Constraints on the parameters of the emitting plasma from available observations. Minimum energy requirements and the optically thin radio SED together restricts the allowed region in the plane of magnetic field (B) and radius (R). Considering the spectral break at 9.2 GHz to be due to synchrotron cooling, B can be translated to the age of the source (second y-axis). The magenta solid line and the shaded region correspond to self-absorption frequency, ν_a ≤ 400 MHz. The thick solid lines in shades of green represent B versus R relation resulting from the minimum energy argument for different values of the magnetization parameter σ (see text for details). The sensitivity on the electron energy spectral index is not high and we have used p = 1.2 in this calculation. The thin green line corresponds to the highest magnetic field possible, if 10⁵² ergs of magnetar rotational energy is converted to magnetic fields. Dashed lines in shades of blue result from equating the age obtained through synchrotron cooling with R/v, where v is assumed expansion velocity. VLBI upper limit on the radius of the source is indicated with a black arrow.