Bibcode
DOI
Caputo, F.; Chieffi, A.; Castellani, V.; Collados, M.; Martinez Roger, C.; Paez, E.
Bibliographical reference
Astronomical Journal (ISSN 0004-6256), vol. 99, Jan. 1990, p. 261-272.
Advertised on:
1
1990
Citations
34
Refereed citations
33
Description
CCD photometry for stars in three fields centered on the old open
cluster NGC 188 is presented, with the aim of investigating the HR
diagram distribution of cluster main-sequence stars. A sequence of
subgiant, turnoff, and main-sequence stars has been detected, extending
the observed lower main sequence down to about m(v) = 20 mag. It is
found that the observed color-magnitude diagram appears well fitted by a
theoretical isochrone for an age of about 6-billion yr, provided that
Yale transformations from the theoretical into the observational plane
are assumed. From the distribution of the stellar luminosities, it is
found that the turnoff stars should have masses of about 1.3 solar mass.
The cluster evolutionary scenario is discussed in connection with the
reported luminosity of the clump of He-burning giants.