Best-fitting max and min filling factor of the star spot model for the spot temperature set to 9000 K. The orange dots mark the best-fitting model, and the orange, red, and blue contour lines mark the 68%, 90%, and 95% confidence levels. Colours indicate χ² as shown by the colour bar. Top: amplitude calculated for photometry taken at the date of UVES spectrum no. 1 and X-Shooter spectrum no. 1. Middle: amplitude calculated for the photometry taken at the date of UVES spectrum no. 1 and 2. Bottom: amplitude calculated for the photometry taken at the date of UVES spectrum no. 2 and X-Shooter spectrum no. 1. Intercomparison of the different panels lead to a spot filling factor for the date of UVES spectrum no. 1 of 18–21%, for no. 2 of 10%, and for the date of the X-Shooter spectrum no. 1 of 3–4%.