Stellar spot contamination. The top panels show the posterior distribution of the spot parameters derived from the combined data analysis. The blue shaded areas denote the 1σ highest posterior density credible region. Visits 1 and 2 show a negligible spot contamination with either a small spot covering fraction or a negligible difference between the spot and photospheric temperatures. Visit 3 in contrast shows a non-negligible contamination of ϵ(λ) ~ 1.15–1.2, with a strong correlation between the spot covering fraction and spot temperature. The bottom panel shows the respective contamination spectra. The colored symbols and vertical spans show the median and 1σ uncertainty of the contamination, respectively.