Observed light curve of Sw 1644+57 (open symbols), with the predicted late-time light curve (dashed lines) for a total jet energy of E_j = 10⁵² erg (Berger et al. 2012). We show the estimated 5 GHz light curve of different off-axis observers, Eq. (2), assuming that the Lorentz factor of the jet decreases with Γ_j ∝ t^-0.2, as inferred by Berger et al. (2012). We modified the extrapolated light curve to match a Sedov-Taylor solution, L_j ∝ t^-1.9, when Γ_j < 2. The 2-σ upper limits on the radio flux of seven other TDF candidates (Table 2) are shown with black triangles (we scaled these limits to the redshift of Sw 1644+57, see Sect. 4.1).