Luminosity-mass relationship from core-accretion population synthesis model at 20 Myr. Populations using different entropy assumptions are plotted, corresponding to what is traditionally referred to as cold (black) and hot start (red). The warm start (blue) model corresponds to a cold gas accretion model, but allowing for higher core masses than 17 M_Earth. Gray shaded regions correspond to the luminosity of 51 Eri b derived in this work and the mass range determined from surface gravity and radius.