Effect of the luminosity bursts on the spatial distribution of gas-phase CO and CO₂. The four columns present (from left to right) the gas surface density distribution (log g cm^-2), gas temperature (K), CO gas-phase fraction, and CO₂ gas-phase fraction in the inner 3000 × 3000 AU region. The four rows show (from top to bottom) the pre-burst phase (t = 0.128 Myr), the burst phase (t = 0.13 Myr), the post-burst phase (t = 0.134 Myr) and the quiescent phase (t = 0.14 Myr). The black lines are isotemperature contours outlining the regions where gas temperature exceeds 20 K (third column) and 40 K (fourth column) above which CO and CO₂ are supposed to be in the gas phase in an equilibrium, time-independent case.