  In this paper, we use different luminosity ratios to trace the histories of
star formation of two different kinds of starburst galaxies: HII galaxies and
starburst nucleus galaxies (SBNGs). The mean star formation rates (SFRs) for
these galaxies is comparable, and compatible with a near constant star
formation over a few Gyr period. We have also found an interesting difference
between the burst stellar population of the SBNGs and the HII galaxies: SBNGs
have an excess of intermediate-mass stars as compared to HII galaxies. We
interpreted this difference as a sign that SBNGs have experienced a higher
frequency of bursts of star formation than the HII galaxies. This
interpretation is qualitatively consistent with the Stochastic Self Propagation
of Star Formation (SSPSF) theory, which suggests that the starburst phenomenon
depends on internal processes, regulated by the evolution of massive stars.

Astrophysics