ROSAT AND EUVE OBSERVATIONS OF THE NOVA-LIKE VARIABLE IX-VELORUM

We have obtained ROSAT PSPG and EWE DSS observations of the nova-like variable IX Vel. The ROSAT data show irregular variations on time scal es ranging from 50s to a month. The x-ray flux varies with an amplitud e of 15-20 % on the orbital period, mainly due to variation in emissio n measure, and reaching minimum when the white dwarfis closest to Eart h. The EUV and x-ray flux can be modelled with a single optically thin spectrum. Its bolometric flux is much less than the optical and ultra violet flux of the accretion disk. Orbital and long-term variations ar e also found in the EWE data, and have a larger amplitude than the x-r ay variations. This can be explained with variations in absorption col umn on these time scales. In the xray data there is significant spectr al variability, in part due to a variable absorption column, which yie lds a complex relation between the x-ray count rate and hardness ratio . The origin of the x-rays in IX Vel is discussed and we are forced to conclude that there is as yet no satisfactory explanation for the obs erved orbital modulation in the x-ray flux.