JHK PHOTOMETRY OF BRIGHT GIANTS IN M69

We discuss broadband near-infrared photometric measurements of bright giants in the metal-rich globular cluster M69 (NGC 6637), obtained with the University of Hawaii Institute for Astronomy 256 x 256 infrared camera at the Canada-France-Hawaii Telescope. Two fields were observed: one centered on the cluster nucleus, the other offset 50 arcsec north. Numerical experiments indicate that the internal accuracy of our photometry is comparable to that which can be achieved at optical wavelengths with CCD detectors. Adopting E(B - V) = 0.17, we find that the giant branch locus of M69 agrees well with that of 47 Tuc and, assuming an age of 13 Gyr, a comparison with theoretical isochrones predicts that [Fe/H] approximately - 0.7 - 0.2 + 0.1 for both clusters. The M69 horizontal branch is also well defined by our observations, and is seen to occur at K approximately 13.4. If the horizontal branches of M69 and 47 Tuc are assumed to have similar intrinsic brightnesses at near-infrared wavelengths, then the difference in distance moduli between the two clusters is DELTA-mu-o approximately 1.4, rather than approximately 1.7 inferred from earlier optical work. Based on this result, as well as the location of M69 stars in the (J - K,V - K) two-color and (K,V - K) color-magnitude diagrams, it is suggested that earlier V measurements of M69 stars near the level of the horizontal branch are approximately 0.3 mag too faint.