High-resolution échelle spectra of 42 nearby southern solar-type stars have been obtained, in a search for young, single, active, and rapidly rotating sun-like stars suitable for Doppler imaging and Zeeman Doppler imaging studies. As a result of this survey, 13 stars were determined to be youthful with ages less than 600 Myr (Hyades age) and eight of these were found to have projected rotational velocities in excess of 15 km s−1. In addition, five spectroscopic binary systems were identified. Of those stars observed for this survey, HD 106506 is the most outstanding target for mapping active regions. It is an apparently young and single star with rapid rotation (v sin i ∼ 80 km s−1), strong Hα chromospheric activity (log R′Hα ∼ −4.2), and deformation of the spectral line profiles indicating the presence of large starspots.

We present results from a new 12CO (J =1→ 0) survey of theλ-Orionis region. The observations cover 110 square degrees uniformly on a Nyquist-sampled grid. We discover CO emission at levels far lower than possible in previous surveys, revealing a structure similar to that seen in IRAS 100μ maps. We derive a total molecular mass of 1·1×104 M☉. A possible explanation for the isolated and localised outbreak of star formation in the region is discussed.

Cen A, at a distance of less than 4 Mpc, is the nearest radio-loud AGN. Its emission is detected from radio to very-high energy gamma-rays. Despite the fact that Cen A is one of the best studied extragalactic objects the origin of its hard X-ray and soft gamma-ray emission (100 keV <E< 50 MeV) is still uncertain. Observations with high spatial resolution in the adjacent soft X-ray and hard gamma-ray regimes suggest that several distinct components such as a Seyfert-like nucleus, relativistic jets, and even luminous X-ray binaries within Cen A may contribute to the total emission in the MeV regime that has been detected with low spatial resolution. As the Spectral Energy Distribution of Cen A has its second maximum around 1 MeV, this energy range plays an important role in modeling the emission of (this) AGN. As there will be no satellite mission in the near future that will cover this energies with higher spatial resolution and better sensitivity, an overview of all existing hard X-ray and soft gamma-ray measurements of Cen A is presented here defining the present knowledge on Cen A in the MeV energy range.

We describe an image timestamp verification system to determine the exposure timing characteristics and continuity of images made by an imaging camera and recorder, with reference to Coordinated Universal Time. The original use was to verify the timestamps of stellar occultation recording systems, but the system is applicable to lunar flashes, planetary transits, sprite recording, or any area where reliable timestamps are required. The system offers good temporal resolution (down to 2 ms, referred to Coordinated Universal Time) and provides exposure duration and interframe dead time information. The system uses inexpensive, off-the-shelf components, requires minimal assembly, and requires no high-voltage components or connections. We also describe an application to load fits (and other format) image files, which can decode the verification image timestamp. Source code, wiring diagrams, and built applications are provided to aid the construction and use of the device.

An imaging technique with sensitivity to short duration optical transients is described. The technique is based on the use of wide-field cameras operating in a drift scanning mode, whereby persistent objects produce trails on the sensor and short duration transients occupy localised groups of pixels. A benefit of the technique is that sensitivity to short duration signals is not accompanied by massive data rates, because the exposure time is much greater than the transient duration. The technique is demonstrated using a pre-prototype system composed of readily available and inexpensive commercial components, coupled with common coding environments, commercially available software, and free web-based services. The performance of the technique and the pre-prototype system is explored, including aspects of photometric and astrometric calibration, detection sensitivity, characterisation of candidate transients, and the differentiation of astronomical signals from non-astronomical signals (primarily glints from satellites in Earth orbit and cosmic ray hits on sensor pixels). Test observations were made using the pre-prototype system, achieving sensitivity to transients with 21-ms duration, resulting in the detection of five candidate transients. An investigation of these candidates concludes they are most likely due to cosmic ray hits on the sensor and/or satellites. The sensitivity obtained with the pre-prototype system is such that, under some models for the optical emission from fast radio bursts (FRBs), the detection of a typical FRB, such as FRB181228, to a distance of approximately 100 Mpc is plausible. Several options for improving the system/technique in the future are described.

We present first results from pilot observations using a phased array feed (PAF) mounted on the Parkes 64-m radio telescope. The observations presented here cover a frequency range from 1 150 to 1 480 MHz and are used to show the ability of PAFs to suppress standing wave problems by a factor of ~10, which afflict normal feeds. We also compare our results with previous HIPASS observations and with previous H i images of the Large Magellanic Cloud. Drift scan observations of the GAMA G23 field resulted in direct H i detections at z = 0.0043 and z = 0.0055 of HIPASS galaxies J2242-30 and J2309-30. Our new measurements generally agree with archival data in spectral shape and flux density, with small differences being due to differing beam patterns. We also detect signal in the stacked H i data of 1 094 individually undetected galaxies in the GAMA G23 field in the redshift range 0.05 ⩽ z ⩽ 0.075. Finally, we use the low standing wave ripple and wide bandwidth of the PAF to set a 3σ upper limit to any positronium recombination line emission from the Galactic Centre of <0.09 K, corresponding to a recombination rate of <3.0 × 1045 s−1.

For many pulsars the integrated or mean pulse profile is highly polarized. Generally linear polarization dominates over circular and there is a continuous variation of position angle through the profile (e.g. Manchester 1971). In most models for the emission process the angle of polarization is related to the (projected) direction of magnetic fields in the source region. Several of the observed properties of pulsars, for example, the mode-changing phenomenon (Backer 1970) and the different spectral index of different components of the intergrated profile (Manchester 1971), suggest that different parts of the integrated profile are emitted in different (though closely related) parts of the source. The different observed position angles across the integrated profile would then result from different projected magnetic field directions in these different parts of the source. For many pulsars the observed position angle variations are closely represented by a path through a radial set of projected field directions such as would be obtained in the vicinity of a magnetic pole (cf. Radhakrishnan and Cooke 1969).

The main features of visual searching for supernovae in other galaxies by amateur astronomers are described, and an outline is given of the results which have been achieved so far by this method. A short comparison is made between visual searching and photographic searching. A more extensive comparison is then made between visual searching for supernovae in Australia, and the work of the Berkeley Automatic Supernova Search at Leuschner Observatory, since 1986. Among the conclusions is the claim that a competent visual observer could produce similar results to those produced by the Berkeley group if a telescope of similar aperture was used for a similar amount of observing time, and from a good observing site. Indeed, visual searching might possibly produce more results, and such a search would only cost a small fraction of what was spent on this automatic search. It would be a worthwhile project to conduct a visual search with a suitably designed 76-cm telescope, or a one metre telescope, over a period of a few years, to see if this conclusion could be supported in practice.

The Parkes 64-m antenna has been used to map ammonia emission in the (J,K = 1,1) and (J,K = 2,2) transitions toward molecular cloud complex NGC 6334. This complex contains a number of OH and H2O masers, HII regions and IR sources, and is a rich source of molecular line emission.

Distributions of observed and derived quantities are presented with a linear resolution of ∼ 1 pc. Velocity anomalies are present near the two OH masers NGC 6334A and B, and the source of ammonia emission located near the northernmost H2O maser is one of the most intense sources of NH3 emission in the Galaxy.

Alignments in the angular momentum vectors of galaxies can induce large scale correlations in their projected orientations. Such alignments arise from the tidal torques exerted on neighboring protogalaxies by the smoothly varying shear field. Weak gravitational lensing can also induce ellipticity correlations since the images of neighboring galaxies will be distorted coherently by the intervening mass distribution. Comparing these two sources of shape correlations, it is found that for current weak lensing surveys with a median redshift of zm = 1, the intrinsic signal is a contaminant on the order of 1–10% of the measured signal. However, for shallower surveys with zm ≤ 0.3, the intrinsic correlations dominate over the lensing signal. The distortions induced by lensing are curl-free, whereas those resulting from intrinsic alignments are not. This difference can be used to disentangle these two sources of ellipticity correlations. When the distortions are dominated by lensing, as occurs at high redshifts, the decomposition provides a valuable tool for understanding properties of the noise and systematic errors.

In 1992 an NRAO 225-GHz site survey heterodyne radiometer was placed at the Geographical South Pole. The instrument operated over an entire annual cycle and provided direct measurements of the millimetre-wave sky brightness temperature as a function of zenith angle. Interpreted in a single-slab ‘skydip’ radiation transfer model of the atmosphere, these sky brightness measurements provided a time series of the millimetre atmospheric opacity. Statistics derived from this opacity time series were important for making comparisons with other candidate millimetre and sub-millimetre wave astronomy sites. This paper reexamines the 1992 measurements and the original analysis. Details of the skydip fit model, radiometer gain error, instrument stability, and a mid-season replacement to a window in the instrument enclosure combined to cause a modest under-reporting of the atmospheric opacity in previous reports. Unchanged are earlier conclusions that dry air makes a significant contribution to the total opacity at 225 GHz.

In this study, a novel machine learning algorithm, restricted Boltzmann machine, is introduced. The algorithm is applied for the spectral classification in astronomy. Restricted Boltzmann machine is a bipartite generative graphical model with two separate layers (one visible layer and one hidden layer), which can extract higher level features to represent the original data. Despite generative, restricted Boltzmann machine can be used for classification when modified with a free energy and a soft-max function. Before spectral classification, the original data are binarised according to some rule. Then, we resort to the binary restricted Boltzmann machine to classify cataclysmic variables and non-cataclysmic variables (one half of all the given data for training and the other half for testing). The experiment result shows state-of-the-art accuracy of 100%, which indicates the efficiency of the binary restricted Boltzmann machine algorithm.

Dependences of electron and proton impact Stark width on the upper level ionization potential within different series of the neutral calcium spectral lines have been evaluated and discussed. The similar dependences previously found for the electron impact contribution were also obtained for the proton impact contribution to the Stark broadening. The emphasis is on the term structure influence on the studied Stark width dependences. The influence of the lower transition level and transition term is higher at low temperatures. After establishing these dependences, predictions were made for Stark widths of neutral calcium spectral lines not measured experimentally or calculated theoretically until now.

We describe bright microwave events that were first detected with the Parkes 64-m telescope at 8.4 or 22 GHz from six active-chromosphere stars. In some flares spectral data were obtained over a large frequency range from simultaneous measurements with the Parkes reflector (8.4 or 22 GHz), the Tidbinbilla interferometer (8.4 and 2.29 GHz), the Fleurs synthesis telescope (1.42 GHz) and the Molonglo Observatory synthesis telescope (0.843 GHz). Data on circular polarization were obtained from the Parkes observations at 8.4 GHz.

The stars were in a wide variety of evolutionary states, ranging from a single pre-main-sequence star (HD 36705), two RS CVn binaries (HD 127535, HD 128171), an Algol (HD 132742) and two apparently single K giants (HD 32918 and HD 196818). Their high brightness temperatures, positive spectral indices and low polarization are consistent with optically thick gyrosynchrotron emission from mildly relativistic electrons with average energies 0.5 to 3 MeV gyrating in inhomogeneous magnetic fields of 5 to 100 G.

The Buckland Park air shower array is being developed particularly for use as an ultra-high-energy gamma ray astronomy telescope. The properties of this instrument are described with an emphasis on improvements being made to its angular resolution. Some early data are presented to illustrate the way in which the data obtained will be used.

Expectations and results of searches at radio and optical wavelengths for a pulsar in SN 1987A are described.

Charles Todd was the first Government Astronomer and Superintendent of Telegraphs in South Australia. Most widely known for his instrumental role in the construction of the Overland Telegraph, linking Australia and England, Todd also established the Adelaide Observatory and made valuable contributions to both astronomy and meteorology.

We present spectropolarimetric observations of the type Ia supernova 1992A obtained 2 weeks and 7 weeks after maximum light. No significant polarisation was detected across any of the spectral features.

In this article, we present a galactic gravitational model of three degrees of freedom (3D), in order to study and reveal the character of the orbits of the stars, in a binary stellar system composed of a primary quiet or active galaxy and a small satellite companion galaxy. Our main dynamical analysis will be focused on the behaviour of the primary galaxy. We investigate in detail the regular or chaotic nature of motion, in two different cases: (i) the time-independent model in both 2D and 3D dynamical systems and (ii) the time-evolving 3D model. For the description of the structure of the 2D system, we use the classical method of the Poincaré (x, px), y = 0, py < 0 phase plane. In order to study the structure of the phase space of the 3D system, we take sections in the plane y = 0 of the 3D orbits, whose initial conditions differ from the plane parent periodic orbits, only by the z component. The set of the four-dimensional points in the (x, px, z, pz) phase space is projected on the (z, pz) plane. The maximum Lyapunov characteristic exponent is used in order to make an estimation of the chaoticity of our galactic system, in both 2D and 3D dynamical models. Our numerical calculations indicate that the percentage of the chaotic orbits increases when the primary galaxy has a dense and massive nucleus. The presence of the dense galactic core also increases the stellar velocities near the center of the galaxy. Moreover, for small values of the distance R between the two bodies, low-energy stars display chaotic motion, near the central region of the galaxy, while for larger values of the distance R, the motion in active galaxies is entirely regular for low-energy stars. Our simulations suggest that in galaxies with a satellite companion, the chaotic nature of motion is not only a result of the galactic interaction between the primary galaxy and its companion, but also a result caused by the presence of the dense nucleus in the core of the primary galaxy. Theoretical arguments are presented in order to support and interpret the numerically derived outcomes. Furthermore, we follow the 3D evolution of the primary galaxy, when mass is transported adiabatically from the disk to the nucleus. Our numerical results are in satisfactory agreement with observational data obtained from the M51-type binary stellar systems. A comparison between the present research and similar and earlier work is also made.

The 2MASS, UKIDSS-LAS, and VISTA VIKING surveys have all now observed the GAMA 9hr region in the Ks band. Here we compare the detection rates, photometry, basic size measurements, and single-component GALFIT structural measurements for a sample of 37 591 galaxies. We explore the sensitivity limits where the data agree for a variety of issues including: detection, star–galaxy separation, photometric measurements, size and ellipticity measurements, and Sérsic measurements. We find that 2MASS fails to detect at least 20% of the galaxy population within all magnitude bins, however for those that are detected we find photometry is robust (± 0.2 mag) to 14.7 AB mag and star–galaxy separation to 14.8 AB mag. For UKIDSS-LAS we find incompleteness starts to enter at a flux limit of 18.9 AB mag, star–galaxy separation is robust to 16.3 AB mag, and structural measurements are robust to 17.7 AB mag. VISTA VIKING data are complete to approximately 20.0 AB mag and structural measurements appear robust to 18.8 AB mag.