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5. Cluster age

The Mv, (B-V)0 diagram for the probable members of NGC2323 has been plotted in Fig. 9 (click here). Reddening and distance corrections have been applied to the observed CM diagram, using the adopted values for the E(B-V) colour excess and apparent distance modulus. The cluster age was estimated by fitting theoretical isochrones computed by Bertelli et al. (1994), which include mass loss and moderate overshooting. Assuming a nearly solar metal content, we employed a set of isochrones corresponding to Y=0.28 and Z=0.02. Although star 121 is the only cluster member with derived metallicity (tex2html_wrap_inline1582), we believe that it may not be representative of the whole cluster.

In Fig. 9 (click here) we have drawn the ZAMS and the isochrones corresponding to log t= 7.7, 8.0, and 8.2 calculated by Bertelli et al. (1994). Both, evolutionary effects along the upper MS as well as the position of the only giant member (star 121) are satisfactorily reproduced by the isochrone corresponding to log t=8.0. So that we have adopted an age for NGC2323 of 100 Myr. This value is intermediate between those obtained by Barbaro et al. (1969) and Mostafa et al. (1983).

Figure 9: Mv vs. (B-V)0 diagram based on all stars believed to be cluster members. Isochrones corresponding to log t=7.7, 8.0 and 8.2 (Bertelli et al. 1994) are plotted

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