A $BVI$ Photometric Study of the Near-Galactic Center Globular Cluster NGC 6517 (C1759-089)

Abstract

We present the results of a $BVI$ photometric study of the globular cluster NGC 6517 using CCD images obtained at the prime focus of the CFHT. From the resultant color-magnitude diagram, we infer that the cluster is differentially reddened and develop a method for determining the amplitude of this effect, which amounts to \( \sim 0.4 \) mag in \( (V-I) \) across our $\sim 4$ arc-min field. From the corrected $V_0,$ $(V-I{)}_0$ color-magnitude diagram, we derive the metallicity and distance modulus of the cluster. Our values for the mean foreground reddening ($E(B-V)=1.10\pm 0.10$) and metallicity (\feh\ = -1.58 $\pm$ 0.05) agree to within uncertainties with previous determinations. Our apparent distance modulus of 18.3 $\pm$ 0.2, however, is larger than the sole previous determination. When the distance modulus is corrected for absorption, assuming that $R_V=3.8$ for this line of sight, we find that NGC 6517 is within 3 kpc of the Galactic center, making it a bulge member. This makes NGC 6517 only the fourth metal poor cluster in the bulge for which an accurate CMD is available.

arXiv commentSubmitted as a uuencoded gziped tar file containing tex document and macros. Also available via ftp://astro.queensu.ca/pub/ngc6517.ps or http://astro.queensu.ca/~kauelaar/ngc6517.html

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