Luminosity as a function of time for planets with a mass of 1, 2, 5, and 10 M_X, as labeled in the plot. The left panel shows the case of “cold start” boundary conditions, where all accretional energy is radiated away at the shock, while the right panel shows “hot start (accreting)” models where no radiative losses occur. The dotted lines show for comparison the results of Burrows et al. (1997), while the dashed lines show Baraffe et al. (2003). Both these models use the classical “hot start” scenario. The “cold start” 1 M_X simulation is the same as shown in Fig. 3.