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Deep exposures of the metal-rich globular clusters NGC6496 and NGC6352 wereobtained with the WFPC2 camera on board the HST through the F606W and F814Wfilters. The resulting colour-magnitude diagrams reach down to absolutemagnitude M_814~10-10.5, approximately 5 magnitudes below the main sequence(MS) turn-off. The MS of the two clusters are sharp and well defined and theirfiducial lines overlap almost exactly throughout this range. Their colour is,however, more than 0.1 mag redder than the MS fiducial line of the prototypemetal-rich globular cluster 47 Tuc, after proper correction for the relativedistances and reddening. This provides solid empirical evidence of a highermetal content, which is not surprising if these objects belong indeed to thebulge as their present location suggests. A good fit to the upper part of theMS of both clusters is obtained with a 10 Gyr-old theoretical isochrone fromBaraffe et al. (1998) for a metallicity of [M/H]=-0.5, but at lower luminosityall models depart considerably from the observations, probably because of adeficiency in the treatment of the TiO opacity. The luminosity functionsobtained from the observed CMD are rather similar to one another and show apeak at M_814~9. The present day mass functions (PDMF) are derived down tom~0.2 Msolar and are consistent with power-law indices alpha=0.7 for NGC6496and alpha=0.6 for NGC6352. The PDMF of 47 Tuc is twice as steep in the samemass range (alpha=1.4). We investigate the origin of this discrepancy and showthat it can be understood if the two clusters contain a considerably higherfraction of primordial binaries amongst their MS population, similar to thatexpected in the bulge. We briefly discuss the implications of this finding onthe process of star and binary formation and on the universality of the IMF.Comment: Accepted for publication in Astronomy and Astrophysics. Prepared with  aatex, 12 pages, 7 figure

HST observations of the metal rich globular clusters NGC 6496 and NGC 6352