Dipole (ℓ = 1) average of the computed period spacings, , assessed in a range of periods that includes the periods observed in RX J2117, shown as solid (dashed) curves corresponding to stages before (after) the maximum T_eff for different stellar masses. The location of RX J2117 when we use the effective temperature derived by Rauch & Werner (1997), T_eff = 170 000  ±  10 000 K, and the period spacing Δ Π = 21.669  ±  0.030 s derived in Sect. 4.1 is highlighted with a red circle. We include the error bars associated with the uncertainties in and T_eff. The stellar mass derived by interpolation is M_⋆ = 0.569  ±  0.015 M_⊙.