Predicted spectral energy distributions in Haro 11 illustrating the picket-fence model. The stellar spectra are obtained from two models with 20% solar metallicity – Starburst99 (Leitherer et al. 1999) (upper) and our model (Zackrisson et al. 2001) (lower). We assume that the leaking stellar population has a young age, 3 Myr, has had a constant SFR and is unaffected by extinction. The non-leaking component is assumed to be 20 Myr. In the Starburst99 model, we look at two star-formation histories of this component, an instantaneous burst and a model with continuous star-formation. In the Zackrisson et al. model, we assume an exponentially declining SFR on a timescale of 1 Gyr. The old component has been reddened by assuming the same extinction as observed in Haro 11. The Zackrisson et al. model spectra have been smoothed with a triangle smoothing to reduce the differences in spectral resolution between the stellar spectrum (low resolution) and the nebular spectrum (high resolution).