The dashed lines are contours of fractional mass q=φ0/φ1 for n= 1. The solid spiral is again the isothermal core solution. The top-most diagonal line is the polytrope of index 5 with α= 1. The other diagonal lines are, from top to bottom, core-envelope boundary conditions for the envelope when α= 2, 3, 4 for n= 5 as shown by Eggleton et al. (1998, Fig. 3).