The proposal that the complex spectral line changes seen in the large amplitude β Cephei variable BW Vul resulted from a shock effect, driven by an underlying radial pulsation, was first made by Odgers (1955). Stamford and Watson (1978) examined some suitable atmospheric models for this star, which were driven by a hard subphotospheric piston under an isothermal assumption. These models displayed strong shock development and had some encouraging similarities with the BW Vul phenomenon. However, particularly because of the use of a hard piston, they were not very physically realistic. Here we discuss the results of a more sophisticated approach to this modelling problem. This modelling problem is of specific current importance because Odell’s (1981) recent observations of a variable polarization in BW Vul have renewed the debate over possible nonradial pulsations in this star. Since nonlinear effects are clearly substantial in BW Vul, it is evident that the implications of these on the observed spectral line changes should be carefully examined on a radial pulsation hypothesis, before turning to the complexities of nonlinear nonradial profile modelling.

Spectrophotometric optical fluxes of SN 1987A have been measured at high accuracy with the 61cm telescope equipped with a rapid spectrum scanner. This highly homogeneous data set covers the wavelength range 3200-8700Å at 10Å resolution. Selected wavelength regions, e.g. around Hα, have also been measured at 3Å resolution. The Hα line shows an undisturbed P Cygni-type profile until March 15, superimposed by variable fine-structure thereafter, developing within a few days into a blue-shifted, peak-like flux excess and a red-shifted flux deficiency. This fine-structure is intrinsic to Hα. Similar fine-structure is also observed in Na I-D, in Paschen-α and possibly in Hβ. We discuss our observations in terms of the ‘mystery spot’, and of models involving a jet and interactions with surrounding pre-existing material, and we propose density inhomogeneities, or occupation number deficits due to NLTE effects, within the inner regions of the envelope as origin.

During the last solar cycle a number of observations of solar radio emissions were made in a wide frequency range from which an enormous amount of information has been obtained. However the results obtained so far are limited by rather poor angular resolution. Observations with much higher resolution (of the order of 1′ arc) have been required for further studies of solar radio emissions. At the present stage such observations have proceeded in the microwave range; also the radioheliograph at 80 MHz has just started at the Culgoora Observatory. At the Tokyo Astronomical Observatory a high-resolution study of radio bursts in the metre-wave range has been planned since 1960, and the construction of a new compound interferometer operating at 160.3 MHz was started in April 1967 at a new site, Nobeyama. This site, located about 150 km north-west of Tokyo, is surrounded by mountains and quite free from man-made interference. We shall give a brief description of this equipment; details will be published later.

The Perth Astronomy Research Group (PARG), consisting of members from Curtin University of Technology, Perth Observatory and the University of Western Australia, is in the process of developing an automated supernova search system, using the 61-cm Lowell-Perth reflector, a CCD camera and an 80386-based computer for image analysis. Computer control of the telescope and dome, a liquid-nitrogen-cooled CCD camera, and modified VISTA image analysis software will be completed in late 1990, allowing initial semi-automatic searching of external galaxies, together with CCD photometry of flare stars and newly discovered supernovae. Full-scale automation will be introduced subsequently, in collaboration with the Berkeley group. This paper describes the project, and reports on its current status.

New observations of the Magellanic Stream were made in December 1976 with the 64-m radio telescope at the Parkes Observatory of CSIRO. The ridges of H I emission of the Stream were traced from near its tip at ℓ = 90°, b = -40° to the Magellanic Clouds. This was the first time that the total length of the Stream was observed with the one system (only possible from the southern hemisphere) and with high spatial (15’ of arc) and velocity (4 km s-1) resolution. The results of this survey are presented in Figures 1 and 2 and the main features are listed below.

The binary flare star AT Mic has been observed with the VLA (5 GHz and 1.5 GHz) and, nearly simultaneously, with the MOST (0.843 GHz). There appears to be a slowly varying component of the radio intensity, with a flux density greater at 0.843 GHz than at higher frequencies. It is suggested that above 1 GHz the emission is possibly produced by incoherent gryosynchrotron radiation, whereas below 1 GHz a coherent mechanism predominates.

Since the start of high-resolution observations with the radioheliograph at the Culgoora Solar Observatory it has been noted that some bursts which occur from separate active regions could be physically correlated. It was suggested that the time delay between the correlated bursts is of the order of seconds, and that fast electrons provide the trigger. Wild found that shortly before a large flare weak bursts, stronelv polarized in the same sense, appeared simultaneously in different sources after a quiet period and he discussed the phenomenon in the light of flare mechanisms.

Observations of five cepheids in Crux are described and annual epochs of maxima presented. The O–C diagram of S Crucis shows changes between two alternative periods. The observing method appears suited to sites with only a limited number of hours available.

In 1994 December we installed a Celestron CG11 Telescope at Belgrano Base (previously called Belgrano II) for site seeing measurements and variable star observations. We describe the project, logistics, installation and working environment. We present the first quantitative observations of astronomical seeing conditions at Belgrano Base.

A complete orbital light-curve of V2051 Oph in the IR H band is presented, together with a second eclipse in the J band. Simultaneous Rc band data were obtained. Eclipse depths in Rc, J and H are 1.8 mag, 1.0 mag and 0.8 mag respectively. No evidence for ellipsoidal variations due to the secondary was seen and constraints on the secondary are discussed.

The astrophysical literature contains many discussions on exactly which changes in a star’s structure are responsible for the extremely large radii found after core hydrogen exhaustion. Different authors favour different mechanisms. Unfortunately none of the proposals are easily verified nor are they easily disproven. In this paper we examine the suggestion that it is the increased central mass concentration (i.e., the growth of the hydrogen exhausted core) which is the primary agent responsible for envelope growth.

This year the School of Electrical Engineering began observations with the new Fleurs compound interferometer. This instrument operates at 21 cm and has a fan-beam response 35″ arc wide in an east-west direction.

The most recent helium abundance determinations in main sequence B stars are those of Hardrop and Scholtz, Kodaira and Scholtz, Norris, and Leckrone. Their results indicate that it is possible to assign a helium abundance which is characteristic of all B stars. Norris and Leckrone worked with a number of B stars ranging from B0 to B9, and both have assigned a characteristic helium abundance to the B stars. Norris derived a value, A = 0.088 ± 0.012, and Leckrone a value of A = 0.106 ± 0.01, where A is the abundance of helium relative to hydrogen by number.

The purpose of this paper is to obtain an expression for the reflecting properties of a semi-infinite, plane parallel, isothermal atmosphere of scattering factor λ. The absorption and scattering of the incident radiation is assumed to be entirely due to transitions in two-level atoms, and the absorption and emission profiles are given by <f>(y), y being frequency from line centre in Doppler units.

Observations at a number of frequencies indicate that for at least two pulsars the average pulse shape has a slow but quite definite frequency dependence. Figure 1 shows average pulse shapes for CP 1919, CP 0950 and CP 1133. With the exception of those at 408 MHz these results were obtained at Parkes. The 408 MHz pulse shapes were obtained at Jodrell Bank by Lyne and Rickett. Circumstances of the observations are listed in Table I. Linearly polarized feeds were used at all frequencies.

A number of New Zealand universities offer astronomy courses at different undergraduate levels. The courses are taught in Physics or Mathematics Departments. Some are only sub-courses within a physics major rather than a dedicated astronomy course. I will detail these and show material relating to the course content and some of the texts used. Postgraduate programs in astronomy are also offered, principally at the University of Canterbury but also at the University of Auckland and Victoria University of Wellington.

The complex consisting of the bright HII region M17 (G15.0-0.7) and its associated molecular cloud is well known as a region of active star formation which contains an abundance of many different molecules (see e.g. Lada 1976). For H2CO, observations of the 110 – 111 transition at 4.8 GHz towards the HII region show an intense narrow absorption feature with a radial velocity near + 24 km s−1 superimposed on weak absorption which extends to below +10 km s−1 (Whiteoak and Gardner 1970). According to Whiteoak and Gardner (1974) the latter consists of several features centred at the velocities of +4.7, + 10.4, + 17.9 and +20.3 km s−1. Lada and Chaisson (1975) mapped the absorption around M17 with a 6′ .5 arc beam and concluded that the broad component was associated with the obscuring dust cloud near the HII region while the narrow feature occurred in a foreground cloud. In this paper we present observations made with higher angular resolution and higher sensitivity; they define better the H2CO distribution and its relationship with the extended CO cloud near M17 (Elmegreen et al. 1979).

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.