NEW INTERMEDIATE POLARS DISCOVERED IN THE ROSAT SURVEY - 2 SPECTRALLYDISTINCT CLASSES

We report the discovery of new intermediate the galactic plane, detect ed during the ROSAT all-sky survey. Three new systems (RX J0028.8+5917 , RX J0153.3+7446 and RX J1712.6-2414) are characterized by hard ROSAT spectra, consistent with intrinsically absorbed thermal bremsstrahlun g as was seen from intermediate polars known before ROSAT. Another int ermediate polar candidate (RX J1914.4+2456) shows together with RX J05 58.0+5353 and RE 0751+14 a soft blackbody-like spectrum similar to the soft X-ray spectra of polars. The blackbody temperatures kT for this new class of soft intermediate polars are in the range of about 40 - 6 0 eV, somewhat higher than typically found for polars. The similaritie s to polars at the lower end of their magnetic field strength distribu tion, together with the longer orbital period of RX J0558.0+5353 and R E 0751+14, strongly suggest the class of soft intermediate polars as e volutionary progenitors of polars which have not synchronized the orbi tal and white dwarf rotation yet.