1999A&A...342..839B

We reconsider two ROSAT observations of the Vela SNR shock region, with the aim to overcome the problems encountered in interpreting the X-ray spectra in terms of single-temperature NEI emission model. We pursue the idea of the association of the observed cool and hot components with an high-density (``inhomogeneities") and a low-density (``intercloud") ISM phase, respectively. We derive the density (0.5-1.0cm^–3) and the volume filling factor (0.2-0.8) of the inhomogeneities on a scale length of 10' (∼1pc), and we identify two regions of the main shock interactions, one with a small (∼1pc) isolated cloud, and the other with a larger feature (∼4-5pc, perhaps a cavity wall). We argue that the thermal evaporation from shocked clouds may account for the mass of observed inhomogeneities. After isolating the emission of the dynamically unperturbed intercloud medium, we apply the Sedov analysis and estimate the explosion energy of the supernova event (E₀∼1.2x10⁵⁰erg) and the distance (∼280pc, in agreement with recent results). Our data also indicate fast electron-ion equipartition behind the shock. The influence of Non-Equilibrium of Ionization effects on our conclusions are estimated.