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

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Red giants in open clusters

VII. Melotte 71 * **

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

1 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 [FORMULA] 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

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© European Southern Observatory (ESO) 1997

Online publication: May 26, 1998

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