At a previous meeting of the Society I well remember Paul Wild saying, in a humorous vein of course, that until recently he had always thought that an H-R diagram was a plot of H against R. It occurs to me that the same kind of vagueness, although perhaps not to the same degree, might be present with astronomers not directly concerned with the theory of stellar atmospheres in regard to ‘L.T.E.’ and ‘Non-L.T.E.’ analysis of spectral lines. In the present paper, I would like to point out some of the important features of non-L.T.E. analysis, to indicate how the basic theory may be developed, and to show what effect this has on the theoretically produced absorption lines. I will make particular reference to the solar atmosphere and here we take the ‘model atmosphere’ approach where all the physical parameters such as gas pressure, electron pressure, temperature etc., are all specified as functions of optical depth.

About 13% of bright galaxies are ellipticals (21% SO, 64% Spiral and Im, 2% IO and peculiar). Their obvious features are the smooth luminosity distribution and the near absence of the bright blue stars, HII regions and dust that appear in spiral systems; there is probably very little star formation going on at present in E galaxies. I plan to discuss some of the dynamical and physical properties of these systems; although many of them are known radio sources, I will not be able to discuss their radio properties.

In this preliminary study the first two-dimensional pictures showing detailed features of the quiet Sun and weak but moderately stable structure at metre wavelengths are presented. The observations were made at 80 MHz with the Culgoora radioheliograph.

In this paper 80 MHz heliograph observations are described of a remarkable solar outburst on 1969 March 30 initiated by a flare on the invisible hemisphere of the Sun. The event raises several questions of theoretical interest, in particular the implication that the magnetohydrodynamic waves responsible for certain type II bursts must travel along curved paths.

Type II solar bursts characteristically drift slowly from high to low frequencies at a rate of about 0.1 MHz/s, appear only at frequencies lower than 250 MHz, and frequently have harmonic structure, i.e. there are identifiable spectral features within the fundamental which are duplicated at twice the frequency. Thus it is clear that at least in some cases, true harmonic radiation is involved; the source region emits frequencies f and 2f simultaneously.

Prior to the advent of the Culgoora 80 MHz radioheliograph position measurements on type II solar bursts were restricted to those made with one-dimensional interferometers. These measurements yielded conflicting evidence on the apparent positions of fundamental and harmonic emission observed at a given frequency; different observers reported the fundamental to be closer to and further from the centre of the Sun than the harmonic. Here we report on two-dimensional observations at 80 MHz made on both fundamental and harmonic emission of a type II event that occurred on 1969 March 2. The observations are shown to be consistent with the hypothesis that the emission is produced as the result of a disturbance moving out from the site of a flare and forming a shock front within an overlying coronal streamer. Both fundamental and harmonic are explained by ‘forward’ emission from the shock front. Observations of the harmonic emission at 158 MHz are also consistent with this model.

Travelling disturbances in the solar corona with velocities ~103 km/s manifest themselves at radio frequencies by two distinctive phenomena—the type II burst, the spectrum of which shows a slow frequency drift that corresponds to quasi-radial outward motion, and the moving type IV burst, for which positional observations show transverse motion directly. A close relation between the two phenomena has long been suspected, and each type has separately been ascribed to a shock wave disturbance. In this paper we summarize three events recorded by the Culgoora radioheliograph and spectograph (two in the course of publication and one unpublished) in each of which a type II and a moving type IV burst can be consistently attributed to the effects of a common shock wave.

For a number of years the occurrence of isolated groups of apparently related type III bursts has been recognized as a common feature of the dynamic spectral records of solar radio emission at metre wavelengths. Interferometer observations supported the simple hypothesis that bursts of a group were usually located in the same position. In this note we report 80 MHz observations made with the Culgoora radioheliograph which show that although the sources of the bursts in a group tend to overlap one another, their centroids may show marked scatter and that their distribution tends to be along narrow lanes across the solar disk. Since the 80 MHz sources occur at heights (≳ 0.6 R⊙) near or above the plasma level, these lanes doubtless reflect some structural feature of the outer corona.

The U-burst, first identified by Maxwell and Swarup and Haddock, is a type of solar radio event lasting ~ 10 s in which the frequency of the emission at first drifts rapidly downwards, then increases again. On the dynamic spectrum record the burst has the appearance of an inverted letter U.

Regions of the interplanetary medium currently inaccessible to space vehicles may conveniently be studied using the radio scattering properties of the interplanetary plasma. These effects may give rise to angular broadening of radio sources sufficiently close to the Sun, or to amplitude scintillation of sources of small angular size.

Recent observations of the radio-frequency flux spectrum of Jupiter in the frequency range 80-10 000 MHz suggest that the synchrotron component is not independent of frequency as has been generally accepted. Rather, the flux decreases at frequencies below 300 MHz and above 3000 MHz. In this paper we show that extensions and variations of the well-known dipolar model for this emission can account for the modified spectrum.

During the interval May 1968 to March 1969 the 80 MHz radioheliograph at Culgoora has been used in a detailed study of the intensity variations in the pulsars CP 0834, 0950, 1133 and 1919. Some preliminary results for CP 1133 and 1919 have already been reported.

While monitoring Barnard’s star in Ophiuchus for flare activity in August 1969, we accidentally recorded two bright flares on an early type star, 66 Oph. Apart from Andrews’ unconfirmed observation of a flare on a B8 star and Eggen’s report of a flare on the β Cephei Variable, (BO) HD 199 140, no other record of an early type flare star is known to the authors.

In the past a number of analytical solutions have been found to the differential equation for small radial adiabatic oscillations of stars, with the aid of a series expansion of the form leading to a two-term recurrence relation.

The aim of this work is to investigate certain assumptions that have been made in calculating line profiles and equivalent widths of neutral helium lines in early type stars. The effect of electron scattering on the continuum flux is investigated and a curve of growth analysis carried out to study this effect. The theories involved in calculating the line absorption coefficient are also investigated.

In an early paper Sterne investigated the pulsational properties of three stellar models with specified density distributions. He assumed a solution for the relative amplitude of the displacement to be of the form and on substitution into Eddington’s equation for small radial adiabatic oscillations of a star obtained a two-term recurrence relation to solve for the an in the case of each model.

A powerful approach to the understanding of any group of stars is the study of any companion stars which can be shown to be physically connected. But RR Lyrae variables, in common with other members of Population II are deficient in physical pairs. Baize’s catalogue of variables with companions contains only one: CSV 1795 = ADS 9354 A. As far as can be determined no period or light curve has been published for this star and it remains doubtful whether it is an RR Lyrae variable.

Much of the information regarding the nature of solid particles in interstellar space has been gained through the study of the line-of-sight extinction of starlight and the polarization of starlight by these particles. Study of the optical properties of these particles can be extended through consideration of the scattering of stellar radiation in reflection nebulae. This type of approach requires the adoption of models for the star-nebula system, and the grain type to be considered. These models are then used in a theory which describes the scattering of light by an ensemble of small particles, as applied to dust nebulae. Results are thus obtained for the colour of the nebula as a function of distance from the illuminating star. These results can then be compared with the corresponding results of experimental broad-band photometry.

An extensive survey of HI absorption in the spectra of discrete radio sources has been in progress for the past three years at the Parkes radio observatory. One part of the survey comprising sources along the galactic plane north of declination —50° has recently been completed. In this communication we discuss some conclusions concerning the distances of 10 sources drawn from a preliminary analysis of the data.

From an assessment of recent high-resolution galactic radio surveys, in the continuum and in the H109oc recombination line, the author has detected or confirmed over 90 non-thermal sources, most likely all supernova remnants.1 The distances to each of these objects have also been estimated, from an empirical surface-brightness linear-size relationship derived from 15 remnants whose distances are known from either a comparison of the radial velocities and proper motions of filaments in the nebula, neutral hydrogen absorption measurements, or association of the remnant with an object of known distance. In this note we wish to remark on the galactic distribution of supernova remnants and the possible association of these objects with pulsars and X-ray sources.