| Abstract | The CFH 3.6 m telescope has been used to find a total of 30 probable RR Lyrae variables in a field situated 40 arcmin along the minor axis from the nucleus of M31. For 28 of these objects, (Pab) = 0.548, which suggests that the variables in the halo of M31 belong to Oosterhoff's type I. The mean magnitude of the RR Lyrae variables in the M31 halo is found to be (B) = 25.68 + or - 0.06, from which a distance of 738 + or - 51 kpc is obtained. The specific frequency of these stars is found to be very similar to that of very variable-rich Galactic globular clusters. This observation suggests that the color-magnitude diagram of the halo of the Andromeda Nebula may have a very well-developed horizontal branch. The spectra of metal-rich globular clusters in M31 show strong Balmer lines, suggesting that these objects have well-developed horizontal branches. These observations suggest that the M31 halo stars and globular cluster populations have similar 'family traits' which distinguish them from Galactic Population II stars. |
