Bibcode
DOI
Delgado, A. J.; Alfaro, E. J.; Aparicio, A.; Cabrera-Cano, J.
Bibliographical reference
Astronomical Journal (ISSN 0004-6256), vol. 108, no. 6, p. 2193-2202
Advertised on:
12
1994
Citations
4
Refereed citations
3
Description
The results of a UBVR photometric study in the field of the open cluster
IC 1311 are presented. A comparison with previously published results on
NGC 7044, based on measurements secured during the same observing run,
leads to a self-consistent constraints to the parameters of the cluster.
The location of selected samples of giant and unevolved dwarf members in
the U-B vs B-V diagram is used to simultaneously compute the color
excess E(B-V) and the metallicity (Fe/H). Distance modulus and age are
estimated by the Zero Age Main Sequence (ZAMS) fitting method, and by
the use of theoretical isochrones, based on models computed with and
without the consideration of convective overshooting during the phases
of core nuclear burning. The adopted set of values is: E(B-V) = 0.28,
(Fe/H) = 0.0, DM = 13.9, Age = 1.6 x 109 yr. The mass
function for the cluster main sequence has been estimated, with a slope
x = -2.58, significantly steeper than the Salpeter initial mass function
(IMF) (-1.35). The uncertainties in the adopted values for the cluster
parameters, due to interstellar reddening, and to the calibrations of
theoretical luminosity and effective temperature in terms of
observational quantities, are also addressed. The discrepancies between
the observational color-magnitude (CM) and the model isochrones, in
particular the difference between observed and predicted luminosity of
the red giant clump (RGC), are sensibly reduced for the models with
convective core overshooting. The results indeed suggest the need of
increasing the overshooting effectiveness beyond the values considered
up to now in evolutionary computations.