Illustration of the analysis approach based on Gaussian model fitting using the example of interferometric observations obtained with AMBER in 20 February 2009, 1 May 2009, and 27 June 2009 for V856 Sco (see Appendix B for details). We plot to compare the Gaussian best-fit models M_2009-02-20 (black diamonds), M_2009-05-01 (blue dots), and M_2009-06-27 (red squares) to the interferometric data (visibilities and phases; D_2009-02-20, D_2009-05-01, and D_2009-06-27) from the different epochs. The upper and lower -limits indicating temporal variability when comparing data with best-fit models of the same and different epochs are plotted as gray solid lines.