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Astron. Astrophys. 320, 74-78 (1997)

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1. Introduction

In an effort to enlarge the sample of Pleiades members in the outer part of the cluster, we have observed a new sample of stars selected from the proper motion study by Artjukhina & Kalinina (1970, hereafter referred to as AK). In the first paper of this series (Rosvick et al. 1992a, paper I), we have observed 83 stars in the corona of the Pleiades selected on the basis of the proper motions and Walraven photometry published by van Leeuwen et al. (1986). Our radial velocities, obtained with the CORAVEL scanner (Baranne et al. 1979), enabled us to confirm the cluster membership of 56 F5-K0 main-sequence stars. We realised that we had not included the stars proposed by AK, of which the list extracted from van Leeuwen's paper was only a sub-sample. The reason is that AK published only (x,y) position which makes the identification of the stars on the sky more difficult. Stauffer et al. (1991) published new proper motions for faint stars in the Pleiades and gave coordinates for many AK stars. This enabled us to compute an initial set of coordinates for all AK stars and then to match the AK stars up with HST GSC stars. We used the GSC facilities developed at the Geneva observatory to get for each star a detailed map and better coordinates.

The evidences for the existence of a corona around open clusters have been developed in the introductory section of paper I, as well as the importance to identify the stars individually and not statistically. In the present paper we consider the area covered by Hertzsprung's (1947) study as the inner part of the Pleiades (out to [FORMULA] of the cluster center) and everything outside this zone as the outer part. This subdivision will be refined in the next paper of this series which will be devoted to the study of the structure of the Pleiades (Raboud et al. 1996).

This paper discusses the new radial-velocity observations made for the present sample and the CCD observations in the Geneva photometric system which were obtained for candidate members. We thus have all data at hand to examine the membership of these stars to the Pleiades.

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© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998
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