We present time-series photometry of two fields near M32 using archival observations from the Advanced Camera for Surveys Wide Field Channel onboard the Hubble Space Telescope .
One field is centered about 2 arcmin from M32 while the other is located 15 arcmin to the southeast of M31 .
The imaging covers a time baseline sufficient for the identification and characterization of a total number of 1139 RR Lyrae variables of which 821 are ab-type and 318 are c-type .
In the field near M32 , we find a radial gradient in the density of RR Lyraes relative to the center of M32 .
This gradient is consistent with the surface brightness profile of M32 suggesting that a significant number of the RR Lyraes in this region belong to M32 .
This provides further confirmation that M32 contains an ancient stellar population formed around the same time as the oldest population in M31 and the Milky Way .
The RR Lyrae stars in M32 exhibit a mean metal abundance of \langle [ \mathrm { Fe / H } ] \rangle \approx - 1.42 \pm 0.02 , which is \approx 15 times lower than the metal abundance of the overall M32 stellar population .
Moreover , the abundance of RR Lyrae stars normalized to the luminosity of M32 in the field analyzed further indicates that the ancient metal-poor population in M32 represents only a very minor component of this galaxy , consistent with the 1 % to 4.5 % in mass inferred from the CMD analysis of Monachesi et al .
We also find that the measured reddening of the RR Lyrae stars is consistent with M32 containing little or no dust .
In the other field , we find unprecedented evidence for two populations of RR Lyraes in M31 as shown by two distinct sequences among the ab-type variables in the Bailey Diagram .
When interpreted in terms of metal abundance , one population exhibits a peak at [ \mathrm { Fe / H } ] \approx - 1.3 and the other is at [ \mathrm { Fe / H } ] \approx - 1.9 .
One possible interpretation of this result is that the more metal-rich population represents the dominant M31 halo , while the metal-poorer group could be a disrupted dwarf satellite galaxy orbiting M31 .
If true , this represents a further indication that the formation of the M31 spheroid has been significantly influenced by the merger and accretion of dwarf galaxy satellites .