SIMBAD references

A cataclysmic variable is a binary system consisting of a white dwarf that accretes material from a secondary object via the Roche-lobe mechanism. In the case of long enough observation, a detailed temporal analysis can be performed, allowing the physical properties of the binary system to be determined. We present an XMM-Newton observation of the dwarf nova HT Cas acquired to resolve the binary system eclipses and constrain the origin of the X-rays observed. We also compare our results with previous ROSAT and ASCA data. After the spectral analysis of the three EPIC camera signals, the observed X-ray light curve was studied with well known techniques and the eclipse contact points obtained. The X-ray spectrum can be described by thermal bremsstrahlung of temperature kT₁=6.89±0.23keV plus a black-body component (upper limit) with temperature kT₂=30_–6⁺⁸eV. Neglecting the black-body, the bolometric absorption corrected flux is F^Bol=(6.5±0.1)x10^–12 erg s^–1/cm2, which, for a distance of HT Cas of 131 pc, corresponds to a bolometric luminosity of (1.33±0.02)x10³¹ erg/s. In a standard accretion scenario where L_BL≃0.125L_acc assuming Ω_WD≃0.5Ω_K(R_WD), the amount of matter accreting onto the central white dwarf is found to be 1.7x10 ^–11M_☉/yr. The study of the eclipse in the EPIC light curve permits us to constrain the size and location of the X-ray emitting region, which turns out to be close to the white dwarf radius. We measure an X-ray eclipse somewhat smaller (but only at a level of ≃1.5 σ) than the corresponding optical one. If this is the case, we have possibly identified the signature of either high latitude emission or a layer of X-ray emitting material partially obscured by an accretion disk.