A&A Supplement Series, Vol. 125, October I 1997, 1-9
Received July 23, 1996; accepted September 2, 1996
V. Kravtsov
, A. Ipatov
, N. Samus,
O. Smirnov,
G. Alcaíno
, W. Liller, and F. Alvarado
Send offprint request: G. Alcaíno
Sternberg Astronomical Institute, Moscow, Russia, and
Isaac Newton Institute Moscow Branch,
13, University Ave., Moscow 119899, Russia
Institute of Astronomy of Russian Academy of Science,
Moscow, Russia, and
Isaac Newton Institute Moscow Branch, 48, Pyatnitskaya Str.,
Moscow 109017, Russia
Instituto Isaac Newton, Ministerio de Educacion de Chile,
Casilla 8-9, Correo 9,
Santiago, Chile
We have obtained new CCD photometry (with short exposures) of the Milky Way
globular cluster M 79 using the NTT under excellent seeing
. The main-sequence
turnoff point is at 
, 
; the horizontal-branch
level at the blue edge of the instability strip is 
.
The cluster metallicity, estimated from the positions of the
"bump'' on the red giant branch, is [Fe/H] 
. We discuss the
luminosity functions of the horizontal branch and the asymptotic giant
branch, in particular, the fragmentary structure of the horizontal
branch in M 79 and in other clusters.
Our isochrone analysis shows that M 79 belongs to the oldest Milky
Way globular clusters. Its age, in the scale of
Bergbusch & VandenBerg
(1992) oxygen-enhanced isochrones, is 
Gyr, and in the scale of
VandenBerg & Bell (1985) isochrones it is 
Gyr. The cluster
has an extremely blue horizontal branch at intermediate metallicity
and may be considered a good example of the "second parameter''
interpreted as age. The apparent
distance modulus of the cluster from Bergbusch and VandenBerg
isochrones is in good agreement with the value derived from the
position of the horizontal branch (
).
keywords: globular clusters: individual: M 79 -- HR diagram