X-ray spectrum of I Zw 18. The X-ray emission is calculated with a diskbb model (distribution of blackbodies from an accretion disk). The diamonds show the unfolded XMM-Newton spectrum. The dashed red line shows the spectrum absorbed by I Zw 18 alone while the dotted red line shows the spectrum absorbed by the Milky Way alone. The top red solid line shows the intrinsic (unabsorbed) X-ray spectrum. The thick black curve shows the sum of the radiation field components (two blackbodies in the optical and the X-ray source).