Astronomy and Astrophysics, volume 416, 125-136 (2004/3-2)
Proper motion surveys of the young open clusters Alpha Persei and the Pleiades.
DEACON N.R. and HAMBLY N.C.
Abstract (from CDS):
In this paper we present surveys of two open clusters using photometry and accurate astrometry from the SuperCOSMOS microdensitometer. These use plates taken by the Palomar Oschin Schmidt Telescope giving a wide field (5° from the cluster centre in both cases), accurate positions and a long time baseline for the proper motions. Distribution functions are fitted to proper motion vector point diagrams yielding formal membership probabilities. Luminosity and mass functions are then produced along with a catalogue of high probability members. Background star contamination limited the depth of the study of Alpha Per to R=18. Due to this the mass function found for this cluster could only be fitted with a power law (ξ(m)=m–α) with α=0.86+0.14–0.19. However with the better seperation of the Pleiades' cluster proper motion from the field population results were obtained down to R=21. As the mass function produced for this cluster extends to lower masses it is possible to see the gradient becoming increasingly shallow. This mass function is well fitted by a log normal distribution.
astrometry - stars: low mass, brown dwarfs - Galaxy: open clusters and associations: individual: Alpha Per, Pleiades