The complex X-ray spectrum of the supersoft source

We present the X-ray spectrum of / , obtained with the Medium Energy Grating spectrometer of the Chandra X-ray Telescope. The simplest models used by earlier authors, stellar atmospheres in combination with a thermal plasma in collisional ionization equilibrium, cannot explain the spectrum. Neither does a photo-ionized plasma. We identify P Cygni profiles of Fe XVII and O VIII, from which we conclude that these lines arise in a wind. We conclude that major uncertainty exists about the bolometric luminosity of , and perhaps of supersoft sources in general, so that the theoretical prediction that this luminosity derives from steady nuclear burning cannot be verified.