Deep exposures of the metal-rich globular clusters NGC 6496 and NGC 6352 were obtained with the WFPC2 camera on board the Hubble Space Telescope ( HST ) through the F606W and F814W filters .
The resulting colour-magnitude diagrams ( CMD ) reach down to absolute magnitude M _ { 814 } \simeq 10 - 10.5 , approximately 5 magnitudes below the main sequence ( MS ) turn-off ( TO ) .
The MS of the two clusters are sharp and well defined and their fiducial lines overlap almost exactly throughout this range .
Their colour is , however , more than 0.1 mag redder than the MS fiducial line of the prototype metal-rich globular cluster 47 Tuc ( NGC 104 ) , after proper correction for the relative distances and reddening .
This provides solid empirical evidence of a higher metal content , which is not surprising if these objects belong indeed to the bulge as their present location suggests .
A good fit to the upper part of the MS of both clusters is obtained with a 10 Gyr-old theoretical isochrone from Baraffe et al .
( 1998 ) for a metallicity of [ M/H ] = -0.5 , but at lower luminosities all models depart considerably from the observations , probably because of a deficiency in the treatment of the TiO opacity .
The luminosity functions ( LF ) obtained from the observed CMD are rather similar to one another and show a peak at M _ { 814 } \simeq 9 .
The present day mass functions ( PDMF ) of both clusters are derived down to M _ { 814 } \simeq 10.5 or m \simeq 0.2 M _ { \odot } and are consistent with power-law indices \alpha = 0.7 for NGC 6496 and \alpha = 0.6 for NGC 6352 .
The PDMF of NGC 104 is twice as steep in the same mass range ( \alpha = 1.4 ) .
We investigate the origin of this discrepancy and show that it can be understood if the two clusters contain a considerably higher fraction of primordial binaries amongst their MS population , similar to that expected in the bulge .
We briefly discuss the implications of this finding on the process of star and binary formation and on the universality of the IMF .