A high resolution spectroscopic observation of CAL 83 with XMM-Newton/RGS

We present the first high resolution photospheric X-ray spectrum of a Super soft X-ray Source, the famous CAL 83 in the Large Magellanic Cloud. The spe ctrum was obtained with the Reflection Grating Spectrometer on XMM-Newton d uring the Calibration/Performance Verification phase of the observatory. Th e spectrum covers the range 20-40 Angstrom at an approximately constant res olution of 0.05 Angstrom, and shows very significant, intricate detail, tha t is very sensitive to the physical properties of the object. We present th e results of an initial investigation of the spectrum, from which we draw t he conclusion that the spectral structure is probably dominated by numerous absorption features due to transitions in the L-shells of the mid-Z elemen ts and the hf-shell of Fe: in addition to a few strong K-shell features due to CNO.