A&A Supplement series, Vol. 127, January II 1998, 167-179
Received October 11, 1995; accepted April 29, 1997
T. Richtler 
- E.K. Grebel 
- A. Subramaniam 
- R. Sagar 
Send offprint request: T. Richtler, Bonn
Sternwarte der Universität Bonn, Auf dem Hügel 71,
D-53121 Bonn, Germany
richtler@astro.uni-bonn.de
Indian Institute of Astrophysics, 560034 Bangalore, India
purni@iiap.ernet.in, sagar@iiap.ernet.in
Astronomisches Institut der Universität Würzburg, Am Hubland, D-97074
Würzburg, Germany grebel@astro.uni-wuerzburg.de
Uttar Pradesh State Observatory, Naini Tal, India
We present CCD photometry in V and I for the metal-rich globular
cluster NGC 6528. A comparison with previous photometry reveals
discrepancies of the order 0.1 to 0.2 mag in V, emphasizing the need
for independent photometry. As found previously, the giant branch
(or the asymptotic giant branch, which cannot be distinguished) of the
cluster extends to V-I = 7. Population synthesis in V-I must take these
red stars into account in order to understand integrated red colours
of bulge populations.
Currently available theoretical isochrones do not
reproduce the shape of the RGB/AGB.
The derivation of reliable values for reddening, distance
and metallicity of NGC 6528 is hampered by uncertainties in the extrapolation
to high metallicity,
which dominate the absolute error rather than
the photometric uncertainty does.
Together with other properties (old age derived from HST data, high radial
velocity), this object is more likely a member of the bulge than of the disk
population.
keywords: Galaxy: globular clusters: general; individual: NGC 6528 -- galaxy abundances -- stars: late-type -- HR diagram