We interpret the stellar population of \omega Centauri by means of a population synthesis analysis , following the most recent observational guidelines for input metallicities , helium and [ ( C+N+O ) /Fe ] contents .
We deal at the same time with the main sequences , sub-giant and horizontal branch data .
The reproduction of the observed color magnitude features is very satisfying and bears interesting hints concerning the evolutionary history of this peculiar stellar ensemble .
Our main results are : 1 ) no significant spread in age is required to fit the colour-magnitude diagram .
Indeed we can use coeval isochrones for the synthetic populations , and we estimate that the ages fall within a \sim 0.5 Gyr time interval ; in particular the most metal rich population can be coeval ( in the above meaning ) with the others , if its stars are very helium–rich ( Y \sim 0.37 ) and with the observed CNO enhancement ( [ ( C+N+O ) /Fe ] = + 0.7 ) ; 2 ) a satisfactory fit of the whole HB is obtained , consistent with the choice of the populations providing a good reproduction of the main sequence and sub giant data .
3 ) the split in magnitude observed in the red HB is well reproduced assuming the presence of two stellar populations in the two different sequences observed : a metal poor population made of stars evolving from the blue side ( luminous branch ) and a metal richer one whose stars are in a stage closer to the zero age HB ( dimmer branch ) .
This modelization also fits satisfactorily the period and the [ Fe/H ] distribution of the RR Lyrae stars .