Photographic observations of Flare Stars in association with Slee, Higgins and Patston, T Association patrols, photographic photometry of selected variable stars in association with Bateson of New Zealand and surveillance of comets brighter than V = 13m, in association with Candy of the United Kingdom constitute the principal fields of research of Page Observatory (private), situated 7 miles North of Brisbane. A recently constructed f2.9 8in/12.5in Schmidt telescope now serves as the main photographic instrument.

The formation of the first stars and galaxies during ‘Cosmic Dawn’ is thought to have imparted a faint signal onto the 21-cm spin temperature from atomic Hydrogen gas in the early Universe. Observationally, an absorption feature should be measurable as a frequency dependence in the sky-averaged (i.e. global) temperature at meter wavelengths. This signal should be separable from the smooth—but orders of magnitude brighter—foregrounds by jointly fitting a log-polynomial and absorption trough to radiometer spectra. A majority of approaches to measure the global 21-cm signal use radiometer systems on dipole-like antennas. Here, we argue that beamforming-based methods may allow radio arrays to measure the global 21-cm signal. We simulate an end-to-end drift-scan observation of the radio sky at 50–100 MHz using a zenith-phased array, and find that the complex sidelobe structure introduces a significant frequency-dependent systematic. However, the $\lambda/D$ evolution of the beam width with frequency does not confound detection. We conclude that a beamformed array with a median sidelobe level ${\sim}-50$ dB may offer an alternative method to measure the global 21-cm signal. This level is achievable by arrays with $O(10^5)$ antennas.

We have used times of maximum light for SX Phe, obtained by ourselves and other workers over 55 years to study the behaviour of the fundamental and first overtone radial pulsation modes of the star. We find (1/P0)dP0/dt to be (+2.53 ± 0.05) × 10−8 yr−1 and (1/P1)dP1/dt to be (−1.60 ± 0.03) × 10−7 yr−1, which differ significantly from the value +1.9 × 10−9 yr−1 expected if the changes are due to standard evolution of the star. The residuals in O–C from a quadratic fit cannot be explained by a light–time effect in a binary. There is some evidence that the amplitudes of the two modes change slowly with time.

The Buckland Park air shower array has been used for some time as an ultra-high-energy gamma-ray telescope operating at photon energies of about 1015 eV. Other such telescopes have reported apparent bursts of events from astrophysical objects under study. We report here searches for UHE bursts from 14 southern hemisphere objects studied in our UHE programme. No conclusive evidence has been found for any UHE burst activity from these sources in the period 1986-1988. There is possible evidence for activity associated with 1700-377 and SN1987A.

The giant radio galaxy B1308–441 has prominent two-sided jets, typical of Fanaroff–Riley class I radio galaxies, but there is an unusual bright spot in the SE jet 2 arcmin from the core that gives a marked asymmetry to the source. Observations at 1·37 and 2·37 GHz with the Australia Telescope Compact Array show that the bright spot has a flattened spectrum and high polarisation, and changes the direction of the SE jet. There is a diffuse optical object close to the bright spot which may be related to a shock in the jet.

Since 1971, the Llanherne low frequency radio telescope (Ellis 1972) has been used to conduct surveys of the sky at several decametric wavelengths. Prior to 1974, only pen recordings on paper chart for one declination at each of the wavelengths were obtained each night and all the work to produce the final sky maps was to have been done by hand. However in 1974, a general purpose digital minicomputer (a Digital Equipment Corporation PDP 8/E) has considerably increased the research capabilities of the telescope. In the continuum sky surveys profiles at several different declinations are now obtained each night. In addition all the information gathered in an observing session is written onto magnetic tape which is later analysed on the University of Tasmania’s computer (an Elliot-503) thus providing the possibility of removing much of the tedious manual work in preparing the final sky maps. This paper describes the system developed by the author which is used by Cane (1975) to obtain the profiles from which the sky maps are being compiled.

The Tidbinbilla NASA Deep Space Network tracking station near Canberra employs 64-m and 34-m antennas for deep space vehicle communication. Regular use is made of the facilities for radio astronomy via a host country agreement between the United States and Australia. To support the expanding astronomical use of the station, and in particular for the Tidbinbilla two-element interferometer (Batty et al. 1977), a small computer was installed early in 1980 to control observations. The system will also be used for as much data analysis as possible to minimize off-site computing.

The present work discusses the use of a weakly-supervised deep learning algorithm that reduces the cost of labelling pixel-level masks for complex radio galaxies with multiple components. The algorithm is trained on weak class-level labels of radio galaxies to get class activation maps (CAMs). The CAMs are further refined using an inter-pixel relations network (IRNet) to get instance segmentation masks over radio galaxies and the positions of their infrared hosts. We use data from the Australian Square Kilometre Array Pathfinder (ASKAP) telescope, specifically the Evolutionary Map of the Universe (EMU) Pilot Survey, which covered a sky area of 270 square degrees with an RMS sensitivity of 25–35 $\mu$Jy beam$^{-1}$. We demonstrate that weakly-supervised deep learning algorithms can achieve high accuracy in predicting pixel-level information, including masks for the extended radio emission encapsulating all galaxy components and the positions of the infrared host galaxies. We evaluate the performance of our method using mean Average Precision (mAP) across multiple classes at a standard intersection over union (IoU) threshold of 0.5. We show that the model achieves a mAP$_{50}$ of 67.5% and 76.8% for radio masks and infrared host positions, respectively. The network architecture can be found at the following link: https://github.com/Nikhel1/Gal-CAM

Some extragalactic supernovae, such as SN 1986J in NGC 891 (Rupen et al. 1987), are unusually strong radio sources. Their radio emission typically peaks a few years after the supernova explodes, and appears to arise from the interaction of the supernova shock with a dense stellar wind shed by the progenitor star. Since two radio-loud and possibly optically faint supernovae have recently been found serendipitously in nearby spiral galaxies, it is possible that such objects are common. If so, this would have important consequences for our understanding of both the chemical enrichment history of galaxies and the radio emission from starburst galaxies. Preliminary results from a survey of nearby spiral galaxies with the Molonglo Observatory Synthesis Telescope (MOST) allow us to make a first estimate of the radio supernova rate. A larger study now in progress will provide a much more sensitive measurement.

The four-fold advantage over a conventional 4 m reflector which naive information theory confers on the 1.2 m UK Schmidt telescope (Dawe and Watson 1982, Watson 1983) is only approachable in practice under certain rather specific conditions. These relate principally to the surface distribution on the sky of the object classes of interest, and the type of detection employed. Clearly, for general survey work with sky-limited photographic detection, the information advantage is high, but it can be demonstrated (Dawe and Watson 1983) that the relatively new technique of multi-object fibre-optics spectroscopy (eg Hill et al. 1980, 1982, Gray 1983, Lund and Enard 1983) with linear detectors offers very high potential in certain regimes of operation. In particular, the UK Schmidt telescope (UKST) equipped with 400 fibre channels has four times the effective light grasp (= number of fibres utilized × aperture) of a 4 m reflector (with a 1 deg field and equipped with any number of fibres) for target objects with surface densities between approximately 1 and 10 per square degree (Dawe and Watson 1983). Objects ranging from galactic variable stars to quasars lie within these limits, but of especial interest are galaxies, whose apparent luminosity function in this range of surface densities runs from magnitudes 15 to 17 (MacGillivray, private communication). Large-scale, medium accuracy (60 km s−1) redshift surveys of galaxies within this magnitude range promise to be extremely fruitful (Davis 1982) and are easily within the reach of the UKST fibre-coupled to a CCD spectrograph (Watson and Dawe 1984).

In this paper we give an account of the corrections that must be made to the formula for the emissivity ηf due to a power-law energy distribution of ultrarelativistic charged particles in a uniform magnetic field B0 in directions well away from the field lines when the effects of upper and lower cut-off values E2 and E1 in the energy distribution are not negligible.

The DEep Near-Infrared Survey of the southern sky (DENIS) will produce an important by-product: a clean, complete view of the local Universe to z ∼ 0·07 for 105 galaxies. We identify the FLAIR multi-fibre system on the UKST as an extremely competitive facility to undertake follow-up spectroscopy for this sample due to the need to cover wide areas of sky and observe thousands of objects to a relatively bright (B < 17·5) magnitude.

We present a study on characterising the light curves of W UMa-type systems gathered from the archive containing 5 years of data observed with the Robotic Optical Transient Search Experiment Telescope (ROTSE-IIId) located in Turkey. A sample of 45 W UMa-type systems was studied on the basis of Fourier decomposition of light curves and some basic geometrical parameters, namely degree of contact (f), mass ratio (q), and orbital inclination (i), as approximated values for these systems were determined. Moreover, methods based on the Fourier transform technique were applied to the discrete data to determine the orbital periods of those systems. Preliminary estimates for the system parameters were presented and compared with the values available in the literature.

A typical stellar spectrogram shows a vast number of spectral lines. Each of these has its characteristic shape and strength which must, in some way, reflect the structure of the atmosphere in which the radiation arose. It seems reasonable that from all this profile data we should be able (and with considerable redundancy) to infer a good deal about the physical structure of the radiating gas, and a major effort has correspondingly been devoted to clarifying the physical basis of spectral line formation, i.e., exactly how the atmospheric structure and the atomic properties are reflected in the line profiles. This problem, however, is far from solved : Few, if any, of the profiles of strong lines can be predicted in detail from model atmospheres, nor have analyses of the profiles yielded unambiguous data on the atmospheric structure. Indeed, as recently as 1967, the participants at a conference in Bilderberg (Holland) concluded that no data at all which had been obtained from line profile analyses was worthy of inclusion in specifying the solar atmospheric model. Evidently, then, the problem of line formation is not trivial ; in this paper we discuss some of the difficulties and review the not inconsiderable progress which has been made in this area of astrophysical research.

Baseline ripple measurements are of two general kinds, those associated with on-source mechanisms and those with off-source mechanisms (Poulton 1974; Morris 1974). We are here principally concerned with on-source baseline ripples, which occur when a strong continuum radio source is present in the beam. The ripples are particularly conspicuous (Padman 1977, 1978) with a large instrument, such as the Parkes 64-m telescope, where the ripple period is rapid. Here baseline uncertainty becomes especially severe for the detection and study of wide lines, such as the H/He complex and the formamide multiplet near 1.54 GHz. Off-source baseline ripples also occur because of other effects, but in principle they can be removed by subtracting a reference-region spectrum taken while tracking the telescope over the same hour-angle range at the same declination under stable conditions. Improvement of the off-source baseline ripple which arises from stray radiation would also be expected to result from the technique described here.

Some years ago the full non-linear equations, within the one mode approximation, describing finite amplitude convection in a compressive medium with polytropic structure were derived (Van der Borght 1977). It is the purpose of the present paper to report on the numerical integrations of these equations and to show how these can be used to construct a convective model of granulation. In this way one may gain some insight into the structure of the outer layers of the Sun.

Several catalogues of radio sources at 408 MHz have been prepared from observations made with the Molonglo cross telescope. These include (in chronological order) ‘The Molonglo Radio Source Catalogue 1’, the MC1, by Davies et al. (1973), the MC2 and MC3 by Sutton et al. (1974), MC4 by Clarke et al. (1976), ‘The Molonglo Deep Sky Survey of Radio Sources’ by Robertson (1977a,b,d) and ‘The Molonglo Reference Catalogue of Radio Sources’ (MRC) by Large et al. (1981). The catalogues MC1-4 cover selected areas of sky to a flux density limit of ~0.2 Jy to 0.3 Jy. The MRC includes extragalactic radio sources between δ = +18° and δ = −85° and is essentially complete at S408 = 1.00 Jy with raany sources to ˜0.7 Jy. The Wyllie (1969a,b) scale of flux density is used throughout.

Pulsar observations will be made with two new general-purpose transit radiotelescopes at present being built near Hobart.

This review surveys some recent observations of polarization in solar spectral lines with emphasis on their theoretical interpretation. Solar optical polarimetry is concerned primarily with measuring solar magnetic fields, a quest which began with Hale’s (1908) observation of Zeeman splitting in a sunspot. Today a wide range of optical polarimeters is used for solar research (see Bauer (1981) for a comprehensive review). For example, a standard magnetograph (Babcock 1953) detects circular polarization in selected wavelength bands in the wings of a Zeeman sensitive line, providing information on the line of sight or longitudinal field component. The most sophisticated instrument is a Stokes polarimeter (e.g. Bauer et al 1980, 1981) which measures with high spectral resolution the profiles of all four Stokes parameters (I,Q,U,V) across a spectral line. Such a device potentially provides all the data needed to infer the vector magnetic field.

The optical spectra of the AM Herculis binaries are characterized by extremely complex emission lines whose profiles can be resolved into at least three components which are formed in different regions of the accretion stream leading from the companion star towards the magnetic white dwarf. We present a theoretical model which localizes the formation region of the broad emission line component and provides information regarding the structure of this emitting region. In our model the particle trajectories are integrated in a Roche potential and the volume between the white dwarf and the companion has been divided into two different regimes of motion. In one region the gas escapes from the secondary near the inner Lagrange point and is accelerated along a straight line towards the white dwarf. In the other region the magnetic field is strong enought to divert the gas out of the orbital plane and to channel it towards the white dwarfs surface. The model has been used to interpret radial velocity and velocity dispersion data from the AM Herculis system E1405-451.