The old anticentre open cluster Berkeley 32: membership and fundamental parameters

We have obtained medium- and low-resolution spectroscopy and BVI CCD imaging of Berkeley 32, an old open cluster which lies in the anticentre direction. From the radial velocities of 48 stars in the cluster direction, we found that 31 of them, in crucial evolutionary phases, are probable cluster members, with an average radial velocity of +106.7 (sigma= 8.5) km s(-1). From isochrone fitting to the colour-magnitude diagrams of Berkeley 32, we have obtained an age of 6.3 Gyr, (m-M)(0)= 12.48 and E(B-V) = 0.10. The best fit is obtained with Z= 0.008. A consistent distance, (m-M)(0)similar or equal to 12.6 +/- 0.1, has been derived from the mean magnitude of red clump stars with confirmed membership; we may assume (m-M)(0)similar or equal to 12.55 +/- 0.1. The colour-magnitude diagram of the nearby field observed to check for field stars contamination looks intriguingly similar to that of the Canis Major overdensity.