Line-profiles predicted for models with a gap in the intensity distribution: a) line-profiles expected for a intensity distribution with a gap devoid of gas from 2.5 AU to 6 AU, in orange the contribution from 1.2 to 2.5 AU, in blue the contribution from 6 to 15 AU, and in red the total line-profile; b) similar plot but for a gap devoid of gas of width 1 AU extending from 5 to 6 AU. Error bars on the spectrum are 1σ.