Astrophysics
We present the results of a long-term high-resolution spectroscopy campaign on the O-type stars in NGC 6231. We revise the spectral classification and multiplicity of these objects and we constrain the fundamental properties of the O-star…
The magnetohydrodynamic equations describing an inviscid, fully ionized plasma in the vicinity of a rotating black hole are derived from a two-component plasma theory within the framework of the 3+1 split of the Kerr metric. Of central…
The complete set of data from the Tenerife 10 GHz (8 degree FWHM) twin-horn, drift scan experiment is described. These data are affected by both long-term atmospheric baseline drifts and short term noise. A new maximum entropy procedure,…
Microlensing events towards the Large Magellanic Cloud entail that a sizable fraction of dark matter is in the form of MACHOs (Massive Astrophysical Compact Halo Objects), presumably located in the halo of the Galaxy. Within the present…
The theoretical prediction that trigonometric parallaxes suffer from a statistical effect, has become topical again now that the results of the Hipparcos satellite have become available. This statistical effect, the so-called Lutz-Kelker…
We report the discovery of two radio-loud quasars with redshifts greater than four; GB1428+4217 with z=4.72 and GB1713+2148 with z=4.01. This doubles the number of published radio-selected quasars with z > 4, bringing the total to 4.…
We present 14 nights of medium resolution (1-2\AA) spectroscopy of the eclipsing cataclysmic variable UU Aquarii obtained during a high accretion state in 1995 August-October. UU Aqr appears to be an SW Sextantis star, as noted by Baptista,…
It is proposed that the spectra of so called 'MeV blazars' can be explained in terms of previously developed models of the external comptonization of accretion disk radiation provided that the structure of the inner and outer parts of the…
If a galaxy resides in a cluster, then its passage through the pervasive intracluster medium will produce a detectable signature in the X-ray emission from the cluster. The simplest kinematic information that can be extracted from this…
We present deep V,I CCD photometry of the globular cluster Terzan 8, recently found to be a member of the globular cluster system of the Sagittarius dwarf spheroidal galaxy. We accurately estimate the metallicity of Ter 8 and provide the…
Using complete samples of steep-spectrum quasars, we present evidence for a correlation between radio and optical luminosity which is not caused by selection effects, nor caused by an orientation dependence (such as relativistic beaming),…
To date, the study of high-magnification gravitational lensing effects of galaxy clusters has focused upon the grossly distorted, luminous arc-like features formed in massive, centrally condensed clusters. We investigate the formation of a…
In the framework of the fluctuation-dissipation approach to dynamical friction, we derive an expression giving the orbital energy exchange experienced by a compound body as it moves interacting with a non homogeneous discrete background.…
The newly-commissioned University of New South Wales Infrared Fabry-Perot (UNSWIRF) has been used to image molecular hydrogen emission at 2.12 and 2.25 microns in the reflection nebula Parsamyan 18. P 18 is known to exhibit low values of…
We report on ROSAT HRI observations of the nearby powerful radio galaxies 3C33 and 3C111, which both have detected optical hot spots. We find nuclear X-ray sources in both objects, but no X-ray emission from the hot spots. This confirms the…
I demonstrate by means of high resolution cosmological simulations, which include modelling of a two-phase interstellar medium, that the dominant mechanism for transporting heavy elements from the proto-galaxies into the IGM is the merger…
We re-examine the Fall & Efstathiou (1980) scenario for galaxy formation, including the dark halo gravitational reaction to the formation of the baryon disk, as well as continuous variations in the intrinsic halo density profile. The…
The angular cross-correlation between two galaxy samples separated in redshift is shown to be a useful measure of weak lensing by large-scale structure. Angular correlations in faint galaxies arise due to spatial clustering of the galaxies…
We use the grid of models described in paper~I to analyse those millisecond pulsar binaries whose secondaries have been studied optically. In particular, we find cooling ages for these binary systems that range from $< 1 \rm Gyr$ to $\sim…
The presence of low mass, degenerate secondaries in millisecond pulsar binaries offers the opportunity to determine an age for the binary system independent of the rotational properties of the pulsar. To this end, we present here a detailed…