An estimate of the amount of ionizing radiation available in a supernova explosion falls far short of the amount needed in the standard model of the Gum nebula. The only possibility left is radiation from the pulsar.

Polarization and total power at 5000 MHz and 2700 MHz have been obtained for 30 supernova remnants (SNR) using the 64-m radio telescope at Parkes. This large sample includes a range of SNR from the young bright objects (such as Kepler's SNR) through the old faint sources such as MSH 14-63. Among the old remnants, the individual SNR have very varied properties, but several general conclusions emerge from our study. (1) In many cases, the polarization of the galactic background is as strong as that of the SNR and can vary significantly over the angular extent of the SNR. (2) The Faraday rotation is generally small and varies quite uniformly across the source. (3) The magnetic field patterns, although associated with the SNR, do not show any particularly characteristic pattern or relations to the total-power structure of the source.

Preliminary maps of the brightness distributions of 11 supernova remnants are presented. The sources, with diameters ≲10′, were observed at 160 MHz with resolution better than 2′. Ten of the supernova remnants are significantly resolved, and at least six show evidence of a shell-like structure. For those sources where high-frequency maps are available with comparable resolution the brightness distributions are generally very similar.

A rotational synthesis map of Cas A was obtained at 160 MHz with a resolution of 2 × 3′.

Continuum observations of IC 443 were made at 21 cm with a resolution of 23″×59″. The appearance in the radio continuum is very similar to the optical appearance. Since the radio emission is nonthermal, this requires a mechanism that can enhance the synchrotron volume emissivity within thermal filaments, which emit strong optical radiation. We suggest compression of gas and magnetic fields in a shock.

Tycho's remnant has been observed both at 21 cm (resolution 24″ × 27″) and at 6 cm (resolution 7″ × 8″). Most of the fine scale structure is resolved. The similarity at the two wavelengths indicates a remarkable constancy in the spectral index of features down to a scale of 20″.

By using the Maryland-Green Bank Galactic 21-cm Line Survey, a series of equal-velocity contour diagrams has been constructed for the regions of the extended sources W51 and W44. The non-thermal component of W51 has no absorption features above 53 km s-1, but its thermal components have clear absorption features up to much higher velocities. From this fact, the association of the thermal and nonthermal components of W51 is rejected. Absorption features toward W44 cannot be seen above 50 km s-1. Kinematic distances to the nonthermal component of W51 and to W44 are 4.4 kpc and 3.5 kpc, respectively. From peculiar brightness distributions in the equal-velocity contour diagrams I conclude that a dense Hicloud, as well as clouds of OH and H2CO, is associated with W44.

With the refinement of the estimates of electron density in the Galaxy it is clear that pulsars have z distances away from the galactic plane of a few hundred parsec. There is now a very strong indication that young pulsars lie at small z distances, suggesting that pulsars originate in a small z population and are given velocities of about 100 km s-1 at birth.

Estimates of the masses and energies of the supernova explosions that resulted in the Cygnus Loop and similar remnants are revised downward on the basis of recent soft X-ray observations.

Thirty optically visible stellar sources have been observed in the radio continuum: four red dwarf flare stars, three novae, two red supergiants, eight binary systems, and 13 related peculiar objects. The observations of red dwarfs, novae, and supergiants are briefly reviewed. Their emission seems reasonably well understood. Binary systems such as Algol show erratic flaring; consistent explanations have not yet been given. The related peculiar objects, such as V1016 Cyg and MWC 349, are even less well understood. Some of them may have just arrived on the main sequence; others may be planetary nebulae in an early stage of formation.

Data are presented for Cygnus X-1, Cygnus X-3, and Scorpius X-1 from radio to X-ray wavelengths. The evidence for Cygnus X-1's being a black hole is now quite convincing. New data for Cygnus X-3 show the presence of X-ray activity at the time of the giant radio outburst. The data for Scorpius X-1 show a close correlation between the X-ray and optical behavior, but coverage was not sufficiently complete to fully assess the relationship (if any) between the X-ray and optical emission and the radio emission.

The variation in flux density obtained at 10522 MHz for Bursts 2, 3, and 4 is compared with that obtained by others at frequencies down to 365 MHz. The bursts appear to have a quasi-periodic modulation with a period of 3–4 h, which is different from the 4.8-h periodicity observed at X-ray and infrared wavelengths. The modulation is attributed to a fluctuation in the size of the expanding cloud of particles produced by either an instability in the atmosphere of Cygnus X-3 or by a built-in instability in the cloud itself.

The 2.2 µm flux from the infrared counterpart of Cygnus X-3 has been found to vary in phase with the X-ray flux with a 4.8 h period. The infrared observations imply a radius ~ 1 R⊙ for the X-ray object and do not favor models involving a compact object such as a neutron star or a black hole.

165 planetary nebulae south of +27° declination have been observed with the Parkes 64 m telescope. These nebulae were chosen to include most of those for which Hβ flux densities are available. Radio positions and flux densities (generally with probable errors of only a few millijanskies) obtained from the survey must represent the most reliable and homogeneous radio data currently available for the class of object. The data have been used to obtain distances and optical extinctions for these nebulae.

A short report is presented on the aperture synthesis radio observations of planetary nebulae performed by Terzian et al. (1974). Examples of radio maps at 8085 MHz are shown with angular resolutions of the order of 2″ to 3″.

A small percentage of infrared stars, selected on the basis of their IR brightness at 2.2 µm and their redness (I–K colour index), show 18 cm OH emission, and some exhibit 1.35 cm H2O emission; further investigations identify some of these objects as M-type supergiants and the remainder as M-type giant long-period variable stars.

For the strongest 1612 MHz OH emitters, long-baseline interferometry shows that the emission arises from a large number of small-diameter features distributed over a much larger, approximately elliptical region corresponding to a circumstellar cloud. Models for the geometry of the emitting regions are discussed.

The OH characteristics with respect to the ratios of line intensities for different transitions and the velocity structure are distinctive, not being found in other types of OH source; consequently a large number of new OH emitters can be recognized as probably IR/OH objects despite the absence of IR or optical data; the precise classification of these sources is considered together with their relevance in understanding the identified sources.

Anomalous OH and H2O microwave emission is a common occurrence in circumstellar shells surrounding cool oxygen-rich M supergiants and Mira variables. Infrared spectra have shown that the atmospheric conditions in these stars are such that the concentration of OH molecules is a maximum. For those with H20 microwave emission, strong H20 1.9 μm absorption is present.

There exists a growing number of typical OH/IR sources discovered by radio surveys, for which no associated IR object has yet been found. Preliminary results of TV photography to discover IR counterparts are shown.

Several interesting correlations have been defined between the IR colour, period and amplitude of infrared variability, and the velocity separation of the OH emission peaks. The relationship of these to pulsationally driven mass loss and the observed characteristics of circumstellar dust shells is investigated.

The maser emission from OH/IR and H20 / I R sources is believed to be pumped by IR radiation. Combined studies of the variability of OH and H20 emission and the IR continuum of the Mira sources confirm that IR pumping is probably the dominant mechanism, although the data do not appear to favour any specific pump scheme. The OH masers are at least partially saturated; the degree of saturation of the H20 masers is unclear.

A pilot survey was made to study the feasibility of using radio observations of OH/IR stars to investigate the galactic distribution and kinematics of these presumably intermediate-population objects. Seven new sources were found, four near the center, two near l = 30°, and one at l = 128°.

IR observations of the region within 0°.5 of Sgr A are discussed. The total IR luminosity is 150 × 106 L⊙. Most of it is stellar radiation, absorbed by low temperature dust and reradiated in the IR. There is no unique interpretation for the highly structured infrared core. It may comprise compact infrared sources like those in some Hn regions, or the structure may simply result from the dust distribution. Nonthermal radiation is also feasible, but a tradeoff between source luminosity and extinction is possible and prevents a final decision on this question.

This review discusses unsuccessful searches for electromagnetic bursts accompanying gravitational events observed to come from the galactic center, radio observations of continuum emission and recombination lines from the region of the galactic center.

The Molonglo radio telescope has been used to map the galactic centre region with a resolution of 2.9′. Although similar to microwave maps of comparable resolution, there are differences. In particular, the source G1.05-0.1 is not visible at microwaves, and the source G0.1-0.0 is not visible at 408 MHz. The flux values of all the other sources around Sgr A confirm that they are thermal and that the sources G0.7−0.0, G0.5 − 0.0, and G0.2−0.0 are optically thick.

A more extensive galactic background survey with the cross shows the existence of a peak in the background emission with a brightness temperature of about 500 K at the galactic centre. This is probably the nonthermal source observed at 85 MHz. The higher-resolution observations of this map show the narrower, hotter region which appears on the microwave map and which surrounds Sgr A. This has a brightness temperature of 2100 K, which cannot be accounted for by a simple thermal spectrum extrapolated from microwaves.