Left panel: placement of HIP 65426 b (point with error bars) in the age-luminosity diagram. The dots show other direct detections from the literature; the error bars are omitted for clarity. No formation delays Δt_form are subtracted. The cooling curves are the BEX hottest starts (Eq. 1a) with the AMES-COND (Baraffe et al. 2003) atmospheres for masses of m_p = 1–40 M_J (bottom to top; see labels and legend). Right panel: effect of different post-formation luminosities, as given by the populations of Mordasini et al. (2017): hottest starts (as in the left panel), cold-nominal population, cold-classical population, and coldest starts (thick to thin lines; see Eq. (1)). Only masses of m_p = 6 (black), 8 (blue), 10 (orange), and 12 M_J (red) are shown (bottom to top). The axis ranges relative to the left panel are different.