RXJ0947.0+4721 { an extremely soft Narrow Line QSO ?

RXJ0947.0+4721 is a newly discovered example of anarrow-lineSeyfert1typeobjectwithaquasarlevelluminosity (MB = 24:8). It was detected in the ROSAT All-Sky Survey (RASS) and later in 17 pointed observations of the ROSAT Po- sition sensitive Proportional Counter (PSPC). The optical spec- trum contains strong FeII emission. We apply several spectral models to the X-ray data. A single power law t yields a photon index = 4:2. Single component thermal models underesti- mate the flux above 1keV. A good t is obtained with a black- body plus power law model ( =1 :7xed) modied by Galac- tic absorption. The best t temperature is Tbb = 108 8eV, and the flux ratio in the ROSAT band is fbb=fpl = 6. Large count rate variations are visible with a maximum amplitude of a factor > 17:5. The fastest change is a drop of a factor 2.7 in 25 hours. No spectral variations were observed. The maxi- mum and minimum luminosities in the two component model are 1:010 46 ergss 1 and < 610 44 ergss 1 , respectively. We discuss possible explanations for the extreme softness and the observed variability.