Report on the latest developments in the modelling of Solar granules and in particular, the influence of various viscosity laws on the theoretical predictions, such as the velocity field, intensity modulation, degree of overshooting into upper stable layers and so on.

A morphological comparison between radar meteor survey data obtained at Ottawa (Millman and McIntosh, 1964) from 1958 to 1962 and that obtained from Christchurch (Ellyett and Keay, 1963) in 1960-61, confirms that the Daytime Arietid, Delta Aquarid meteor shower association is the most prominent feature of the annual activity. The data from Canada and New Zealand are easily reconciled as far as this activity is concerned and also for the weaker Eta Aquarid shower which, having a radiant at zero declination, is equally prominent in both sets of data. Furthermore, the data from both hemispheres is consistent with a forty per cent increase in overall activity during the second half of the year.

We resolve a conflict in the literature concerning the effect of induced Compton scattering on the propagation of radio waves through the electron–positron wind surrounding a pulsar.

We have just completed the observational stage of a 2·4 GHz survey of the Southern Galactic Plane, using the Parkes radiotelescope, between 238° ≤ l ≤ 365° and with a latitude range of at least |b| ≤ 5° (beamwidth ~9 arcmin). The survey details both continuum emission and linear polarisation down to rms noises of approximately 12 and 4 mJy/beam respectively. It is the most sensitive survey to date of the southern plane at this frequency and should nicely complement the Effelsberg northern plane surveys in addition to the recent southern surveys such as the 843 MHz MOST survey and the 5 GHz PMN survey. The total-power maps are now completed, and reduction of the polarisation data is still in progress. In addition to compact HII regions and extragalactic sources, we are detecting on our total-power images a considerable amount of large-scale structure, and a significant number of new SNR candidates and spur-like features.

We present the results of an analysis of the spectra obtained for a sample of 27 Am stars. We find evidence for the presence of groups amongst these stars and argue that all Am stars exhibit a pseudo–luminosity effect.

Instruments were flown on the Pioneer 6 and 7 spacecraft during 1965-66 to study the degree of anisotropy of cosmic radiation in the energy range 7.5-90 Mev/nucleón. The instruments record the cosmic ray fluxes from each of four contiguous ‘quadrants’ of azimuthal rotation of the spacecraft, for each of three energy windows 7.5-45 Mev, 45-90 Mev, and 150-350 Mev for alpha particles and heavier nuclei. In addition, the counting rate of all particles of energy >7.5 Mev is recorded, thereby providing cosmic ray data of high statistical precision useful in the study of fast changes in the cosmic ray flux.

The recent intensive study of Comet Halley based on in situ measurements, observations carried out with rockets and satellites and supplemented with co-ordinated Earth based observations has not only confirmed pre-Halley results, but also has given new insight into the nature of the nucleus, dust, gas and the interaction of cometary plasma with the solar wind. These observations also have raised many new questions and problems. Several of these aspects will be discussed. For a better understanding of these problems, the planned future missions to comets will also be discussed.

One of the two main telescopes at Sydney Observatory is a computer-controlled 35.6-cm Celestron. It is used with a television-type system. There is an integrating CCD camera available as well as an ordinary TV camera for bright objects. The images from the cameras can be shown in the Observatory’s lecture room. They are first put through an image processor which allows constant enhancement, spatial filtering and the recording of images for use on cloudy nights. Preliminary results are encouraging, and show the value of the system, even in Sydney’s highly light-polluted sky.

This paper summarises Ginga X-ray observations of SN 1987 A.

Numerical simulations suggest that colliding molecular clouds induce gravitational collapse and may be responsible for star formation. We incorporate magnetic fields in these simulations and present preliminary results of an investigation of the influence of magnetic fields on star formation via this process.

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.

Savage et al. (1977) found that the radio source PKS 1448-232 coincided with a stellar object of about magnitude 16.4 having an ultraviolet excess. A low resolution spectrum obtained with the Anglo-Australian Telescope (AAT) confirmed this object as a QSO with zem = 2.22 and revealed many absorption lines short-ward of the La emission. Consequently this object was included in a programme of spectroscopy at intermediate resolution with the AAT to investigate QSO absorption lines. Savage et al. have given a finding chart with an optical position of 14h48m09s.3, −23°17′10″ (1950.0). The radio fluxes are 0.40 Jy at 2.7 GHz and 0.31 Jy at 5.0 GHz.

Our recent papers have been devoted to basic studies of diatomic and polyatomic molecules (Singh and Chaturvedi 1989 a,b,c,d; 1990a,b,c). A critical analysis of the 456 available references in literature has been made to select 135 polyatomic molecules, molecular ions and radicals containing from three to thirteen atoms of astrophysical significance. The results have been arranged in a text-cum-tabular form (Singh and Chaturvedi 1989 b,d). The compilation contains various information for each molecule, such as the spectral region, transition levels, and astrophysical objects where the respective molecules have been detected (say, comet, meteorite, Sun, planet, star, interstellar medium. Galaxy, etc.).

Observations of the composite radio source which includes the catalogued components 1209-52 and 1209-51 (Bolton et al. 1964) have been obtained at frequencies 629, 1410, and 2650 MHz with the 210-ft Parkes telescope. The observations at the highest frequency are shown in Figure 1. The isotherms of full-beam brightness temperature correspond to the single polarization direction shown within the circle representing the half-intensity beamwidth. The polarization vectors (unbroken lines) along the two ridges represent 15-25% linear polarization. The intrinsic angles of polarization, derived from the 1410 and 2650 MHz observations, are represented by the broken lines. They are perpendicular to the magnetic field if the radiation is synchrotron. The corresponding rotation measures (Gardner and Whiteoak 1963) range between +17 and +36 rad. m-2 along the eastern ridge, and between —14 and —4 on the western side.

This paper describes the Star Watch Program in Japan to monitor night-sky brightness.

During a recent balloon flight from Mildura, Australia, the region of the Galaxy between −10° < l II < +20°; −5° < b II< +5° was surveyed for high-energy X-rays of photon energy > 17 keV (λ < 0.7 Å) using an active collimation scintillation detector described elsewhere. The narrow opening angle of the telescope enables two sources to be resolved in this region of the sky. The position of one of these sources agrees well with the source GX3+1 observed at rocket wavelength by Bradt et al. while the other source is probably the same as that observed by Gursky et al. and designated GX−5.6. We present herein improved positional information for this latter source which hereafter will be designated GX354−5.

The polytropic stellar model with index n = 0 has a uniform density distribution throughout, and consequently its physical radius is essentially arbitrary because the surface density condition, ϱ = 0, is never satisfied. This surface anomaly, which is not associated with the other polytopic models for 0 < n ≤ 5, could be a constraining factor in certain astrophysical applications involving the n = 0 polytrope. For example, in some circumstances it may be appropriate to utilize the simple physical formulation of the model but on the other hand inappropriate to disregard any zero boundary requirements for the surface density. A sequence of new E-type (as defined below) composite analytical solutions to the Lane-Emden equation, based on the indices 0 and 1, has been developed which eliminates this physical indetermination. The associated polytropic models can be classified as essentially uniform density models. Specifically, they have a large central uniform density n = 0 zone matched, in a physically consistent way, to a small outer n = 1 zone which has a steep density gradient giving ϱ = 0, along with T = 0 and P = 0, at the radial distance corresponding to the first zero of the composite solution.

Guthnick and Prager (1929) were the discoverers of the variability of AH Virginis. Prager (1929) produced a photographic light curve the same year. Lause (1934, 1935, 1937) observed the system visually and improved the period as deduced by Prager. Further visual work on the system was done by Zessewitsch (1944). The first photoelectric observations came from Huruhata and Nakamura (1951), followed in 1952 by Kitamura, Tanabe and Nakamura (1957).

Lack of their data on ingress and egress at primary eclipse resulted in the mean curve showing a rounded bottom during minimum light. From this, an inclination of the system of 61° was derived by Kopal and Shapley (1956). Two years later, Kwee (1958) revealed primary minimum to be flat bottomed; the light remaining constant for some 40 minutes. This was confirmed by Binnendijk (1960), thus classifying AH Virginis as one of the few W UMa systems which display complete eclipses at an inclination likely to be closer to 90° then to 61°. Observations of the present study confirm constancy of light of 40 minutes duration during primary minimum. Assuming i = 90°, a new orbital solution was derived by Kitamura and Takahashi (1959) showing constant light for both minima. Binnendijk’s observation, however, showed a curved appearance at secondary minimum. The present observations indicate curved as well as flat secondary minima.

The reappearance of radio emission from SN 1987A is discussed. We propose a model involving synchrotron radiation from electrons which are accelerated when the expanding supernova shock wave runs into a density jump in the circumstellar material, and which then expand adiabatically.