| Abstract
| - Using archival multi-epoch ACS/WFC images in the F606W and F814W filters of a resolved stellar field in Local Group dwarf elliptical galaxy M 32 we have made an accurate colour-magnitude diagram and a careful search for RR Lyr variable stars. We identified 416 bona fide RR Lyr stars over our field of view, and their spatial distribution shows a rising number density towards the centre of M 32. These new observations clearly confirm the tentative result of Fiorentino et al. (2010b, ApJ, 708, 817), on a much smaller field of view, associating an ancient population of RR Lyr variables to M 32. We associate at least 83 RR Lyr stars in our field to M 32. In addition the detection of 4 anomalous Cepheids with masses in the range 1.2−1.9 M⊙ indicates the presence of relatively young, 1−4 Gyr old, stars in this field. They are most likely associated to the presence of the blue plume in the colour-magnitude diagram. However these young stars are unlikely to be associated with M 32 because the radial distribution of the blue plume does not follow the M 32 density profile, and thus they are more likely to belong to the underlying M 31 stellar population. Finally the detection of 3 Population II Cepheids in this field gives an independent measurement of the distance modulus in good agreement with that obtained from the RR Lyr, μ0 = 24.33 ± 0.21 mag.
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