The observations and simulations have revealed that large-scale magnetic field and outflows can exist in the inner regions of an advection-dominated accretion disc where the resistive diffusion may also be important. In the present paper, the roles of large-scale magnetic field and outflows in the structure of resistive advection-dominated accretion discs are explored by assuming that the accretion flow is radially self-similar. In the non-ideal magnetohydrodynamic (MHD) approximation, the results show that the angular velocity is always sub-Keplerian when both the outflow and the large-scale magnetic field are taken into account. A stronger toroidal field component leads to faster rotation, while the disc rotates with faster rate if the vertical field component is weaker. The increase of magnetic diffusivity causes the infall velocity to be close to Keplerian velocity. Although the previous studies in the ideal MHD approximation have shown that the disc temperature decreases due to the vertical field component, we find that the effect of vertical field component on the temperature of a resistive disc depends on the magnetic diffusivity. When the magnetic diffusivity is high, the more efficient mechanism for decreasing the disc temperature can be the outflows, and not the large-scale magnetic field. In such a limit of the magnetic diffusivity, the components of the large-scale magnetic field enhance the gas temperature. The increase of temperature can lead to heating and acceleration of the electrons and help us to explain the origin of phenomena such as the flares in Sgr A*. On the other hand, the infall velocity in such a limit rises as the temperature increases, and therefore the surface density falls to too low values. Any change in the density profile can alter the structure and the emitted spectrum of disc.

We report on a preliminary analysis of a 5600 sec per point survey of 32 square degrees in Centaurus, carried out with the Parkes 13-beam system. The signal-to-noise ratio is found to improve as for the whole integration. We have detected 102 HI sources between +250 and +12,700 km s−1 either by eye or by using the new galaxy-finding algorithm PICASSO. Over half of these are new HI detections. Around a dozen of these are not associated with catalogued galaxies and, in two of these cases, we have not identified an optical counterpart on the Digitized Sky Survey. Arguments are put forward to explain why deep integrations are needed to find low surface brightness objects.

We derive transformation equations between GALEX and UBV colours by using the reliable data of 556 stars. We present two sets of equations: as a function of (only) luminosity class and as a function of both luminosity class and metallicity. The metallicities are provided from the literature, while the luminosity classes are determined by using the PARSEC mass tracks in this study. Small colour residuals and high squared correlation coefficients promise accurate derived colours. The application of the transformation equations to 70 stars with reliable data shows that the metallicity plays an important role in estimation of more accurate colours.

A combined multi-station radar equipment of c.w. and pulse at 27 MHz was used at Adelaide (lat. 35°S) during the period December 1968 to June 1969 and again in October 1969 to measure radiants and velocities of individual meteors down to limiting radio magnitude MR = + 8. Reflections from 3 to 5 points typically separated by 2 to 6 km along each trail were used and corrections for the effects of meteor region winds and wind shears were included. To date 1667 orbits have been determined from 6 months of data.

This review is concerned mainly with the solar modulation of galactic cosmic rays and the progress that has been made since the Tenth International Conference on Cosmic Rays (Calgary, June 1967), My aim is to set out some of the advances in the basic theories; to indicate why certain disagreements between convection-diffusion theory and observations (noted in Webber’s invited review at Calgary) are to be expected; and to indicate some of the currently emerging areas of interest.

Many of the X-ray pulsars for which X-ray lightcurves have been presented in the literature exhibit asymmetric emission beams. We postulate the existence of an off-centre magnetic dipole field embedded in the rotating neutron star and show that such a field leads to varying rates of matter transfer between an accretion dise and the neutron star surface, over a rotation period. Assuming that the accretion rate onto the surface is simply related to the luminosity, we show that most of the observed asymmetries can be accounted for by this mechanism.

We have developed water vapour radiometers (WVRs) for the Australia Telescope Compact Array that are capable of determining signal path-length fluctuations by virtue of measuring small temperature fluctuations in the atmosphere using the 22.2-GHz water vapour line for each of the six antennae. By measuring the line-of-sight variations of the water vapour, the induced path excess and thus the phase delay can be estimated and corrections can then be applied during data reduction. This reduces decorrelation of the source signal. We demonstrate how this recovers the telescope's efficiency as well as how this improves the telescope's ability to use longer baselines at higher frequencies, thereby resulting in higher spatial resolution. A description of the WVR hardware design, their calibration, and water vapour retrieval mechanism is given.

Using two volume-limited Main galaxy samples of the Sloan Digital Sky Survey Data Release 7 , we explore influences of galaxy interactions on AGN activity. It is found that in the faint volume-limited sample, paired galaxies have a slightly higher AGN fraction than isolated galaxies, whereas in the luminous volume-limited sample, an opposite trend can be observed. The significance is <1σ. Thus, we do not observe strong evidence that interactions or mergers likely trigger the AGN activity.

The Physics Department at the University of Otago, Dunedin, New Zealand, has over the past three years commenced a research and teaching programme in astronomy and astrophysics. Observing facilities now include two metric wave meridian transit telescopes at a site 6 km from Dunedin and a 16-inch optical telescope, formerly at Mt John, which is now sited 4 km from Dunedin at the Signal Hill observatory built by the University’s Surveying Department for geodetic work.

In this article I review our understanding of s-process nucleosynthesis in Asymptotic Giant Branch (AGB) stars. The discussion begins with the nuclear back~ ground and then shows how the required conditions are found in thermally pulsing AGB stars. The two competing neutron sources (Ne22 and C13) are discussed, as is the observational and theoretical evidence for and against each of them. We conclude by discussing the recent evidence for hot bottom burning, including the observed enhancements of Li7 and Al26 in some AGB stars.

Radio maps of extragalactic radio sources made with the Westerbork, Cambridge and V.L.A. synthesis telescopes have revealed collimated jets extending from the cores to the radio lobes (see Miley 1980 for a review). These observations have provided outstanding support for ‘beam models’ of extragalactic radio sources (Scheuer 1974, Blandford and Rees 1974). Two crucial pieces of information to emerge from high resolution observations are the behaviours of jet full width half maximum (FWHM) and surface brightness with angular distance from the core. Such data have for instance been provided by Formalont et al. (1980) and Bridle et al. (1981) for the jets in 3C-31 and by Willis et al. (1981) and Bridle (1981) for the jets in NGC 315. An important point is that the relationship between jet surface brightness and FWHM is not in general as predicted by simple magnetohydrodynamic models (Bridle 1981).

Ina recent paper, Lockwood et al. (1991) have used IMP spacecraft and Neutron Monitor data to consider the rigidity dependence of three large Forbush Decreases over the energy range 50 MeV to 30 GeV. Some of their conclusions are extrapolated to higher energies.

In an earlier paper (Duldig, 1987a), one of us discussed the need to consider the presence of isotropic intensity waves when determining the Forbush Decrease spectrum at energies up to a few hundred GeV. Lockwood et al.’s conclusions are discussed in the light of these results.

Recent results on NGC 2915, the first blue compact dwarf galaxy to have its mass distribution modelled, are summarised. NGC 2915 is shown to have HI well beyond its detected optical extent. Its rotation curve is well determined and fit with maximum disk mass models. The dark matter halo dominates the mass distribution at nearly all radii, and has a very dense core compared to those of normal galaxies. High-mass star formation energises the HI in the centre of the galaxy, but appears to be maintained in viriai equilibrium with the dark matter halo. The implications of these results are briefly discussed.

The traditional approach to the extragalactic distance scale rests on a pyramid of primary, secondary and tertiary indicators of increasing range and decreasing accuracy. This multi-step procedure, fraught with the danger of cumulative errors, has led in recent years to two main, widely diverging scales: the ‘long’ scale (Sandage and Tammann 1974, 1975, 1976) implying a Hubble constant and the ‘short’ scale (de Vaucouleurs 1978, 1979; de Vaucouleurs and Bollinger 1979; de Vaucouleurs and Peters 1981; de Vaucouleurs et al. 1981) leading to H0 ≃ 100. Several authors have already shown that the long scale rests on very precarious foundations (Capaccioli and Fasano 1980, de Vaucouleurs 1981, Hanes 1980); counter arguments have been offered in its defence and to criticize the short scale (Tammann, Sandage and Yahil 1979, Sandage and Tammann 1982). For want of a conclusive test a consensus was still lacking.

An analysis has been made of events recorded in one year from the direction of the active galaxy Centaurus A using the Buckland Park UHE gamma-ray telescope. No statistically significant excess was observed over this period. Data collected between 1984 and 1989 show evidence for an excess of events from this direction at shower sizes in the range of 2 × 105 to 5 × 105 particles.

A search for Type Ia supernovae at cosmological distances is being undertaken in an attempt to exploit their standard candle property to constrain the mass density of the universe. We describe the rationale for such a program, the observational approach and strategy taken, and the progress made to date. The science that is being generated by the project in additional to supernova detection is also discussed briefly.

Since the discovery of variable circular and linear polarisation in VV Puppis (Tapia 1977), several investigators have observed the system. The new observations particularly of polarisation (Liebert et al. 1978, Liebert and Stockman 1979 have ruled out the standard dwarf nova (accretion disc — hot spot) model previously used to interpret the light curve of VV Puppis.

Over past decades many attempts have been undertaken to detect a statistically significant 11-year variation in tree-ring widths and thereby provide direct evidence for the influence of solar cycle activity on growth. The data were generally associated with arid sites and were found to contain no signal of any consequence at the equivalent frequency. However, our recent analysis of a tree-ring chronology established from spruce trees growing at a very high sub-alpine site in Colorado, has revealed the presence of a dominant 11-year spectral periodicity over the last 200 years. These growth cycles could arise from temperature changes due to variations in insolation and climate or from variations in direct radiation within a specific band.

Active Galactic Nuclei (AGN) occur with widely differing characteristics of luminosity, variability and non-thermal emission. Although it is generally accepted that all such objects are powered by the accretion of matter to a super-massive black hole, no convincing model has been proposed which accounts for the diversity of observed phenomena. The model described here is based upon the hypothesis that shear flows in a misaligned accretion disc around a Kerr black hole lead to the growth of dynamical instabilities which disrupt the disc near the Bardeen-Petterson radius. Resulting clouds of disc material are fragmented by collisions and ablated by radiation from the compact core to produce a hot Parker wind which is optically thick to electron scattering. Within this wind, many fragments of disc material are entrained and photoionised to produce the broad emission lines, while some are accreted to power the system. Usually the wind impedes jet flows, in which case the object is radio quiet. When the disc and black hole are only slightly misaligned, however, the wind is equatorially biased and collimated axial jets may form. Such objects will be radio loud, and may exhibit superluminal phenomena if the jet is oriented close to the line of sight.