The Main-Sequence Color-Magnitude Diagram of M92
Abstract
A new color-magnitude (C-M) diagram for main-sequence stars in the globular cluster M 92 is presented. The observations upon which this diagram is based were obtained with an RCA CCD at the 3.6 m Canada-France-Hawaii telescope. These new data refine the position of the cluster ridge lines in the lower main sequence, the subgiant branch, and the lower giant branch. A comparison of the new C-M diagram with new theoretical isochrones shows that the shapes of the models are in good agreement with the observations, but a large shift in color is required to bring the theory and observations into agreement. Possible explanations for this discrepancy are discussed. The new M 92 observations and recent work on M13, M15, and 47 Tuc combined with the new isochromes show that the globular cluster distance scale developed by Sandage from the RR Lyrae period-luminosity-amplitude relation is consistent for the relative distances if all the clusters are the same age.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 1986
- DOI:
- 10.1086/164459
- Bibcode:
- 1986ApJ...307..738H
- Keywords:
-
- Color-Magnitude Diagram;
- Globular Clusters;
- Main Sequence Stars;
- Stellar Evolution;
- Charge Coupled Devices;
- Chronology;
- Stellar Models;
- Stellar Spectrophotometry;
- Astrophysics;
- CLUSTERS: GLOBULAR;
- STARS: EVOLUTION