Contour plots of the solutions found for 1RXS J101015.9 - 311909. The contours are expressed in arbitrary units representing the number of solutions corresponding to a given pair of parameters. White represents zero. As discussed in Sect. 2, the most extended contour corresponds to a 1-σ contour with respect to the best-fit solution, as determined a posteriori. Top left: contours in the B–δ plane. The shadowed regions represent the exclusion regions defined following T98 (the region filled with diagonal lines is computed from Eq. (4), while the region filled with dots is computed from Eq. (11), considering an emitting region size equal to (1 + z)cτ_var/δ and (1 + z)cτ_var/30δ). We do not include the constraint on the consistency of γ_break with synchrotron cooling). Top right: contours in the R–δ plane. The filled region corresponds to a variability time-scale higher than 24 h. Bottom left: contours in the γ_break–B²R plane. The black lines represent the expected value of γ_break in the presence of pure synchrotron cooling, assuming a value of β_esc equal to (from left to right) 1/100, 1/50, and 1/6. Bottom right: contours in the u_e–u_B plane. The black lines correspond to u_e/u_B values equal to (from bottom to top) 10, 50, and 100, respectively.