G. Carraro et F. Patat, THE STELLAR CONTENT OF THE OPEN CLUSTERS TOMBAUGH-1 AND RUPRECHT-46, Monthly Notices of the Royal Astronomical Society, 276(2), 1995, pp. 563-570
V and I CCD photometry has been carried out for two poorly known open
clusters: Tombaugh 1 and Ruprecht 46. Photometry has also been obtaine
d for nearby fields to correct for the effects of field star contamina
tion. Estimates of the cluster fundamental parameters (reddening, dist
ance and age) are given for Tombaugh 1 from comparison with theoretica
l isochrones of the Padova group. We find that this is an intermediate
-age open cluster about 1 Gyr old, and probably of solar abundance. Th
e colour excess E(B-V) and the apparent distance modulus (m-M) are abo
ut 0.40+/-0.05 and 13.60+/-0.20 mag, respectively. These results impro
ve on previous determinations of the distance, and put Tombaugh 1 at a
bout 3.0 kpc from the Sun. The high degree of contamination from field
stars prevents us from obtaining firmer results. We estimate the clus
ter radius to be about 4.0 arcmin. As for the luminosity function (LF)
, there is satisfactory agreement with that derived from the standard
Salpeter (x = 1.35) initial mass function (IMF), allowing for the unce
rtainties in the subtraction of field stars. Ruprecht 46 was poorly st
udied before. From our analysis it emerges that this object is not an
open cluster, but simply a density fluctuation above the background le
vel.