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  • Print publication year: 2000
  • Online publication date: August 2010

The Mass Function of the Pleiades

from I - Searches in Clusters, Stellar Associations and the Field
    • By R. F. Jameson, Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK, S. T. Hodgkin, Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1, 7RH, UK, D. Pinfield, Department of Pure and Applied Physics, The Queen's University of Belfast, Belfast, BT7 1NN, Northern Ireland, M. R. Cossburn, Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK
  • Edited by Rafael Rebolo, Instituto de Astrofísica de Canarias, Tenerife, Maria Rosa Zapatero-Osorio, Instituto de Astrofísica de Canarias, Tenerife
  • Publisher: Cambridge University Press
  • DOI: https://doi.org/10.1017/CBO9780511564758.007
  • pp 59-67

Summary

We combine the results from two CCD surveys covering a large area of the custer at I and Z wavebands. We have obtained follow-up K photometry for many of the numerous brown dwarf candidates discovered in these surveys which we employ as a test for cluster membership. From these data we derive the mass function of the whole Pleiades cluster down to 0.04 M. We emphasise the importance of a careful consideration of the spatial distribution within the cluster and find the core radius for brown dwarfs to be 2±1 parsecs. The contribution of brown dwarfs to the total mass of the cluster is about 1%.

Introduction

The Pleiades has long been recognised as one of the best places to search for brown dwarfs, e.g. Jameson & Skillen (1989), Stauffer et al. (1989, 1994), Simons & Becklin (1992), Rebolo et al. (1995), Cossburn et al. (1997), Zapatero Osorio et al. (1997), Bouvier et al. (1998), Festin (1998).

The cluster is both reasonably close (but not so close as to cover too large an area of the sky) and young, so that brown dwarfs are not too faint. Controversy still rages over the precise distance to the Pleiades, which Hipparcos places significantly closer (at 118 parsecs) than ground based measurements (at typically 133 parsecs). The Hipparcos results have been published by Van Leeuwen & Hansen Ruiz (1997) and Mermilliod et al. (1997) and critically discussed by Pinnsoneault et al. (1998).