Unabsorbed spectrum of PSR J0357+3205 in the optical-X-ray range. The GTC g′-band flux upper limit is indicated by the bar with an arrow. The XMM-Newton and Chandra data points are shown by grey bars⁸. The thick solid line is the best-fit BB+PL model to the X-ray data. The thin dotted line with the dark-grey filled region is the PL component with 90% uncertainties. The thick dotted line is the BB hot spot component. The thin/thick dash-dotted and dashed lines are the best-fit NSA and NSMAX components with variable/fixed normalisations. The upper limit on the thermal spectral flux from the entire surface of the NS obtained with the BB+PL+BB model is shown by the light-grey filled region. The extrapolation of the γ-ray Fermi spectrum with its uncertainties is shown by the thin solid line with a hatched region.