Astron. Astrophys. Suppl. Ser. 134, 301-308

Membership, binarity and metallicity of red giants in the southern open cluster NGC2354

J.J. Clariá¹ - J.-C. Mermilliod² - A.E. Piatti¹

Send offprint request: J.J. Clariá,
e-mail: claria@oac.uncor.edu

1 - Observatorio Astronómico, Laprida 854, 5000 Córdoba, Argentina
2 - Institut d'Astronomie de Lausanne, CH-1290, Chavannes-des-Bois, Switzerland

Received June 17; accepted August 12, 1998

Abstract:

We present new Coravel radial-velocity observations and photoelectric photometry in the UBV, DDO and Washington systems for a sample of red giant candidates in the field of the intermediate-age open cluster NGC2354. Photometric membership probabilities show very good agreement with those obtained from Coravel radial velocities. The analysis of the photometric and kinematical data allow us to confirm cluster membership for 9 red giants, one of them being a spectroscopic binary, while 4 confirmed spectroscopic binaries appear to be probable members. We have also discovered 4 spectroscopic binaries not belonging to the cluster. A mean radial velocity of (33.40 $\pm$ 0.27) km s^-1 and a mean reddening E(B-V) = 0.13 $\pm$ 0.03 were derived for the cluster giants. NGC 2354 has a mean ultraviolet excess $<\delta(U-B)\gt$= -0.03 $\pm$ 0.01, relative to the field K giants, and a mean new cyanogen anomaly $\Delta CN = -0.035$ $\pm$ 0.007, both implying [Fe/H] $\approx$ -0.3. The moderately metal-poor character of NGC2354 is confirmed using five different metal abundance indicators of the Washington system. The cluster giant branch is formed by a well defined clump of 7 stars and 4 stars with high membership probabilities seem to define an ascending giant branch. The whole red giant locus cannot be reproduced by any theoretical track.

Key words: open clusters: individual: NGC2354 -- stars: HR diagram; abundances