ASCA and ROSAT observations of supersoft X-ray sources

Energy spectra of four luminous supersoft X-ray sources (SSS) are investigated combining the ASCA SIS and the ROSAT PSPC data. We found that the energy spectra of the SSS are commonly reproduced by a blackbody continuum model superposed with sharp edge-like structures. Despite of several years intervals between the ASCA, and ROSAT observations, differences of the best-fit parameters are found to be small, This indicates that X-ray emissions from these foils SSS are rather stable. The blackbody temperature and the edge energies show large differences among the sources, which may reflect differences in the white dwarf mass. (C) 2000 COSPAR. Published by Elsevier Science Ltd.