We present three-dimensional numerical calculations of superbubbles evolving in a two-component interstellar medium composed of small diffuse clouds and a low-density intercloud medium. Cold H I clouds with internal densities n ˜ 10 cm-3 and radii Rcl = 3-5 pc were assumed to be embedded in a warm plane-stratified intercloud medium. The fraction of

We obtain the NaI lambdalambda8183, 8195 absorption-line radial velocity curves for the polars ST LMi and MR Ser, from which we find the semi-amplitudes to be K_abs=329+/-6 and 289+/-9 km s^-1 respectively. We find that for both systems the effects on the NaI absorption lines due to X-rays heating the inner face of the secondary are negligible, and

High and low resolution spectroscopy, together with narrow and broad band imaging have been acquired for the unusual outflow source NGC 7026. We find evidence for appreciable changes in excitation, and a highly variable emission structure, consistent in part with observed variations in electron density. The mean electron density is found to be n_e_

We have calibrated the effective temperatures of the low main sequence stars ranging spectral types from F0 to K5 versus [Fe/H] and colours (B-V), (R-I), (V-R), (V-I), (V-K), (J-H), (J-K) and ubvy-β, using a large sample of dwarfs and subdwarfs. The effective temperatures, scaled to direct T_eff_ determinations via reliable angular diameter

The 3CRR sample of radio galaxies and quasars has been cross-correlated with the ROSAT PSPC All-Sky Survey. About 25 per cent of the objects have been detected in the 0.2-2.4 keV range, the large majority being powerful radio and X-ray emitters with a range of X-ray luminosities between 10^44 and 10^46 erg s^-1. The 0.2-2.4 keV spectrum of the

We present a procedure for obtaining the cluster densities in terms of the probability, P_n_(r), for a randomly placed sphere of radius r to contain n galaxies and the cluster density profiles. We then discuss a method for computing P_n_(r) and use it to obtain the density of Abell clusters in cold dark matter models with different biasing.