A. Ruelas-Mayorga and L. J. Sánchez
Instituto de Astronomía, UNAM, Apdo. Postal 70-264, 04510 México D. F., México (rarm@astroscu.unam.mx, leonardo@astroscu.unam.mx).
Received 2005 June 3
Accepted 2005 August 15
]]> RESUMEN
Se presenta fotometría de Johnson en los filtros B y V para el cúmulo globular galáctico M92 (NGC 6341). Se obtuvieron resultados fotométricos para un total de ~ 30,000 estrellas las cuales se grafican en un diagrama V versus (B — V). Se ajustaron isócronas teóricas a este diagrama para obtener una estimación de la edad de M92. La edad que encontramos es ~ 16 x 109 años con los siguientes valores para la metalicidad y la abundancia de Helio: [Fe/H] = —2.03, Y = 0.235. El módulo de distancia al cúmulo resulta ser de m — M = 14.6 de acuerdo con el encontrado por Stetson & Harris (1988). También llevamos a cabo conteos estelares para producir una función de luminosidad, la cual se ajusta en forma exitosa con los modelos teóricos usados para el diagrama color-magnitud.
ABSTRACT
We present Johnson B and V photometry for the galactic globular cluster M92 (NGC 6341). Photometric results for a total of ~ 30,000 stars are obtained and are plotted on a V versus (B — V) diagram. We fit theoretical isochrones to this diagram in order to get an estimate for the age of M92. The age which we find is ~ 16 x 109 years with the following values for the metallicity and He-abundance: [Fe/H] = —2.03, Y = 0.235. The distance modulus to this cluster turns out to be m — M = 14.6 in accordance with that obtained by Stetson & Harris (1988). We also perform stellar counts in order to produce a luminosity function which is successfully fitted by the same theoretical models fitted to the colour-magnitude diagram.
Key Words: Galaxy: Halo — Globular clusters: Individual (NGC 6341) — Techniques: Photometric.
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