We describe an ultra-wide-bandwidth, low-frequency receiver recently installed on the Parkes radio telescope. The receiver system provides continuous frequency coverage from 704 to 4032 MHz. For much of the band ( ${\sim}60\%$ ), the system temperature is approximately 22 K and the receiver system remains in a linear regime even in the presence of strong mobile phone transmissions. We discuss the scientific and technical aspects of the new receiver, including its astronomical objectives, as well as the feed, receiver, digitiser, and signal processor design. We describe the pipeline routines that form the archive-ready data products and how those data files can be accessed from the archives. The system performance is quantified, including the system noise and linearity, beam shape, antenna efficiency, polarisation calibration, and timing stability.

Multi-decade observing campaigns of the globular clusters 47 Tucanae and M15 have led to an outstanding number of discoveries. Here, we report on the latest results of the long-term observations of the pulsars in these two clusters. For most of the pulsars in 47 Tucanae we have measured, among other things, their higher-order spin period derivatives, which have in turn provided stringent constraints on the physical parameters of the cluster, such as its distance and gravitational potential. For M15, we have studied the relativistic spin precession effect in PSR B2127+11C. We have used full-Stokes observations to model the precession effect, and to constrain the system geometry. We find that the visible beam of the pulsar is swiftly moving away from our line of sight and may very soon become undetectable. On the other hand, we expect to see the opposite emission beam sometime between 2041 and 2053.

PSR B1828–11 is a young pulsar once thought to be undergoing free precession and recently found instead to be switching magnetospheric states in tandem with spin-down changes. Here we show the two extreme states of the mode-changing found for this pulsar and comment briefly on its interpretation.

The first known pulsar glitch was discovered in the Vela pulsar at both Parkes and Goldstone in March 1969. Since then the number of known glitches has grown enormously, with more than 520 glitches now known in more than 180 pulsars. Details of glitch parameters and post-glitch recoveries are described and some implications for the physics of neutron stars are discussed.

A reassessment of the taxonomic relationships of North American gigantopterids is presented in light of an examination of large populations of specimens housed in the US National Museum of Natural History. Variations in venation and subtle aspects of leaf shape facilitate refined understanding of the relationships and diversity of the North American gigantopterid species leading to an improved understanding of the taxonomic and biogeographic relationships of this group, which are found most abundantly in western equatorial Pangea and Cathaysia. Current literature suggests that there are eight North American genera, however, this study has revealed a morphological overlap of several previously defined genera, leading to the conclusion that Gigantopteridium encompasses the species previously treated as Cathaysiopteris yochelsonii as well as a new species, Gigantopteridium utebaturianum. The transfer of C. yochelsonii to Gigantopteridium yochelsonii suggests that Cathaysiopteris may represent a genus endemic to Cathaysia, limiting the biogeographical connection between the regions to Zeilleropteris, Gigantopteridium, Euparyphoselis, and Gigantonoclea.

The prompt radio emission associated with SN 1987A appeared and disappeared within the space of a few days. The next radio emission is expected as the high velocity ejecta expand into the circumstellar material. The evidence from the timing of the initial UV-flash is that this stage may occur shortly. We have therefore begun to monitor the field around SNR 1987A at high sensitivity with the Australia Telescope Compact Array. At λ6cm, an upper limit to the radio emission of 180μJy has been obtained. Continued observations are planned.

Pulsars are unique astronomical objects in that their emission is in the form of a periodic pulse train. For most pulsars the pulse duty cycle is small, only a few per cent of the period. The shapes and intensities of individual pulses are in general quite variable. This is illustrated in Figure 1 which shows a series of individual pulses from PSR 1133 + 16. Despite this variation in shape of individual pulses, it is found that the mean or integrated pulse profile obtained by adding many pulses synchronously with the period is in most cases stable in shape.

Observations of galactic HII regions in the longitude range 280° to 300° have recently been made at the OH-line frequencies 1612.231, 1665.402 and 1667.358 MHz using the Parkes radio telescope. Strong emission was observed at 1612 and 1665 MHz from a source near the regions of Hα emission RCW 48 and RCW 49 (Rodgers, Campbell and Whiteoak).

Over 600 pulsars are now known, almost all of which lie in our Galaxy. Most pulsars have periods between 0 · 1 and a few seconds, but a very important sub-class, the ‘millisecond’ pulsars, have much shorter periods. Millisecond pulsars are often in a binary orbit with another star, suggesting that their short periods are a result of accreting mass from the companion star. They are also extraordinarily good clocks, with a stability comparable to that of the best atomic clocks. This combination of extreme period stability and binary motion has led to some very important results, including the first observational evidence for gravitational radiation and the first evidence for extra-solar planetary systems. It is probable that pulsars will be used to define the long-term standard of terrestrial time. A search of the southern sky using the Parkes radio telescope has found several millisecond pulsars which will make an important contribution to these precision-timing programs.

Molonglo Observatory has played an important role in pulsar astronomy from shortly after the initial discovery announcement in 1968 to the present. Its major contribution has been in the area of searches for new pulsars – for most of the 17-year period more than half of the known pulsars were Molonglo discoveries. The history of pulsar astronomy at Molonglo is reviewed and a brief account of current observation programs is given.

Time variations in both the NGC 6334 and Orion OH sources have been reported by the Berkeley group. The variations in NGC 6334 have been partially confirmed by the group at the Lincoln Laboratory, who show that the variations are confined to the southern source, NGC 6334B. These latter authors find variable components at —6.6 and —7.9 km/s at 1665 MHz and at —8.9 km/s at 1667 MHz. Both features at 1665 MHz appear to vary, both up and down, with time; during 1966 October the characteristic rise time was nine days or less. The Berkeley results show that the linear polarization was constant during a two-week period in 1965 October. The Lincoln Laboratory results from 1966 October to 1967 June show that both the degree and sense of circular polarization remain constant as the three features vary with time.

A total of 18 radio sources selected on the basis of steep low-frequency radio spectra have been searched for the presence of millisecond pulsars using the Molonglo Observatory synthesis telescope. The search covered pulsar periods down to 2 ms with a limiting sensitivity of approximately 10 mJy. No pulsars were detected.

Pulse arrival time measurements allow the determination of accurate pulsar periods, period derivatives and, provided the data span is at least one year, precise pulsar positions. If observations are frequent and reasonably regular, irregularities in the period can also be investigated. To minimize the effect of possible variations in dispersion measure, it is important that these observations be made at a relatively high frequency, preferably above 1 GHz. To eliminate pulse shape variations due to variable ionospheric Faradayrotation, the pulse total intensity or one of the circular polarizations must be recorded.

During 1968 we have found at Parkes several types of emission in the lines of the 18 cm quadruplet of the ground-state OH molecule. This note describes a strong source of 1612 MHz emission near galactic longitude 331°.

OH emission was originally detected in the vicinity of HII regions, and a search of a large number of HII regions showed that about a third had associated OH emission. This type of emission is usually strongest at 1665 MHz, and is also seen at 1667 MHz and weakly on one of the satellite lines.

The proposal made to ASTEC for an Australian systhesis telescope (AST) is for a high-sensitivity, high-resolution synthesis array to be located at the Australian National Radio Astronomy Observatory, Parkes, and used in conjunction with the existing 64-m antenna at that site as a national facility (Wellington 1976). During the past 18 months a design study group consisting of representatives from the Australian National University, University of Sydney, University of Tasmania and CSIRO has been investigating the design of such an array. This paper reports on one aspect of this design, the array configuration.

During the Cretaceous and Paleogene, the Indian subcontinent was isolated as it migrated north from the east coast of Africa to collide with Asia. As it passed over the Reunion hotspot in the late Maastrichtian–early Danian, a series of lava flows extruded, known as the Deccan Traps. Also during this interval, there was a major mass-extinction event at the Cretaceous–Paleogene boundary, punctuated by a meteorite impact at Chicxulub, Mexico. What were the biological implications of these changes in paleogeography and the extensive volcanism in terms of biodiversity, evolution, and biogeography? By combining chronostratigraphic, paleosol, and paleobotanical data, an understanding of how the ecosystems and climates changed and the relative contributions of the Chicxulub impact, Deccan Traps volcanism, and paleogeographic isolation can be gained. Understanding relative ages of paleobotanical localities is crucial to determining floristic changes, and is challenging because different methods (e.g., magnetostratigraphy, radiometric dating, vertebrate and microfossil biostratigraphy) sometimes give conflicting answers, or have not been done for paleobotanical localities. Climatic data can be obtained quantitatively by studying paleosol geochemistry, as well as qualitatively by examining functional traits and nearest living relatives of fossil plants. An additional challenge is revising macrofossil data, which includes some confidently identified taxa and others with uncertain affinities. This is important for understanding ecosystem composition both spatially and temporally, as well as the biogeographic implications of an isolated India.