Statistical information on 8280 individual radio observations of binary stars, predominantly at 8·4 GHz using the Parkes 64 m antenna, is presented. Three main groups are distinguished: (i) RS CVn stars, (ii) classical Algol binaries (EA2s), and (iii) detached pairs of generally early type (ETBs).

The RS CVn stars more frequently gave rise to detectable fluxes, while the ETBs, in these data, are a small and rather heterogeneous class. The Algols' emission appears to increase near conjunction phases, though we cannot clearly distinguish any special property of the Algols' phase-dependent behaviour that is not also shared by the RS CVn binaries. Both these categories' data show a bimodal, phase-dependent pattern to the distribution of detections, suggesting that these binary types share similar underlying physical properties, though there could also be other factors at play. The sample sizes of the Algols and particularly the ETB detections are too small for effective, discriminatory statistics, however.

The high spatial resolution of the Chandra X-ray Observatory allows us to study the environment of GPS/CSS sources to within an arcsec of the strong compact core. We present the discovery of X-ray jets in two GPS quasars, PKS1127–145 and B2 0738+313, indicating that X-ray emission associated with the relativistic plasma is present at large distances from the GPS nucleus. We also discuss first results from Chandra observations of our GPS/CSS sample. We find that six out of ten sources show intrinsic absorption at a level which may be sufficient to confine the GPS source.

We have observed the G23 field of the Galaxy AndMass Assembly (GAMA) survey using the Australian Square Kilometre Array Pathfinder (ASKAP) in its commissioning phase to validate the performance of the telescope and to characterise the detected galaxy populations. This observation covers ~48 deg2 with synthesised beam of 32.7 arcsec by 17.8 arcsec at 936MHz, and ~39 deg2 with synthesised beam of 15.8 arcsec by 12.0 arcsec at 1320MHz. At both frequencies, the root-mean-square (r.m.s.) noise is ~0.1 mJy/beam. We combine these radio observations with the GAMA galaxy data, which includes spectroscopy of galaxies that are i-band selected with a magnitude limit of 19.2. Wide-field Infrared Survey Explorer (WISE) infrared (IR) photometry is used to determine which galaxies host an active galactic nucleus (AGN). In properties including source counts, mass distributions, and IR versus radio luminosity relation, the ASKAP-detected radio sources behave as expected. Radio galaxies have higher stellar mass and luminosity in IR, optical, and UV than other galaxies. We apply optical and IR AGN diagnostics and find that they disagree for ~30% of the galaxies in our sample. We suggest possible causes for the disagreement. Some cases can be explained by optical extinction of the AGN, but for more than half of the cases we do not find a clear explanation. Radio sources aremore likely (~6%) to have an AGN than radio quiet galaxies (~1%), but the majority of AGN are not detected in radio at this sensitivity.

The detection of a neutron star merger by the Advanced Laser Interferometer Gravitational-Wave Observatory and Advanced Virgo gravitational wave detectors, and the subsequent detection of an electromagnetic counterpart have opened a new era of transient astronomy. With upgrades to the Advanced Laser Interferometer Gravitational-Wave Observatory and Advanced Virgo detectors and new detectors coming online in Japan and India, neutron star mergers will be detected at a higher rate in the future, starting with the O3 observing run which will begin in early 2019. The detection of electromagnetic emission from these mergers provides vital information about merger parameters and allows independent measurement of the Hubble constant. The Australian Square Kilometre Array Pathfinder is expected to become fully operational in early 2019, and its 30 deg2 field of view will enable us to rapidly survey large areas of sky. In this work we explore prospects for detecting both prompt and long-term radio emission from neutron star mergers with Australian Square Kilometre Array Pathfinder and determine an observing strategy that optimises the use of telescope time. We investigate different strategies to tile the sky with telescope pointings in order to detect radio counterparts with limited observing time, using 475 simulated gravitational wave events. Our results show a significant improvement in observing efficiency when compared with a naïve strategy of covering the entire localisation above some confidence threshold, even when achieving the same total probability covered.

We present a catalogue of 668 major metre-wavelength radio events. The data was collected from dynamic spectra (taken at Dapto, N.S.W. until 1966 and at Culgoora, N.S.W. thereafter) by means of a radio spectrograph, which records the intensity of radio emission as a function of both frequency and time. A description of the major types of metre-wavelength phenomena can be found in Wild et al. (1963), Kundu (1965), Wild and Smerd (1972) and Kruger (1979), and details of the radio spectrograph in Sheridan (1963, 1967) and Labrum (1972).

The distribution of mass in a spiral galaxy is usually inferred from its rotation curve. The curve is most conveniently measured using part of its extreme population I such as HI or HII. This has a low velocity dispersion so that the observed tangential motion is in the absence of non-circular motions (van der Kruit and Allen 1978; Bosma 1981a, b) close to the circular velocity required to balance the gravitational force. The main difficulty is that for a detailed interpretation of the rotation curve one has to make assumptions on some general properties of the mass distribution, even though it is true that one can estimate the total mass within the last measured point to an accuracy of about a factor two. That of axial symmetry is only the simplest of assumptions. On the basis of the light distribution with a usually prominent disk component one often assumes that the mass distribution is also basically highly flattened.

Reverse drift pairs were first described by Roberts (1958) and later by Ellis (1969) and de la Nòe and Moller-Pedersen (1971). Figure 1 shows a 10-min section of the spectrograph record and the corresponding section of the polarimeter record. The figure contains several reverse drift pairs and illustrates the main features of RDPs, namely: (1) frequency drift rate of about 4 MHz s-1 (i.e. a factor of ~50 faster than Type lis and a factor of ~2 slower than type Ills); (2) drift to higher frequencies (i.e. opposite to that of Type II and III bursts, hence the name ‘reverse’); and (3) an apparent ‘echo’ of the burst some 1 to 2 s later to form a pair. On 1979 February 17/18 a noise storm consisting of Type 1 bursts, Type III bursts and an underlying continuum was observed with the Culgoora spectropolarimeter, spectrograph, and radioheliograph. During this noise storm, the spectrograph record showed several hundred RDP bursts, and about fifty FDPs. Here we report new results on the polarization-of drift pair bursts, present further data on RDP positional and frequency characteristics, and then comment on existing theories concerning RDPs.

Since the start of high-resolution observations with the radioheliograph at the Culgoora Solar Observatory it has been noted that some bursts which occur from separate active regions could be physically correlated. It was suggested that the time delay between the correlated bursts is of the order of seconds, and that fast electrons provide the trigger. Wild found that shortly before a large flare weak bursts, stronelv polarized in the same sense, appeared simultaneously in different sources after a quiet period and he discussed the phenomenon in the light of flare mechanisms.

Compact symmetric objects are considered the young counterparts of large doubles according to advance speeds measured or inferred from spectral ageing. Here we present a simple power law model for the CSO/FR II evolution based on the study of sources with well defined hot spots. The luminosity of the hot spots is estimated under minimum energy conditions. The advance of the source is considered to proceed in ram pressure equilibrium with the ambient medium. Finally, we also assume that the jets feeding the hot spots are relativistic and have a time dependent power. Comparison with observational data points to an interpretation of the CSO–FR II evolution in terms of decreasing jet power with time.

A number of solar filaments/prominences demonstrate failed eruptions, when a filament at first suddenly starts to ascend and then decelerates and stops at some greater height in the corona. The mechanism of the termination of eruptions is not clear yet. One of the confining forces able to stop the eruption is the gravity force. Using a simple model of a partial current-carrying torus loop anchored to the photosphere and photospheric magnetic field measurements as the boundary condition for the potential magnetic field extrapolation into the corona, we estimated masses of 15 eruptive filaments. The values of the filament mass show rather wide distribution in the range of $4\times10^{15}$ – $270\times10^{16}$ g. Masses of the most of filaments, laying in the middle of the range, are in accordance with estimations made earlier on the basis of spectroscopic and white-light observations.

In late 1998 the International Gemini Project Office identified a need for a low cost, near-infrared spectrograph to be commissioned on the Gemini South telescope on the shortest possible timescale. In response, the Research School of Astronomy and Astrophysics of the Australian National University proposed to design, construct, and commission a near-infrared, integral-field spectrograph on Gemini. The science drivers and novel design of the Near-infrared Integral-Field Spectrograph (NIFS) are described in this paper. NIFS will achieve significant economies in cost and schedule in several ways:

• By addressing targeted science with high efficiency. NIFS will primarily target velocity measurements in galaxies to study the demographics of black holes in galactic nuclei and the evolution of structural properties in high redshift galaxies. However, NIFS will also be applied to a wide range of general astronomical topics, but these will not dictate the instrument design.

• By adopting a largely fixed-format design. A 3·2″ × 3·2″ ‘stair-case’ integral field unit (IFU) will feed a near-infrared spectrograph with four fixed-angle gratings mounted on a single grating wheel. A single, fixed-format camera will form the spectral image on a 2048 × 2048 Rockwell HgCdTe HAWAII-2 array. Two-pixel spectral resolving powers of ∼5400 will be achieved with complete wavelength coverage in each of the J, H, and K photometric bands through 32 optimally sampled 0·1″ wide slitlets. The velocity resolution of ∼55 km s−1 will be sufficient to achieve the targeted science objectives, and will allow software rejection of OH airglow lines.

• By packaging the NIFS instrument within a duplicate of the Near-Infrared Imager (NIRI) cryostat. The NIRI cryostat, On-Instrument Wavefront Sensor (OIWFS), detector focusing mechanism, control system, and EPICS software will all be duplicated with only minimal change. Construction of the duplicate NIRI cryostat, OIWFS, and control system will be done by the University of Hawaii.

Recent observations using several different telescopes and sky surveys showed patterns of asymmetry in the distribution of galaxies by their spin directions as observed from Earth. These studies were done with data imaged from the Northern hemisphere, showing excellent agreement between different telescopes and different analysis methods. Here, data from the DESI Legacy Survey was used. The initial dataset contains $\sim\!2.2\times 10^7$ galaxy images, reduced to $\sim\!8.1\times 10^5$ galaxies annotated by their spin direction using a symmetric algorithm. That makes it not just the first analysis of its kind in which the majority of the galaxies are in the Southern hemisphere, but also by far the largest dataset used for this purpose to date. The results show strong agreement between opposite parts of the sky, such that the asymmetry in one part of the sky is similar to the inverse asymmetry in the corresponding part of the sky in the opposite hemisphere. Fitting the distribution of galaxy spin directions to cosine dependence shows a dipole axis with probability of 4.66 $\sigma$ . Interestingly, the location of the most likely axis is within close proximity to the CMB Cold Spot. The profile of the distribution is nearly identical to the asymmetry profile of the distribution identified in Pan-STARRS, and it is within 1 $\sigma$ difference from the distribution profile in SDSS and HST. All four telescopes show similar large-scale profile of asymmetry.

The fraction (fesc) of ionizing photons that escape their host galaxy and so are able to ionize hydrogen in the intergalactic medium is a critical parameter in studies of the reionization era. In this paper we constrain fesc at high redshift by modelling the observed Lyα transmission. Using an N-body simulation of the cosmic web, we first model an ionizing background due to star-bursting galaxies. We then extract an ensemble of mock absorption spectra from the simulation and compute the mean transmission. We adjust the free parameter, fesc in our model of the ionizing background to reproduce the observed transmission. We find that fesc increases with the minimum galaxy mass considered to contribute to the ionizing background, and that at high redshift fesc must be greater than 5% irrespective of galaxy mass. Based on our numerical results we calibrate a semi-analytic model which shows that the ionizing background observed at z ∼ 5.5–6 implies a sufficient number of ionizing photons to have reionized the Universe by z ∼ 6. However, if the minimum mass for star-formation were ≳109 M⊙, the ionizing background would be over-produced at z ≲ 5. In summary, our results indicate that the Universe was reionized by low mass galaxies.

The three-body problem is famously chaotic, with no closed-form analytical solutions. However, hierarchical systems of three or more bodies can be stable over indefinite timescales. A system is considered hierarchical if the bodies can be divided into separate two-body orbits with distinct time and length scales, such that one orbit is only mildly affected by the gravitation of the other bodies. Previous work has mapped the stability of such systems at varying resolutions over a limited range of parameters, and attempts have been made to derive analytic and semi-analytic stability boundary fits to explain the observed phenomena. Certain regimes are understood relatively well. However, there are large regions of the parameter space which remain unmapped, and for which the stability boundary is poorly understood. We present a comprehensive numerical study of the stability boundary of hierarchical triples over a range of initial parameters. Specifically, we consider the mass ratio of the inner binary to the outer third body ( $q_\mathrm{out}$ ), mutual inclination (i), initial mean anomaly and eccentricity of both the inner and outer binaries ( $e_\mathrm{in}$ and $e_\mathrm{out}$ respectively). We fit the dependence of the stability boundary on $q_\mathrm{ out}$ as a threshold on the ratio of the inner binary’s semi-major axis to the outer binary’s pericentre separation $a_\mathrm{in}/R_\mathrm{p, out} \leq 10^{-0.6 + 0.04q_\mathrm{out}}q_\mathrm{out}^{0.32+0.1q_\mathrm{out}}$ for coplanar prograde systems. We develop an additional factor to account for mutual inclination. The resulting fit predicts the stability of $10^4$ orbits randomly initialised close to the stability boundary with $87.7\%$ accuracy.

This programme was undertaken because the preliminary observations of Beta Centauri with the Narrabri stellar interferometer (Hanbury Brown, Davis, Allen, and Rome) show that the correlation received is not consistent with that expected from a single star. The Lick Catalogue of Radial Velocities states that β Cen is a Bl II star. The Narrabri results are consistent with several models; in particular, it may be a double star with components of similar brightness, or it may have a very luminous, extended atmosphere or shell surrounding it. The latter possibility is perhaps unlikely on the spectroscopic evidence, as there are neither emission nor sharp absorption components in the spectral lines.

It is well known that the satellite systems of the major planets Jupiter, Saturn and Uranus share many of the same regular features that can be seen in the planetary system of the Sun. The inner satellite orbits are nearly circular and lie in the plane defined by the axis of rotation of the central body. Again the distances Rn of the regular satellites, numbered inwards to the centre n = 0, 1, 2, …, form a nearly geometric sequence

Rn/Rn + 1 ≌ constant,

similar to the Titius-Bode law of planetary distances. These facts suggest that the same cosmogonic process must have been responsible for the origin of both types of systems.

Data from the Solar Maximum Mission satellite suggests that there is a 0.1 percent variation in solar luminosity over the 11-year solar cycle with maximum output corresponding to maximum sunspot number. Tree ring chronologies can be utilized as proxy data to compile a record of the magnitude of past solar variability. Spectral analysis of tree ring series compiled from a site in Tasmania has established, among others, significant periodicities of about 90 and 11 years. The application of band pass filter techniques shows that the 11-year cycle present in some tree ring series correlates with the Zurich sunspot numbers over the period from AD1700, the extent of accurate sunspot records, with a time lag of about three years.

The far-ultraviolet magnitudes of late-F, G and early-K dwarfs with (B − V) ⩾ 0.50 as measured by the GALEX satellite are shown to correlate with soft X-ray luminosity. This result indicates that line and continuum emission from stellar active regions make significant contributions to the flux in the GALEX FUV band for late-F, G and K dwarfs. By contrast, detection of a correlation between FUV brightness and soft X-ray luminosity among early-F dwarfs requires subtraction of the photospheric component from the FUV flux. The range in (B − V) among F and G dwarfs over which a correlation between uncorrected FUV magnitude and X-ray luminosity is detected coincides with the range in colour over which coronal and chromospheric emission correlates with stellar rotation.

Spin patterns of spiral galaxies can be broadly separated into galaxies with clockwise (Z-wise) patterns and galaxies with counterclockwise (S-wise) spin patterns. While the differences between these patterns are visually noticeable, they are a matter of the perspective of the observer, and therefore in a sufficiently large universe no other differences are expected between galaxies with Z-wise and S-wise patterns. Here, large datasets of spiral galaxies separated by their spin patterns are used to show that spiral galaxies with Z-wise spin patterns are photometrically different from spiral galaxies with S-wise patterns. That asymmetry changes based on the direction of observation, such that the observed asymmetry in one hemisphere is aligned with the inverse observed asymmetry in the opposite hemisphere. The results are consistent across different sky surveys (SDSS and PanSTARRS) and analysis methods. The proximity of the most probable asymmetry axis to the galactic pole suggests that the asymmetry might be driven by relativistic beaming. Annotated data from SDSS and PanSTARRS are publicly available.

High-resolution spectroscopy and spectropolarimetry have been undertaken at the Anglo-Australian Telescope in order to identify suitable targets for magnetic studies of young Sun-like stars, for the proxy study of early solar evolution. This study involved the investigation of some variable late F- / early G-type Sun-like stars originally identified by the Hipparcos mission. Of the 38 stars observed for this study, HIP 31021, HIP 64732, HIP 73780 were found to be spectroscopic binary stars, while HIP 19072, HIP 67651 and HIP 75636 are also likely to be binaries and HIP 33111 could even be a triple system. Magnetic fields were detected on a number of the survey stars: HIP 21632, HIP 43720, HIP 48770, HIP 62517, HIP 71933, HIP 77144, HIP 89829, HIP 90899 and HIP 105388, making these stars good candidates for follow-up Zeeman Doppler imaging studies.