'' field and B, V, and I for the ''outer'' field. In addition, images of a nearby background field were secured in V and I. The fiducial se quence of NGC 3201, derived from the color-magnitude diagram of the co re field, was compared to that of NGC 362 and it was found that the cl usters are approximately coeval. The core field revealed a sequence of 31 blue stragglers which were shown, by means of a Kolomogorov-Smirno v test, not to be more centrally concentrated than subgiants of the sa me V magnitude range. By means of incompleteness tests, it was found t hat the blue straggler sample is more than 95% complete. Luminosity fu nctions in V and I were derived using photometry from the outer field and background field. Mass-luminosity relationships (MLRs) in V and I were used to generate an isochrone, which was compared with the cluste r color-magnitude diagram. The morphologies were found to be similar, lending credence to the V and I MLRs. Mass functions for the outer fie ld in NGC 3201 were derived using both V and I data. The mass function based on the I-band measures was found to rise sharply at low masses, having an exponent of x = 2.0+/-0.3 for stars with M < 0.4M.. The mas s function exponent for low-mass stars and a rough estimate of the tim e it will take NGC 3201 to disrupt were found to fit the emerging patt ern between these two parameters.