We report the development of a radio-linked interferometer which uses the 64-m telescope at Parkes, NSW, and one of the NASA antennas (64-m or 34-m) at Tidbinbilla, ACT. With a baseline of approximately 275 km, this is the world’s longest real-time interferometer; it will be usable at frequencies of 1.6, 2.3, 8.4, and 22 GHz to give angular resolutions of 0.13, 0.09, 0.03, and 0.01 arcsec respectively. The interferometer has already operated successfully in a limited mode and is expected to become fully operational in its initial configuration by September 1985. Operation at a range of frequencies and with progressive enhancements is planned up to the commissioning of the Australia Telescope in 1988.

Shock drift acceleration of the electrons which produce herringbone structure in type II bursts is considered. A non-coplanar component of the magnetic field within the shock front and an electric field across the shock are taken into account. A quantitative difficulty with shock drift acceleration is identified, and possible ways of overcoming the difficulty are outlined.

Analysis of surface and underground detector data from Mawson and Hobart for the period 1982 to 1988 has revealed a number of episodes of enhanced diurnal variation lasting more than 5 days. A preliminary study of these enhancements shows that variations in the rigidity spectrum and in the upper limiting rigidity must be present to explain the phenomenon.

Recent X-ray observations by Jiang et al. have identified an active galactic nucleus (AGN) in the bulgeless spiral galaxy NGC 3319, located just $14.3\pm 1.1$ Mpc away, and suggest the presence of an intermediate-mass black hole (IMBH; $10^2\leq M_\bullet/\textrm{M}_{\odot}\leq 10^5$ ) if the Eddington ratios are as high as 3 to $3\times10^{-3}$ . In an effort to refine the black hole mass for this (currently) rare class of object, we have explored multiple black hole mass scaling relations, such as those involving the (not previously used) velocity dispersion, logarithmic spiral arm pitch angle, total galaxy stellar mass, nuclear star cluster mass, rotational velocity, and colour of NGC 3319, to obtain 10 mass estimates, of differing accuracy. We have calculated a mass of $3.14_{-2.20}^{+7.02}\times10^4\,\textrm{M}_\odot$ , with a confidence of 84% that it is $\leq $ $10^5\,\textrm{M}_\odot$ , based on the combined probability density function from seven of these individual estimates. Our conservative approach excluded two black hole mass estimates (via the nuclear star cluster mass and the fundamental plane of black hole activity—which only applies to black holes with low accretion rates) that were upper limits of ${\sim}10^5\,{\textrm M}_{\odot}$ , and it did not use the $M_\bullet$ – $L_{\textrm 2-10\,\textrm{keV}}$ relation’s prediction of $\sim$ $10^5\,{\textrm M}_{\odot}$ . This target provides an exceptional opportunity to study an IMBH in AGN mode and advance our demographic knowledge of black holes. Furthermore, we introduce our novel method of meta-analysis as a beneficial technique for identifying new IMBH candidates by quantifying the probability that a galaxy possesses an IMBH.

We present infrared imaging from IRIS2 on the Anglo–Australian Telescope that shows the barred spiral galaxy IC 4933 has not just an inner ring encircling the bar, but also a star-forming nuclear ring 1.5 kpc in diameter. Imaging in the u′ band with GMOS on Gemini South confirms that this ring is not purely an artifact due to dust. Optical and near-infrared colours alone however cannot break the degeneracy between age, extinction, and burst duration that would allow the star formation history of the ring to be unraveled. Integral field spectroscopy with the GNIRS spectrograph on Gemini South shows the equivalent width of the Paβ line to peak in the north and south quadrants of the ring, indicative of a bipolar azimuthal age gradient around the ring. The youngest star-forming regions do not appear to correspond to where we expect to find the contact points between the offset dust lanes and the nuclear ring unless the nuclear ring is oval in shape, causing the contact points to lead the bar by more than 90°.

In Paper I, we presented an overview of the Southern-sky MWA Rapid Two-metre (SMART) survey, including the survey design and search pipeline. While the combination of MWA’s large field-of-view and the voltage capture system brings a survey speed of ${\sim} 450\, {\textrm{deg}}^{2}\,\textrm{h}^{-1}$, the progression of the survey relies on the availability of compact configuration of the Phase II array. Over the past few years, by taking advantage of multiple windows of opportunity when the compact configuration was available, we have advanced the survey to 75% of the planned sky coverage. To date, about 10% of the data collected thus far have been processed for a first-pass search, where 10 min of observation is processed for dispersion measures out to 250 ${\textrm{pc cm}}^{-3}$, to realise a shallow survey that is largely sensitive to long-period pulsars. The ongoing analysis has led to two new pulsar discoveries, as well as an independent discovery and a rediscovery of a previously incorrectly characterised pulsar, all from ${\sim} 3\% $ of the data for which candidate scrutiny is completed. In this sequel to Paper I, we describe the strategies for further detailed follow-up including improved sky localisation and convergence to timing solution, and illustrate them using example pulsar discoveries. The processing has also led to re-detection of 120 pulsars in the SMART observing band, bringing the total number of pulsars detected to date with the MWA to 180, and these are used to assess the search sensitivity of current processing pipelines. The planned second-pass (deep survey) processing is expected to yield a three-fold increase in sensitivity for long-period pulsars, and a substantial improvement to millisecond pulsars by adopting optimal de-dispersion plans. The SMART survey will complement the highly successful Parkes High Time Resolution Universe survey at 1.2–1.5 GHz, and inform future large survey efforts such as those planned with the low-frequency Square Kilometre Array (SKA-Low).

We have realised a simple prototype system to perform searches for short timescale optical transients, utilising the novel drift scan imaging technique described by Tingay (2020). We used two coordinated and aligned cameras, with an overlap field of view of approximately 3.7 deg$^2$, to capture over $34\,000 \times 5$ second images during approximately 24 h of observing. The system is sensitive to optical transients, due to an effective exposure time per pixel of 21 ms, brighter than a V magnitude of 6.6. In our 89.7 deg$^2$ h of observations, we find no candidate astronomical transients, giving an upper limit to the rate of these transients of 0.8 per deg$^2$ per day, competitive with other experiments of this type. The system is triggered by reflections from satellites and various instrumental effects, which are easily identifiable due to the two camera system. The next step in the development of this promising technique is to move to a system with larger apertures and wider fields of view.

We investigate the optimal tradeoff between sensitivity and field of view in surveys for slow radio transients using the event detection rate as the survey metric. This tradeoff bears implications for the design of surveys conducted with upcoming widefield radio interferometers, such as the ASKAP VAST survey and the MeerKAT TRAPUM survey. We investigate (i) a survey in which the events are distributed homogeneously throughout a volume centred on the Earth, (ii) a survey in which the events are homogeneously distributed, but are only detectable beyond a certain minimum distance, and (iii) a survey in which all the events occur at an identical distance, as is appropriate for a targetted survey of a particular field which subtends Npoint telescope pointings. For a survey of fixed duration, Tobs, we determine the optimal tradeoff between number of telescope pointings, N, and integration time per field. We consider a population in which the event luminosity distribution follows a power law with index − α, and tslew is the slewing time between fields or, for a drift scan, the time taken for the telescope drift by one beamwidth. Several orders of magnitude improvement in detection rate is possible by optimization of the survey parameters. The optimal value of N for case (i) is Nmax ~ Tobs/4tslew, while for case (iii) we find Nmax = (Lmax/L0)2[(3 − α)/2]2/(α − 1), where Lmax is the maximum luminosity of a transient event and L0 is the minimum luminosity event detectable in an integration of duration Tobs. (The instance Nmax > Npoint in (iii) implies re-observation of fields over the survey area, except when the duration of transient events exceeds that between re-observations of the same field, where Nmax = Npoint applies instead.) We consider the balance in survey optimization between telescope field of view, Ω, and sensitivity, characterised by the minimum detectable flux density, S0. For homogeneously distributed events (i), the detection rate scales as NΩS−3/20, while for targetted events (iii) it scales as NΩS1 − α0. However, if the targetted survey is optimised for N the event detection rate scales instead as ΩS−20. This analysis bears implications for the assessment of telescope designs: the quantity ΩS−20 is often used as the metric of telescope performance in the SKA transients literature, but only under special circumstances is it the metric that optimises the event detection rate.

In this paper, we give arguments that there are two types of coronal mass ejection (CME).The first type of CME discussed here is the ‘loop-type’, whose occurrence is related to an arcade flare somewhere between the footpoints. It was found that there were pre-event magnetic connections between the flare location and the locations of the footpoints of a CME of this type, and that these connections disappeared after the event. This suggests that the footpoints of loop-type CMEs are special prescribed points, and this was verified by the observation that the footpoints do not move in this type of CME.

The other type of CME is the ‘bubble-type’, which is associated with the flare blast from explosive flares. We confirmed the association of this type of CME with the so-called EIT (Extreme Ultra-violet Imaging Telescope) waves, but the velocity of expansion of the bubble is twice or more greater than that of the EIT waves depending on events. Although EIT waves were widely considered to be Moreton waves viewed by SoHO/EIT in the solar activity minimum period, recent simultaneous observations of both have revealed that the EIT wave is something different from the Moreton wave, and propagates separately with a velocity less than half that of a Moreton wave.We therefore propose a new overall picture: the bubble-type CMEs are the flare-produced MHD blast waves themselves, whose skirt is identified as a Moreton wave. EIT waves may be interpreted as follows: the slow-mode gas motions from the source cause secondary longwavelength fast-mode waves which are trapped in the “waveguide” in the low corona. The secondary long-wavelength wave in the fast-mode, which is trapped in the low corona, has a slower propagation velocity due to the nature of the waves trapped in a “waveguide”. This trapped wave induces slow-mode motions of the gas through a mode-coupling process in the high chromosphere, where the propagation velocities of the fastand slow-mode waves match.

Three-dimensional MHD simulations for these two types of CME are in progress, and are previewed in this paper.

A search for planetary nebulae was carried out using candidates selected by their infrared colours and 5 GHz radio emission. One new planetary nebula was identified on the basis of its small angular size, strong [O iii] emission and infrared colours. Another object, known as the possible planetary nebula Wray 16–28, is similarly identified as a planetary nebula. An undiscovered AGN was also found, and is classed as a Seyfert 2 galaxy on the basis of its strong O iii emission, linewidths of ∼500 km s−1, and 5 GHz radio flux. Low-resolution optical spectra are presented and distance estimates discussed.

Orbital-period variations of the neglected W UMa-type binary star, NY Lyr, were analyzed based on two newly determined eclipse times together with the others compiled from the literature. A cyclic oscillation with a period of 82.1 yr and an amplitude of 0.0247 d was discovered to be superimposed on a continuous period increase (dP/dt = +1.33 × 10−7 d yr−1). After the long-term period increase and the large-amplitude cyclic oscillation were removed from the O–C diagram, the residuals suggest that there is another small-amplitude period oscillation (A4 = 0.0053 d, P4 = 19.4 years) in the orbital period changes. As in the cases of AH Cnc and AD Cnc, both the continuous period increase and the two cyclic period oscillations make NY Lyr an interesting system to study in the future. In order to understand the evolutionary state of the binary system, new photometric and spectroscopic observations and a careful investigation on those data are needed.

A simple model of cosmic ray electron acceleration at the jet boundary yields a power law particle energy distribution of ultra-relativistic electrons with an energy cut-off growing with time, and, finally, a growing particle bump at the energy where energy gains equal radiation losses. For such electron distribution, in tens-of-kpc scale jets, we derived the observed time-varying spectra of synchrotron and inverse Compton radiation, including Comptonisation of synchrotron and cosmic microwave background photons. Slowly varying spectral index along the jet in the ‘low frequency’ spectral range is a natural consequence of boundary layer acceleration. Variations of the high energy bump of the electron distribution can give rise to anomalous behaviour in the X-ray band in comparison to the lower frequencies.

First multi-colour complete light curves and low-resolution spectra of short-period eclipsing binary TT Cet are presented. The stellar atmospheric parameters of the primary star were derived through spectra fitting as: $T_{eff}=7\,091\pm124\,{\text{K}}$, $\log g = 4.15\pm0.33\,{\text{cm}}/\text{s}^2$, and $[Fe/H]=-0.23\pm0.04\,\text{dex}$. The light curves were analysed using the Wilson–Devinney code. The photometric solution suggests that this target should be a near-contact binary with the primary component filling its critical Roche lobe (i.e. SD1-type NCB). The luminosity enhancement around the primary light maximum (phase 0.10–0.40) on the light curve was detected like other SD1-type NCBs, which could be caused by a hot spot near the facing surface of the secondary component due to mass transfer. Long-term decrease of the orbital period at a rate of $dP/dt=-5.01\,({\pm}0.06)\times 10^{-8}\,{{\text{d}} \cdot{yr}}^{-1}$ was detected by the O–C analysis, which supports the mass transfer from the primary to the secondary and is consistent with its primary filling configuration. No third body was found through the light curve and O–C analysis. TT Cet may locate in the broken contact stage predicted by the thermal relaxation oscillation theory (TRO) and will evolve to the contact stage eventually. It is another good observational example supporting the TRO theory. We have collected all known SD1-type NCBs with absolute parameters from the literatures. The relations of these parameters are summarised for these rare systems.

The physical properties and spatial distribution of 12 pulsars discovered with the Molonglo radio telescope have been discussed by Mills. Several more pulsars have been detected and details will be published when the measurements are complete. Parameters of a recently discovered pulsar, MP 0628, are given in Table I. All the Molonglo pulsars have been found by visual examination of chart records. The use of pulse lengthening circuits to improve the visibility of pulsars on slow charts, and the continuation of the observations over several hundred hours with the greatest available sensitivity have been factors contributing significantly to the success of the Molonglo pulsar search.

The baseline of East-West array of the Fleurs Synthesis Telescope (FST) has been extended from 786 metres to 1585 metres by the addition of two 13.7 metre dishes. A digital receiver has been built to accommodate the extra delay and correlation requirements, low noise FET preamplifiers have been installed on the large antennas, and a software package has been developed for processing observation data on a VAX 11/780. The FST is now capable of producing accurate wide field maps at 1415 MHz with a resolution of 20 arc seconds and a sensitivity of several milliJansky.

For more than half a century the theory that the universe is expanding has dominated cosmology. All current cosmological theories, from the various Big Bang models to the various Steady State models, explicitly assume an expanding universe. The evidence in favour of an expanding universe is purely circumstantial, and is based on a “sheer assumption”, (Hubble 1936a) that red-shifts in the light received by an observer on Earth from distant objects are caused by relative motion and hence may be interpreted as Doppler shifts. Hubble (1936b) continues: “…the ever expanding model … seems rather dubious”, and “On the other hand, if the recession factor is dropped, if red-shifts are not primarily velocity-shifts, the picture is simple and plausible. There is no evidence of expansion and no restriction of time-scale, no trace of spatial curvature and no limitations of spatial dimensions.” (Hubble 1936c). These statements are as true today as they were in 1936.

A software package called ERIC is described that provides a framework for allowing scientific instruments to be remotely controlled via the Internet. The package has been used to control four diverse astronomical instruments, and is now being made freely available to the community. For a description of ERIC’s capabilities, and how to obtain a copy, see the conclusion to this paper.

The stability of a swirling cylindrical jet of compressible fluid is examined by performing a normal mode analysis and numerically solving the eigenvalue problem. Perturbations of the form f(r)exp[i(ωt-mϕ-kz)] are considered, where f is any fluid variable. Instabilities which are characteristic of both a non-swirling (top-hat) jet and a Rankine vortex are investigated for a particular axial wavenumber.

The vortex instabilities are weak, and are found to remain weak when axial flow is present. The jet instabilities are much stronger, but axial flow is a stabilizing influence. The positive helicity (km > 0) non-axisymmetric modes (m ≠ 0) are stabilized by a small component of azimuthal flow. The axisymmetric mode (m = 0) and the negative helicity non-axisymmetric modes persist in rapidly swirling jets, but with a greatly reduced growth rate.

An instrument is described that can detect clouds at night-time by sensing their infrared emission. The device can readily detect clouds that are difficult to see with the unaided eye on a moon-lit night. It can be used to provide an indication of how photometric the conditions are, to terminate exposures when cloud forms, and to close the dome when conditions become unsuitable for observing. The detector also has applications as an astronomical site-surveying instrument.

In addition to large numbers of normal galaxies, the multibeam HI Parkes all-sky survey will probably discover intergalactic HI clouds, very low-surface-brightness, gas-rich galaxies, and small HI clouds in nearby groups of galaxies. I will briefly discuss some aspects of why these classes of objects are interesting in the context of dark matter and galaxy formation.