We present new results on the star formation history of the dwarf irregular galaxy NGC 1569 .
The data were obtained with Hubble Space Telescope ’ s NICMOS/NIC2 in the F110W ( J ) and F160W ( H ) near-infrared ( NIR ) filters and interpreted with the synthetic color-magnitude diagram method .
The galaxy experienced a complex star formation ( SF ) activity .
The best fit to the data is found assuming three episodes of activity in the last 1 - 2 Gyr .
The most recent and strong episode constrained by these NIR data started \sim 3.7 \times 10 ^ { 7 } yr ago and ended \sim 1.3 \times 10 ^ { 7 } yr ago , although we can not exclude that up to three SF episodes occurred in this time interval .
The average star-formation rate ( SFR ) of the episode is \sim 3.2 M _ { \odot } yr ^ { -1 } kpc ^ { -2 } , in agreement with literature data .
A previous episode produced stars between \sim 1.5 \times 10 ^ { 8 } yr and \sim 4 \times 10 ^ { 7 } yr ago , with a mean SFR about 2/3 lower than the mean SFR of the youngest episode .
An older SF episode occurred about 1 \times 10 ^ { 9 } yr ago .
All these SFRs are 2 - 3 orders of magnitude higher than those derived for late-type dwarfs of the Local Group .
In all cases an initial mass function similar to Salpeter ’ s allows for a good reproduction of the data , but we can not exclude flatter mass functions .
These results have been obtained adopting a distance of 2.2 Mpc and a reddening E ( B-V ) =0.56 .
A larger distance would require younger episodes and higher SFRs .
We have explored some possible scenarios using the astrated mass in the best fit model , in order to constrain the past star formation history .
We can not rule out a low rate in the past SF but we can safely conclude that the last 1 - 2 Gyr have been peculiar .