Evolved stars in open clusters.
Abstract
Radial-velocity observations and MK classifications have been used to study evolved stars in 25 open clusters. Published data on stars in 72 additional clusters are rediscussed and combined with the observations made in this investigation to yield positions in the HertzsprungRussell diagram for 559 evolved stars in 97 clusters. Ages for the parent clusters were estimated from the main-sequence turnoff points, earliest spectral types, and bluest stars in the clusters themselves. The evolved stars were sorted into six age groups ranging from 4 x I 06 yr to 4 x 1 0 yr, and the composite H-R diagram for each age group was then used to study the evolutionary tracks for stars of various masses. The observational results were found to be in reasonably good agreement with recent theoretical computations. The composite color-magnitude diagrams were found to be strikingly different from those of the rich open clusters in the Magellanic Clouds. At a given age the red giants in the Small Magellanic Cloud and the Large Magellanic Cloud clusters are brighter and bluer than their galactic counterparts. It is suggested that these effects may be accounted for by differences in metal abundance. Subject headings: clusters: open - galaxies: Magellanic Clouds - radial velocities - stars: evolution - stars: late-type - stars: spectral classification
- Publication:
-
The Astrophysical Journal Supplement Series
- Pub Date:
- April 1976
- DOI:
- 10.1086/190368
- Bibcode:
- 1976ApJS...30..451H