Astron. Astrophys. 324, 91-96 (1997)

Red giants in open clusters

VII. Melotte 71 ^{* **}

J.-C. Mermilliod ¹, J.J. Clariá ², J. Andersen ³ and M. Mayor <sup>4

1</sup> Institut d'Astronomie de l'Université de Lausanne, CH-1290 Chavannes-des-Bois, Switzerland
² Observatorio Astronómico, Laprida 854, 5000 Córdoba, Argentina
³ Niels Bohr Institute for Astronomy, Physics, and Geophysics, Astronomical Observatory, Juliane Maries Vej 30, DK-2100 Copenhagen O, Denmark
⁴ Observatoire de Genève, CH-1290 Sauverny, Switzerland

Received 7 November 1996 / Accepted 6 December 1996

Abstract

New CORAVEL radial-velocity observations and UBV photometry of 24 red giants in the field of the intermediate-age open cluster Mel 71 are analysed for membership and duplicity. The membership of 16 stars is confirmed, one star is a possible member, and 8 spectroscopic binaries have been discovered, all amongst the cluster stars. Four of their orbits have been determined, with periods ranging from 74 to 1627 days. The mean cluster velocity is +50.14 0.14 (s.e.) km s^-1, and the binary frequency is unusually high (8/16 = 50%). The best isochrone fit to the observed colour-magnitude digram is obtained for logt = 9.00 and Z = 0.008. However, some discrepancies appear between the observed and predicted locations of the red giant clump.

Key words: cluster: open individual: Mel 71 binaries: spectroscopic HR diagram

* Based on observations collected with the Danish 1.54-m telescope at the European Southern Observatory, La Silla, Chile and at Cerro Tololo Interamerican Observatory
** Table 4 is available in electronic form at the CDS by ftp at 130.79.128.5

Send offprint requests to: J.-C. Mermilliod

SIMBAD Objects

Contents

• 1. Introduction
• 2. Observations
  • 2.1. Radial-velocity measurements
  • 2.2. Photometry
  • 2.3. Results
• 3. Discussion
  • 3.1. Mean cluster velocity
  • 3.2. Membership
  • 3.3. Spectroscopic binaries
  • 3.4. The colour-magnitude diagram
• 4. Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: May 26, 1998

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