Age of M92 and M15
Comparison of VandenBerg's isochrones for globular clusters with the photometry of many main-sequence stars in M92 and M15 gives an age of T = 18 +- 2 x 10/sup 9/ years for both clusters, using a vertical fit to the turn-off luminosity, together with distance modulii found from the period-color-luminosity relation of their RR Lyrae stars. Comparison of the systematics of the composite CM diagram for clusters of different metallicity with that predicted from VandenBerg's isochrones, all for T = 18 x 10/sup 9/ years, shows good agreement. Justification of the adopted zero-point value of M/sub v/ (RR,M92) = +0.63 is made by comparing the main sequences of M92, M3, and M5 with that defined by 11 field subdwarfs whose metallicities lie between (Fe/H) of -2.2 and -1.2 for which adequate astrometric distances exist.
- Research Organization:
- Mount Wilson and Las Campanas Observatories, Carnegie Institution of Washington, Pasadena, California 91101
- OSTI ID:
- 5839596
- Journal Information:
- Astron. J.; (United States), Journal Name: Astron. J.; (United States) Vol. 88:8; ISSN ANJOA
- Country of Publication:
- United States
- Language:
- English
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