An XMM-Newton observation of the nova-like variable UX UMa: spatially   and spectrally resolved two-component X-ray emission
  In the optical and ultraviolet regions of the electromagnetic spectrum, UX Ursae Majoris is a deeply eclipsing cataclysmic variable. However, no soft X-ray eclipse was detected in ROSAT observations. We have obtained a 38 ksec XMM-Newton observation to further constrain the origin of the X-rays. The combination of spectral and timing information allows us to identify two components in the X-ray emission of the system. The soft component, dominant below photon energies of 2 keV, can be fitted with a multi-temperature plasma model and is uneclipsed. The hard component, dominant above 3 keV, can be fitted with a kT ~ 5 keV plasma model and appears to be deeply eclipsed. We suggest that the most likely source of the hard X-ray emission in UX UMa, and other systems in high mass transfer states, is the boundary layer. 
G.W. Pratt (1 and 2), K. Mukai (3), B.J.M. Hassall (4), T. Naylor (5),   J.H. Wood (6) ((1) CEA/Saclay Service d'Astrophysiq...