Proper motions in the Hyades

With epoch differences of 33 to 37 yr, we have obtained proper motions accurate to 6-12 mas/yr and have identified 393 candidate Hyads to a limiting magnitude of Mv ~ +15.5, including at least two new white dwarf candidates.

The main-sequence luminosity function determined from our sample is similar to that defined by local field stars, with a broad maximum at Mv ~ +12. Deriving distances from mu u, the proper motion towards the convergent point, and the space velocity determined by Gunn et al., we find stars with motions consistent with membership at distances of more than 15pc from the cluster centre. Moreover, both the line-of-sight and surface density distributions show evidence for significant mass segregation - indeed, the overall proper motion distribution suggests a tight core centred within a much broader distribution.