Response of the spiral pattern to bursts of different duration. The gas surface density in the inner 400 × 400 au² box is shown. Columns from left to right represent models with different burst durations: 500 yr, 200 yr, 100 yr, and the model without the burst. The initial 500 yr since the onset of the burst with a constant-magnitude shape are shown. The red line separates disk images in the burst phase from those in the post-burst or no-burst phase. The scale bar is in log g cm⁻².