A radio-astronomical observation in its most complete form is a determination of intensity and polarization as functions of frequencyf, time t, and position in the sky. An actual observation is usually much less complete.

Savage et al. (1977) found that the radio source PKS 1448-232 coincided with a stellar object of about magnitude 16.4 having an ultraviolet excess. A low resolution spectrum obtained with the Anglo-Australian Telescope (AAT) confirmed this object as a QSO with zem = 2.22 and revealed many absorption lines short-ward of the La emission. Consequently this object was included in a programme of spectroscopy at intermediate resolution with the AAT to investigate QSO absorption lines. Savage et al. have given a finding chart with an optical position of 14h48m09s.3, −23°17′10″ (1950.0). The radio fluxes are 0.40 Jy at 2.7 GHz and 0.31 Jy at 5.0 GHz.

Surface Brightness Fluctuations (SBFs) are one of the most powerful techniques to measure the distance and to constrain the unresolved stellar content of extragalactic systems. For a given bandpass, the absolute SBF magnitude M depends on the properties of the underlying stellar population. Multi-band SBFs allow scientists to probe different stages of the stellar evolution: ultraviolet and blue wavelength band SBFs are sensitive to the evolution of stars within the hot horizontal branch and post-asymptotic giant branch phases, whereas optical SBF magnitudes explore the stars within the red giant branch and horizontal branch regimes. Near- and far-infrared SBF luminosities probe the important stellar evolution stage within the asymptotic giant branch and thermally pulsating asymptotic giant branch phases. Since the first successful application by Tonry and Schneider, a multiplicity of works have used this method to expand the distance scale up to 150 Mpc and beyond. This article gives a historical background of distance measurements, reviews the basic concepts of the SBF technique, presents a broad sample of investigations and discusses possible selection effects, biases, and limitations of the method. In particular, exciting new developments and improvements in the field of stellar population synthesis are discussed that are essential to understand the physics and properties of the populations in unresolved stellar systems. Further, promising future directions of the SBF technique are presented. With new upcoming space-based satellites such as Gaia, the SBF method will remain as one of the most important tools to derive distances to galaxies with unprecedented accuracy and to give detailed insights into the stellar content of globular clusters and galaxies.

As part of a general investigation of interstellar clouds associated with southern HII regions we have begun a high-resolution study of the sodium D-line absorption in the directions of early-type stars that are likely to be associated with or located behind the clouds.

This paper describes a preliminary series of observations of the Sun made at a frequency of 80 MHz with the 3 km radioheliograph of the Culgoora Observatory. The instrument records, at one-second intervals, pictures of the solar image in the form of 60 (E-W) × 48 (N-S) points, each separated in angle by half the Rayleigh limit (2’ arc in the zenith). At the time of the present observations the instrument was incomplete in three main respects : (a) the facilities for recording opposite senses of circular polarization were not available; (b) the automatic image compensation for zenith-angle foreshortening was not available—hence the optical disk of the Sun appears elliptical; and (c) the phase and amplitude calibration procedures had not been fully established, resulting in a higher sidelobe level than that specified in the design—the effects are sometimes evident in the pictures as spoke-like brightenings.

The naked-eye cluster, Messier 7, is situated in the constellation of Scorpius, south of the great Sagittarius star clouds, and close to the galactic centre.

Observations of the solar surface indicate a cellular structure, photospheric granulation, which, as suggested by Wilson and others, could arise from a shallow convection layer. The basic observed granulation pattern has been likened to a hexagonal cell type structure.

The theory of stellar convection zones has met three difficult problems. They are non-linearity, non-locality, and non-greyness of radiative transport. Non-linearity is inherent in turbulence. Non-locality is due to the nature of convection, that larger eddies are apt to be more unstable as indicated by the fourth-power dependence of the Rayleigh number on the vertical dimension. Inhomo-geneity and anisotropy of convection, penetration into stable layers, are the consequences. Non-grey radiative transfer through an eddy element is important in a convective atmosphere. In a preceding paper, the author has developed a theory which includes all these effects, using the representative eddy approximation. The emphasis in that paper was put rather in the non-locality and in the radiative non-greyness ; the treatment of non-linearity has been considered mainly in much earlier investigations. In the present note, we shall study how the representative eddy approximation is reconciled with the spectral theory of turbulence, and we shall determine the effective Reynolds and Péclet numbers, the coupling constants appearing in the eddy transport coefficients.

A major requirement of modern radio astronomy is the attainment of the highest possible angular resolution. This high angular resolution should be matched by a high sensitivity and by spectral and polarization capabilities. Study and experience have shown that no form of telescope is more effective in this respect than the aperture synthesis type. The past few years have seen a growing realization amongst astronomers, both here and overseas, of the need for a new synthesis telescope able to observe the full southern sky. This realization has been stimulated by several factors:

Mount Stromlo Observatory came into being on 1 January 1924. First known as the Commonwealth Solar Observatory, it was founded primarily for studying the Sun and solar-terrestrial relations, though from the outset it was much concerned with various aspects of geophysics. There was also a stellar programme, but after a promising start this had to be discontinued. The solar-geophysical regime continued, with success, until World War II. The Observatory went through the War with a new director, and at the end of it embarked on a new and unfamiliar course to develop into the fully-fledged astrophysical institute it has become today. This transition marks an important chapter in the history of Australian astronomy: I have tried here to describe some of its aspects, as they seemed to me.

The plans of JACARA, the Joint Australian Centre for Astrophysical Research in Antarctica, for Australian involvement in future astronomical activities on the antarctic plateau, are outlined.

The use of artificial neural networks (ANNs) as a classifier of digital spectra is investigated. Using both simulated and real data, it is shown that neural networks can be trained to discriminate between the spectra of different classes of active galactic nucleus (AGN) with realistic sample sizes and signal-to-noise ratios. By working in the Fourier domain, neural nets can classify objects without knowledge of their redshifts.

Following a successful program to investigate the physics of ultra-high-pressure proportional counters, a counter array has been developed for hard X-ray astronomy. A parallel investigation has evaluated the performance of a large-area phoswich scintillator detector for the same purpose. The two detectors have been integrated in a balloon-borne payload, the Astrophysical X-ray Experimental Laboratory (AXEL). This paper describes the instrumentation aboard the payload.

In this paper, a new sparse principal component analysis (SPCA) method, called DCPCA (sparse PCA using a difference convex program), is introduced as a spectral feature extraction technique in astronomical data processing. Using this method, we successfully derive the feature lines from the spectra of cataclysmic variables. We then apply this algorithm to get the first 11 sparse principal components and use the support vector machine (SVM) to classify. The results show that the proposed method is comparable with traditional methods such as PCA+SVM.

There are three distinct types of ‘coherent emission’ in astrophysical plasmas: plasma emission (e.g. in solar radio bursts), electron cyclotron maser emission (e.g. in Jupiter's radio bursts), and pulsar radio emission. The development and current status of our understanding of coherent emission is reviewed, concentrating on plasma emission and electron cyclotron maser emission for which there is direct information on the distributions of electrons that produce the radiation. A generic model for a coherent emission process involves a maser generating radiation in a natural mode of the ambient plasma, and operating near marginal stability. A specific coherent emission mechanism involves the form of free energy to drive the maser, a pump that provides the free energy, and the plasma instability that leads to wave growth. The nature of coherence and its measurement through higher order intensity correlations are discussed.

We present results from a multiwavelength study of the blazar PKS 1954–388 at radio, UV, X-ray, and gamma-ray energies. A RadioAstron observation at 1.66 GHz in June 2012 resulted in the detection of interferometric fringes on baselines of 6.2 Earth-diameters. This suggests a source frame brightness temperature of greater than 2 × 1012 K, well in excess of both equipartition and inverse Compton limits and implying the existence of Doppler boosting in the core. An 8.4-GHz TANAMI VLBI image, made less than a month after the RadioAstron observations, is consistent with a previously reported superluminal motion for a jet component. Flux density monitoring with the Australia Telescope Compact Array confirms previous evidence for long-term variability that increases with observing frequency. A search for more rapid variability revealed no evidence for significant day-scale flux density variation. The ATCA light-curve reveals a strong radio flare beginning in late 2013, which peaks higher, and earlier, at higher frequencies. Comparison with the Fermi gamma-ray light-curve indicates this followed ~ 9 months after the start of a prolonged gamma-ray high-state—a radio lag comparable to that seen in other blazars. The multiwavelength data are combined to derive a Spectral Energy Distribution, which is fitted by a one-zone synchrotron-self-Compton (SSC) model with the addition of external Compton (EC) emission.

The latest generation of radio astronomy interferometers will conduct all sky surveys with data products consisting of petabytes of spectral line data. Traditional approaches to identifying and parameterising the astrophysical sources within this data will not scale to datasets of this magnitude, since the performance of workstations will not keep up with the real-time generation of data. For this reason, it is necessary to employ high performance computing systems consisting of a large number of processors connected by a high-bandwidth network. In order to make use of such supercomputers substantial modifications must be made to serial source finding code. To ease the transition, this work presents the Scalable Source Finder Framework, a framework providing storage access, networking communication and data composition functionality, which can support a wide range of source finding algorithms provided they can be applied to subsets of the entire image. Additionally, the Parallel Gaussian Source Finder was implemented using SSoFF, utilising Gaussian filters, thresholding, and local statistics. PGSF was able to search on a 256GB simulated dataset in under 24 minutes, significantly less than the 8 to 12 hour observation that would generate such a dataset.

We present two absolute magnitude calibrations, MJ and MKs, for red giants with the colour–magnitude diagrams of five Galactic clusters with different metallicities, i.e. M92, M13, M71, M67, and NGC 6791. The combination of the absolute magnitudes of the red giant sequences with the corresponding metallicities provides calibration for absolute magnitude estimation for red giants for a given colour. The calibrations for MJ and MKs are defined in the colour intervals 1.3≤(V−J)0≤2.8 and 1.75≤(V−Ks)0≤3.80 mag, respectively, and they cover the metallicity interval −2.15≤[Fe/H]≤+0.37 dex. The absolute magnitude residuals obtained by the application of the procedure to another set of Galactic clusters lie in the intervals −0.08<ΔMJ≤+0.34 and -0.10< Δ MKs≤ +0.27 mag for MJ and MKs, respectively. The means and standard deviations of the residuals are 〈ΔMJ〉=0.137 and σMJ=0.080, and $〈 Δ MKs〉 =0.109 and σMKs=0.123 mag. The derived relations are applicable to stars older than 4 Gyr, the age of the youngest calibrating cluster.

Metals are found in all baryonic phases and environments, and our knowledge of their distribution ‘in and around galaxies’ has significantly improved over the past few years. Theoretical work has shown that the fraction of metals in different baryonic components can vary significantly when different feedback schemes are adopted. Therefore, studies of element abundances provide important information about all gas-dynamical processes which determine the cosmic evolution of baryons. I give here a brief review of recent observational progress, describe the implications of recent theoretical studies, and discuss briefly future prospects.

This study inspects the light and radial-velocity curves of the eclipsing binary AV Del. In comparison with other studies already done, the study shows that the absolute elements, fundamental orbital and physical parameters of the system can be determined using the Wilson-Devinney code. Using these parameters, the configuration of the system is presented. Then, an accretion disc model for the system is introduced by using the shellspec code. The results indicate that AV Del is a semi-detached system in which an optically thick accretion disc is surrounding the primary star. The outer radius of the disc is 8.0 R⊙, corresponding to a distance of 1.1 R⊙ from the surface of the secondary. Also, the temperature of the disc is calculated to be T = 5700 K.