Gas surface density maps in the inner 5000 × 5000 au² box shown at four distinct time instances (from top to bottom row) during a close encounter with an intruder of different mass (from left to right column): 0.04 M_⊙, 0.08 M_⊙, 0.2 M_⊙, and 0.5 M_⊙. The time is counted from the launch of the intruder. The current position of the intruder is indicated with a star symbol. The dashed circles in the top row correspond to Σ_g = 0.1 g cm⁻² and thus roughly outline the outer disk extent. The scale bar is in log g cm⁻². The animation of the encounter in model C4 is available online and at http://astro.sfedu.ru/animations/encounter.mp4