  We present WFPC2-HST photometry (in the F439W and F555W bands) of the
resolved stars in NGC 1569. The derived color-magnitude diagram (CMD) contains
2800 objects down to the 26th mag, and is complete down to the 23rd. Adopting
the literature distance modulus and reddening, the CMD samples stars more
massive than 4 Mo, corresponding to a look-back time of 0.15 Gyr approximately.
The data are compared to synthetic CMDs to derive the recent star formation
history in NGC 1569. It is found that the observed field has experienced a
global burst of star formation (SF) lasting at least 0.1 Gyr, and ended a few
Myr ago. During the burst, the SF rate was approximately constant, and, if
quiescent periods occurred, they lasted less than 10 Myr. The level of the SF
rate was very high: 0.5 Mo/yr for a Salpeter IMF, in stars with mass ranging
from 0.1 to 120 Mo. When scaled for the surveyed area, the SF rate is
approximately 100 times larger than found in the most active dwarf irregulars
in the Local Group. The data are consistent with a Salpeter IMF, or slightly
steeper exponents. We discuss the implications of our results in the general
context of the evolution of dwarf galaxies.

Astrophysics