Rolloff energy Erolloff (determined in Section 3.3) of regions around the rim of Tycho vs. expansion parameter m (as listed in Table 2 of Reynoso et al. 1997). Overplotted are three curves that represent different dependences of Erolloff on m: Erolloff ∝ m2 (cyan solid line), Erolloff ∝ m4 (red dashed line), and Erolloff ∝ m7 (blue dotted line). These dependences are derived using the expressions in Equations (6)–(8) and given that R ∝ tm, so vs = mR/t ∝ m. The former two trends are those expected if the maximum energy of the electrons is limited by the age of the SNR or by the timescale of the radiative losses, respectively. The latter curve represents the loss-limited case if the B-field strength is not constant (and instead B ∝ vs ∝ m). The Erolloff ∝ m2 trend does not match the data for large m, and thus, the age-limited scenario is more consistent with our results.