VLTI/AMBER observation of SW Vir in the CO first overtone lines as well as in weak atomic and molecular lines. Panel a: observed spectrum. The identification of some of the lines is shown. Panels b–d: visibilities observed at the baselines of 9.8, 19.6, and 29.4 m, respectively. The typical errors in the visibilities are shown on the left. Panel e: observed closure phase. The typical errors are ~5°. The errorbars are not shown because they would appear too small to recognize in the plot. The ticks show the positions of the CO lines. Panels f–h: differential phases observed at the baselines of 9.8, 19.6, and 29.4 m, respectively. The typical errors at each baseline are as follows: 9.8 m: 0.5°–1° throughout the spectral window. 19.6 m: 0.5°–1° in the continuum and in the CO lines and ~3° at the CO bandhead. 29.4 m: 1°–2° in the continuum, 10°–20° in the CO lines, and ~40° at the CO band head.