PHYSICAL PARAMETERS OF THE OLD OPEN CLUSTER TRUMPLER 5

Abstract

We present a study of the old open cluster Trumpler 5 (Tr 5), based on the CDS archival data. From the color-magnitude diagrams of Tr 5, we have found the positions of main-sequence turn-off (MSTO) and red giant clump (RGC) stars. Using the mean magnitude of the RGC stars, we have estimated the reddening toward Tr 5, E(B-V) = 0.60 +/- 0.10. Using the stars common in two data sets and the theoretical isochrones of Padova group, we have estimated the distance modulus V_0-M_V=12.64 +/- 0.20 (d = 3.4 +/- 0.3 kpc), the metallicity [Fe/H] = -0.30 +/- 0.10, and the age of 2.4 +/- 0.2 Gyr (log t=9.38). These metallicity and distance values are consistent with the relation between the metallicity and the Galactocentric distance of other old open clusters, for which we obtain the slope of Delta_[Fe/H]/R_gc= -0.064 +/- 0.010 dex/kpc.