Many early-type stars are in systems; some of them have been indicated as putative high-energy emitters. The radiation would be produced at the region where two stellar winds collide. Compelling evidence of such emission was found only for the colliding-wind binary (CWB) Eta Car, which was associated to a GeV source. Very recently, the closest CWB, WR 11, was proposed as a counterpart of a 6σ emission excess, measured with the Fermi LAT satellite. We sought evidence to support or reject the hypothesis that WR 11 is responsible of the gamma-ray excess. Archive radio interferometric data at 1.4 and 2.5 GHz taken with the Australia Telescope Compact Array along 16 dates were reduced. The sizes of the field-of-view at 2.5 GHz and of the central region of the Fermi LAT excess are alike. We analysed the emission of the WR 11 field, characterised the radio sources detected and derived their spectral indices, to investigate their nature. Eight sources with fluxes above 10 mJy were detected at both frequencies. All but one (WR 11) showed negative spectral indices. Four of them were identified with known objects, including WR 11. A fifth source, labeled here S6, is a promising candidate to produce gamma-ray emission, besides the CWB WR 11.

Bipolar structures are discernible in three categories of solar radio emission: the slowly varying component (S-component), microwave bursts and metre-wavelength type I storms. Piddington and Minnett, discussing the S-component, showed that when coupling between the magneto-ionic modes along the ray path is ignored the emission from a regular dipolar field should have two specific polarization properties. These properties (see Figure 1) are that both feet of the bipolar structure should be similarly polarized, i.e. both left-hand (LH) or both right-hand (RH), and that this handedness should reverse on central meridian passage (CMP). (Reversal of the handedness at CMP had been suggested earlier by Martyn.) These arguments should apply also to microwave bursts and to type I storms.

We discuss a generalisation of the synchrotron bubble model which has been applied to short-lived radio transients which can peak and decay over just a few days. The assumptions of the simple model imply that when the flux is increasing with time, it must also be an increasing function of frequency. Observations of two recent radio transients, Nova Muscae 1991 and the Galactic Centre Transient, include the first data showing such a rising phase, and in both cases the radio flux was a decreasing function of frequency during the observed rising phases. Thus the simple synchrotron bubble model is inadequate, at least for these events. A fundamental feature of the simple model is the assumption that the process accelerating the radiating electrons ceases before the radio emission can escape. We relax this assumption by including an injection of electrons, with a constant energy spectrum, into the synchrotron bubble.

The theory of coronal structure and of the associated angular momentum transport by magneto-thermo-centrifugal winds is reviewed, with reference to recent observations of rapidly rotating late-type stars. In particular, the combined optical and X-ray studies of AB Doradus are consistent with the predicted picture of a hot, magnetically-controlled ‘dead zone’ in near corotation with the star, and of cooler wind-emitting regions (analogues of the solar coronal holes). The standard theory predicts a rate of angular momentum transport that depends on the extent of the wind zone, the relative importance of thermal and centrifugal driving, and the variation of the dynamo-built surface field with rotation. For stars like the Sun, with approximately one tenth of the mass in the convective envelope, detailed comparison of the theory with the observed rotations of stars in clusters of different ages is sensitive to the strength of the coupling between the envelope and the radiative core, and is constrained by helioseismological limitations on rotational shear within the present-day Sun. An inferred strong braking during the early epochs may hint at a non-standard braking model, with the Maxwell stresses dominant far from as well as near the stellar surface.

Star formation is believed to occur in interstellar clouds consisting of both gas and grains. Under the gravitational influence of such a cloud the constituent dust grains sediment toward the centre, and both calculations and implications of this sedimentation have been published by many authors (McCrea and Williams 1965; Horedt 1973, 1976; Prentice 1976; Krautschneider 1977; Flannery and Krook 1978; and others). Two main results from these calculations warrant our attention. Firstly, the timescale for appreciable sedimentation Ts ≃ 107 -108 years, which is consistent with age estimates of many clouds (Harrison 1978, Blitz and Shu 1980). Secondly, the sedimentation proceeds more rapidly for larger grains. This leads to an increase of mean grain size toward the centre of the cloud.

We present results of infrared continuum observations of the circumstellar disk surrounding the complex M78-SSV63.

Recent spectroscopic investigations of OB stars by Walborn (1970,1971a) have revealed the existence of OB stars with anomalous nitrogen and carbon spectra. In particular, two groups of stars were identified — those with strong nitrogen features and accompanying weak carbon-oxygen blends (called ON stars), and those with weak nitrogen features and strong carbon features (called OC stars). These groups bear a striking resemblance to the WN, WC dichotomy exhibited by the Wolf Rayet stars and is suggestive that a common process may be responsible for both phenomena.

Spectrum analysis of video tapes of the Jupiter S bursts in the frequency range 8-24 MHz with a frequency resolution of 2 kHz and a time resolution of 0.5 ms has shown that many of the bursts with instantaneous bandwidths less than about 10 kHz and which appear single with lower resolution, are actually double in the frequency-time plane. The frequency interval between the two components varied from 6 kHz at 9 MHz to 10.5 kHz at 23 MHz, and the corresponding time intervals from 1.3 msec to 0.6 ms.

The Parkes radio telescope was commissioned in 1961, with an anticipated operational life of 15 years. Twentyfive years later the telescope has been refurbished with the aim of extending its life yet another decade or two. A major undertaking has been the complete replacement of the drive and control System. This presentation outlines the main features of the new System and its effect on the observing facilities offered at the observatory.

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.

Detailed observations of the importance 2 flare of 9 June 1968, 00h25m U.T., were made at Culgoora in both its Hα and 80 MHz radio emissions, and the event should provide an opportunity for careful study. In this paper a description is given of the radio spectral observations (25-200 MHz) taken at the same site. These observations were among the first to be taken with a newly constructed spectrograph.

This paper gives a short description and interpretation of some solar magneto-hydrodynamical and plasma phenomena, based mainly on work by the writer and his collaborators (for an extended review see Kaplan et al. 1974).

The magnetic field is considered as the main factor responsible for a number of manifestations of solar activity. At the photospheric level active regions are displayed as plages, i.e., bright areas, seen near the limb. This means that the temperature gradient in plages is smaller than in the undisturbed photosphere. The decrease in gradient is a result of an increase of convective transport of energy.

‘History is Bunk’ said Henry Ford. He was exaggerating but it is well recognized that the connection between history and truth is tenuous. Even very recent history dependent on human memory is notoriously unreliable despite the intention of the historian to tell the truth.

In radio astronomy we are fortunate in having a dedicated historian-astronomer by the name of Woody Sullivan who has spent years in interviewing and reinterviewing astronomers to find out the real facts about the early years of the subject. Because of Sullivan’s work (e.g. Sullivan 1988) and because so many of my former colleagues have written histories of the period I felt very doubtful about adding my piece to the saga when asked to do so. However, I did accept the invitation to do so after I had read a statement about radio astronomy written by our usually very well informed Minister for Science, Barry Jones (Jones 1987). This statement which I shall quote later is an example of what we may call popular history.

The magnetic field and orbital period distributions of AM Herculis binaries are investigated. Our study shows that (i) there is a significant lack of very-high-field magnetic white dwarfs in binaries when compared with isolated white dwarfs, and (ii) the difference between the period distributions of AM Herculis binaries and other cataclysmic variable subclasses is statistically significant. These results imply that the evolution and the birth of AM Herculis binaries are different from those of other cataclysmic variables.

Analysis of surface and underground detector data from Mawson and Hobart for the period 1982 to 1988 has revealed a number of episodes of enhanced diurnal variation lasting more than 5 days. A preliminary study of these enhancements shows that variations in the rigidity spectrum and in the upper limiting rigidity must be present to explain the phenomenon.