Highest S/Ns of the weighted integrated intensity of the aligned stacked spectra achieved with a given pair of the parameters by varying the other two parameters for RY Lup. Contours from higher (dark) to lower (light) levels delineate the parameter space with achieved S/Ns of the maximum S/N − 1, − 2, and − 3. Red data points with error bars show our measurements and uncertainties reported in Table 1. The uncertainties are smaller than the parameter ranges delineated by the maximum S/N − 1 contour because of the additional constraints from the line profiles (see Sect. 3).