The astronomical technique of gravitational microlensing provides new opportunities to make measurements which are difficult or impossible by other methods, or which are complementary to those obtained more directly. These include detection of dark matter, determination of galactic structure, measurement of limb darkening of stars, and searches for extra-solar planets. The technique is best suited to the southern sky, and several observations have been made from Australasia. A sample of these observations is described here. A case is also made for a telescope at the Antarctic dedicated to gravitational microlensing.

We investigated the space velocity components of 6 610 red clump (RC) stars in terms of vertical distance, Galactocentric radial distance and Galactic longitude. Stellar velocity vectors are corrected for differential rotation of the Galaxy which is taken into account using photometric distances of RC stars. The space velocity components estimated for the sample stars above and below the Galactic plane are compatible only for the space velocity component in the direction to the Galactic rotation of the thin disc stars. The space velocity component in the direction to the Galactic rotation (Vlsr) shows a smooth variation relative to the mean Galactocentric radial distance (Rm), while it attains its maximum at the Galactic plane. The space velocity components in the direction to the Galactic centre (Ulsr) and in the vertical direction (Wlsr) show almost flat distributions relative to Rm, with small changes in their trends at Rm ~ 7.5 kpc. Ulsr values estimated for the RC stars in quadrant 180° < l ⩽ 270° are larger than the ones in quadrants 0° < l ⩽ 90° and 270° < l ⩽ 360°. The smooth distribution of the space velocity dispersions reveals that the thin and thick discs are kinematically continuous components of the Galaxy. Based on the Wlsr space velocity components estimated in the quadrants 0° < l ⩽ 90° and 270° < l ⩽ 360°, in the inward direction relative to the Sun, we showed that RC stars above the Galactic plane move towards the North Galactic Pole, whereas those below the Galactic plane move in the opposite direction. In the case of quadrant 180° < l ⩽ 270°, their behaviour is different, i.e. the RC stars above and below the Galactic plane move towards the Galactic plane. We stated that the Galactic long bar is the probable origin of many, but not all, of the detected features.

Pulsars have been studied extensively over the last few decades and have proven instrumental in exploring a wide variety of physics. Discovering more pulsars emitting at low radio frequencies is crucial to further our understanding of spectral properties and emission mechanisms. The Murchison Widefield Array Voltage Capture System (MWA VCS) has been routinely used to study pulsars at low frequencies and discover new pulsars. The MWA VCS offers the unique opportunity of recording complex voltages from all individual antennas (tiles), which can be off-line beamformed or correlated/imaged at millisecond time resolution. Devising imaged-based methods for finding pulsar candidates, which can be verified in beamformed data, can accelerate the complete process and lead to more pulsar detections. Image-based searches for pulsar candidates can reduce the number of tied-array beams required, increasing compute resource efficiency. Despite a factor of $\sim$4 loss in sensitivity, searching for pulsar candidates in images from the MWA VCS, we can explore a larger parameter space, potentially leading to discoveries of pulsars missed by high-frequency surveys such as steep spectrum pulsars, exotic binary systems, or pulsars obscured in high-time resolution time series data by propagation effects. Image-based searches are also essential to probing parts of parameter space inaccessible to traditional beamformed searches with the MWA (e.g. at high dispersion measures). In this paper we describe the innovative approach and capability of dual-processing MWA VCS data, that is forming 1-s visibilities and sky images, finding pulsar candidates in these images, and verifying by forming tied-array beam. We developed and tested image-based methods of finding pulsar candidates, which are based on pulsar properties such as steep spectral index, polarisation and variability. The efficiency of these methodologies has been verified on known pulsars, and the main limitations explained in terms of sensitivity and low-frequency spectral turnover of some pulsars. No candidates were confirmed to be a new pulsar, but this new capability will now be applied to a larger subset of observations to accelerate pulsar discoveries with the MWA and potentially speed up future searches with the SKA-Low.

It is shown that for moderately hot polar caps (with effective temperature of ∼106 K), the efficiency of polar gap acceleration is lower compared to the case in which the polar caps are relatively cool and inverse Compton scattering plays no role in controlling the gap. For young pulsars with superstrong magnetic fields (≥109 T) and hot polar caps (with temperature of ≥5 × 106 K), because of the energy loss of electrons or positrons due to resonant inverse Compton scattering in the vicinity of polar caps, pair cascades occur at distances further away from the polar cap, and in this case we have a relatively high acceleration efficiency, with ions carrying most of the particle luminosity.

We present the results of a search for additional exoplanets in all multiplanetary systems discovered to date, employing a logarithmic spacing between planets in our Solar System known as the Titius–Bode (TB) relation. We use the Markov Chain Monte Carlo method and separately analyse 229 multiplanetary systems that house at least three or more confirmed planets. We find that the planets in $\sim 53\%$ of these systems adhere to a logarithmic spacing relation remarkably better than the Solar System planets. Using the TB relation, we predict the presence of 426 additional exoplanets in 229 multiplanetary systems, of which 197 candidates are discovered by interpolation and 229 by extrapolation. Altogether, 47 predicted planets are located within the habitable zone of their host stars, and 5 of the 47 planets have a maximum mass limit of 0.1–2 ${\rm M}_{\oplus}$ and a maximum radius lower than 1.25 ${\rm R}_{\oplus}$ . Our results and prediction of additional planets agree with previous studies’ predictions; however, we improve the uncertainties in the orbital period measurement for the predicted planets significantly.

Traditional HI surveys of optically selected elliptical galaxies are time-consuming, and have a low detection rate. The forthcoming Parkes HI multibeam survey offers the exciting possibility of surveying more than 10,000 nearby elliptical galaxies for HI. I argue that this is likely to result in the detection of a large population of small, HI-rich elliptical galaxies which have not previously been studied in any systematic way.

The dominant process in the evolution of spiral galaxies like our own is clearly the formation of new stars, and the leading optical indicator of this is Hα emission. Considering the tremendous importance of star formation and its variation within and between galaxies, it is surprising just how little survey work has been carried out at Hα. After the successful development of Tech Pan films for deep photographic imaging with the UKST, and given the particular sensitivity of Tech Pan at wavelengths near Hα, it was natural to consider the possibilities for a narrowband Hα imaging survey of large angular extent. This idea quickly developed into a full-blown survey of the whole of the Southern Milky Way, of the Magellanic Clouds, and of selected extragalactic regions of interest such as that around the Virgo Cluster. This special issue is devoted to the discussion of the details of making and using this survey.

The Edinburgh-Cape Bright QSO Survey is a very small sub-set of the Edinburgh Cape Blue Object Survey, which is a major survey to discover blue stellar objects brighter than B~18 in the southern sky. It will cover an area of sky of 10,000 square degrees with |b|>30 and dec <0. The blue stellar objects are selected by automatic techniques from U and B pairs of UK Schmidt Telescope plates scanned with the COSMOS measuring machine. Follow-up photometry and spectroscopy is being obtained with the SAAO telescopes to classify the types of objects brighter than B=16.5, with some of the more stubborn objects being subjected to AAO service spectroscopy. Some preliminary results for the 6% QSO minority are presented in this paper and comparison is made with the Palomar-Green QSO Survey in the north, which we find to be at least a factor of two incomplete.

The absorption counterpart of curvature emission is reexamined based on the Landau-Lifshitz approach. Early derivations led to the conclusion that maser emission is not possible, but these early derivations neglected a drift effect which was first discussed by Zheleznyakov and Shaposhnikov. When the drift effect is included, the derivation implies that curvature maser emission is possible. It is shown that for maser emission to be possible, the Lorentz factor needs to satisfy γ ≳ 103 for radius of curvature of the magnetic field lines RB ≈ 106 to 109cm and frequency ω ≈ 107 to 1011 s−1. Possible application to pulsars is discussed.

We present changes in the periods of the double-mode beat cepheid star SX Phe from 1951 to 1987 deduced from observed times of maximum light.

The exact formula for the intensity of synchrotron radiation emitted by a single charged particle in vacuo was given by Schott, for the case of circular orbits, and Takakura for the case of helical orbits. In the general case the radiated power is expressed in terms of four variables which appear in (among other places) the arguments or orders of a Bessel function and its first derivative; hence the general formula gives little insight into the interpretation of synchrotron radiation and allows evaluation only in particular cases. There is a particular need for approximate formulae that yield the spectrum of the radiation in explicit form. Such approximate formulae were found by Vladimirskii and Schwinger for the case of highly relativistic electrons. In the present paper we outline the derivation of approximate formulae applicable to mildly relativistic electrons, especially those with velocity βc such that 0 ≪ β ≲ O.9. These approximations are also relevant to the case of highly relativistic electrons in a plasma with refractive index appreciably less than unity.

It is the usual practice during continuum radio observations at Parkes to observe ‘pointing sources’ concurrently with the program objects.

We have used rocket-borne photometers to determine the ultra-violet flux of the full moon in the wavelength range 2400-2900A where atmospheric ozone prevents ground-based observations. The lunar fluxes determined in two rocket firings from Woomera on 9th December, 1965, and 30th August, 1966, are summarized in the Table. The results for the two firings have been corrected to full moon values on the assumption that the lunar phase law is the same at these ultra-violet wavelengths as it is in the visible.

In solar physics a need exists for filters which have very narrow passbands, ~0.01 nm or less. While Lyot-Öhman birefringent filters have been used particularly for investigations at the Hα line, the limited availability of the raw materials, especially calcite, have usually restricted these filters to passbands of ~ 0.025 nm or more. A possible alternative type of filter consists of a number of Fabry-Perot interferometers mounted one behind the other.

A theory of linear acceleration emission, with possible application to pulsars, is developed. The equation of motion for a relativistic charged particle accelerated in the field of a longitudinal wave is solved to first order in the electric potential and used to derive the first order current. The power emitted and the absorption coefficient are calculated and the conditions under which masing can occur are discussed.

On 1922 August 20, a 20-strong scientific team, together with a naval party of 10, left Fremantle on one of the major scientific expeditions in Western Australian history. After picking up further personnel at Broome, the party proceeded to the isolated post and telegraph station of Wallal on the northern coast of Western Australia. Their task was to measure with great care the deflection of starlight by the Sun during the total solar eclipse of 1922 September 21. Specially designed photographic equipment of very high quality was used and meteorological conditions were excellent. As a result, measurements were obtained for well over a hundred stars.

The completion of the Uhuru (Forman et al. 1978) and Ariel V (Cooke et al. 1978) surveys of the sky for X-ray emission has resulted in many proposed identifications with individual galaxies and clusters of galaxies. The X-ray positions are not usually accurate enough to enable a positive identification to be made of the X-ray sources with optical or radio objects, and hence the identification is often based on statistical arguments — viz., the unexpected occurrence of unusual galaxies, radio sources or clusters of galaxies within or near the X-ray error boxes. There is usually no significant information available on the angular size of the X-ray emitter but in two or three cases (e.g. Perseus cluster, Coma cluster and Virgo cluster) the angular resolution is good enough to identify a broad component with dimensions approaching those of the whole cluster. This extended X-ray emission has been ascribed to either inverse Compton scattering of the 3° microwave background by relativistic electrons in the intra-cluster medium or to thermal-bremsstrahlung emission by an optically thin plasma at - 10s K.

We resolve a conflict in the literature concerning the effect of induced Compton scattering on the propagation of radio waves through the electron–positron wind surrounding a pulsar.

We present some preliminary results of an optical and radio study of the very active RS CVn binary HD 127535. Photometric measurements show the presence of a large amplitude wave which exhibits marked changes in shape and range on time scales as short as a few months. This photometric variation is almost certainly due to large cool starspots on the cooler, more luminous component. As part of a survey of southern active-chromosphere stars with the Parkes radio telescope, HD 127535 has been observed at 5, 8.4 and 22 GHz. No detection was made at 5 GHz, possibly because of confusion due to the angular proximity of the star to the galatic plane. However, it is one of the strongest sources detected in the 8.4 GHz survey, and is one of only two stars detected at 22 GHz. Photometry obtained two cycles before the 8.4 GHz observations suggest a possible correlation between the radio emission and the photometric wave, i.e. spot visibility, but more data are needed.

Mt John Observatory photographic spectra of SN 1987A have been obtained on 111 nights during the first year at resolutions of 1.1 Å (blue) and 1.6 Å (red). The early spectra are dominated by broad P Cygni profiles from neutral or singly ionised species. Ba absorption lines may be present. After six months nebular emission features emerged, including [OI] 630, 636 nm and two unidentified UV lines (367, 375 nm) in the previously dark region below 380 nm. Absorption line radial velocities show steep declines in the first month, but are almost constant or only slowly decline after 100 days. For the Hα absorption minimum the initial decline rate was 690 ± 70 km s−1d−1 and the initial velocity was −20.2±0.5 Mm s−1 (LMC frame). By 1988 Feb the slowest material in absorption was at −2.2 Mm s−1.

The emission maxima of Hα and NaID show anomalous redshifts of about 1.0 Mm s−1. The [OI] lines show no such redshift. Recent [OI] and Hα spectra at higher resolution show ‘fine structure’ in the profiles, indicating inhomogeneity in the ejecta. Hβ, Hγ and Hδ (but not Hα) were all weaker or absent from 1987 late March to early May, but strong thereafter. From about 1987 Mar 18 to Apr 17 Hα showed a bump on the blue side of the emission at 647 nm and a double peak (658 and 668 nm). Absorption bumps in the Hα profile in early spectra (1987 Feb) may be due to circumstellar water vapour.