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K. von Braun, M. Mateo (Univ. of Michigan)
We present updated photometry results of our extensive monitoring project of the Galactic globular cluster NGC 3201, carried out at Las Campanas Observatory between June 1996 and May 1998. NGC 3201 is one of approximately 15 globular clusters (GCs) we are probing for the existence of eclipsing binary systems for which we will perform subsequent spectroscopic observations. The combination of photometric and spectroscopic data can provide estimates for the masses of the individual binary components as well as the distance to the cluster.
NGC 3201 is a low-latitude cluster (b ~ 8.6 deg) and strongly exhibits the effects of differential reddening across the field of the GC. In order to obtain high-quality, reliable photometry for the stars in the cluster, we created a internal differential reddening map for NGC 3201. This procedure involved finding the average offset along the reddening vector in the color-magnitude-diagram (CMD) between stars in a fiducial region in the cluster (no or very little differential reddening, i.e., the main sequence appears tight) and stars in the approximately 480 subregions covering our field of view.
We present the reddening map described above and compare it with the results from the extinction maps recently published by Schlegel et al (ApJ, 500, 525), along with the dereddened, deep-photometry CMD for NGC 3201, comprised of over 90 V and I images of the cluster. In addition, we show photometric lightcurves for approximately 8 eclipsing binary star candidates and give our estimates of the periods of these variables as well as their cluster membership.
The author(s) of this abstract have provided an email address for comments about the abstract: kaspar@astro.lsa.umich.edu