The star formation history of the Large Magellanic Cloud star clusters
  NGC1846 and NGC1783
  NGC1846 and NGC1783 are two massive star clusters in the Large Magellanic
Cloud, hosting both an extended main sequence turn-off and a dual clump of red
giants. They present similar masses but differ mainly in angular size. Starting
from their high-quality ACS data in the F435W, F555W and F814W filters, and
updated sets of stellar evolutionary tracks, we derive their star formation
rates as a function of age, SFR(t), by means of the classical method of CMD
reconstruction which is usually applied to nearby galaxies. The method confirms
the extended periods of star formation derived from previous analysis of the
same data. When the analysis is performed for a finer resolution in age, we
find clear evidence for a 50-Myr long hiatus between the oldest peak in the
SFR(t), and a second prolonged period of star formation, in both clusters. For
the more compact cluster NGC1846, there seems to be no significant difference
between the SFR(t) in the cluster centre and in an annulus with radii between
20 and 60 arcsec (from 4.8 to 15.4 pc). The same does not occur in the more
extended NGC1783 cluster, where the outer ring (between 33 and 107 arcsec, from
8.0 to 25.9 pc) is found to be slightly younger than the centre. We also
explore the best-fitting slope of the present-day mass function and binary
fraction for the different cluster regions, finding hints of a varying mass
function between centre and outer ring in NGC1783. These findings are discussed
within the present scenarios for the formation of clusters with multiple
turn-offs.
