Washington photometry of five star clusters in the Large Magellanic Cloud

Aims: We present CCD photometry in the Washington system C and T₁ passbands down to T₁ ~ 22.5 in the fields of NGC 1697, SL 133, NGC 1997, SL 663, and OHSC 28, five mostly unstudied star clusters in the LMC.
Methods: Cluster radii were estimated from star counts in appropriate-sized boxes distributed throughout the entire observed fields. We perform a detailed analysis of the field star contamination and derive cluster colour-magnitude diagrams (CMDs). Based on the best fits of isochrones computed by the Padova group to the (T_1, C-T_1) CMDs, the δ(T_1) index and the Standard Giant Branch procedure, we derive metallicities and ages for the five clusters. We combine our sample with clusters with ages and metallicities on a similar scale and examine relationships between position in the LMC, age and metallicity.
Results: With the exception of NGC 1697 (age = 0.7 Gyr, [Fe/H] = 0.0 dex), the remaining four clusters are of intermediate-age (from 2.2 to 3.0 Gyr) and relatively metal-poor ([Fe/H] = -0.7 dex). The cluster and field age-metallicty realtions show evidence for a metallicity offset but do overlap, particularly on the upper envelope side of the cluster age-metallicity relation.
Conclusions: We confirm previous results that clusters younger than ~1 Gyr were formed during an outside-in process; this occurred after a burst of cluster formation that took place mainly in the outer disk and peaked at ~2 Gyr ago.

Tables 2-6 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/501/585