ASCA OBSERVATIONS OF SS CYGNI DURING AN ANOMALOUS OUTBURST

SS Cygni was observed by the ASCA satellite on 1993 May 27, the first catalysmic variable studied by ASCA. The observations were conducted w hile the system was in an outburst of the ''anomalous'' variety. The S IS spectrum cannot be explained by two-temperature Raymond-Smith coron al plasma models as invoked in previous studies with lower spectral re solution. Significantly better agreement is found for models with plas ma emission at kT = 0.8, 3.5 keV and thermal bremsstrahlung at kT = 18 keV. The GIS data are consistent with the SIS data, showing evidence for Fe line emission but showing no evidence of pulsation over times r anging from seconds to minutes. These observations seem at variance wi th standard theory in two regards: we simultaneously see hard X-rays a nd optically thin soft X-rays while the system is in outburst, and we see a nonsmooth emission measure distribution. We speculate on possibl e scenarios which might resolve these differences.