Interesting observations have been made possible by the success of the acousto-optical radio spectrograph, a unique form of multi-channel filter type of spectral receiver whose channel outputs ian be sampled at high rates by a computer. Three spectrographs are available at the Division of Radiophysics. Two divide a 100 MHz spectral range into 512 channels and are normally dedicated to spectral-line work (Cole and Milne 1977) and solar work (Cole et al. 1978). The Parkes observations reported here use a more compact spectrograph, which gives increased performance — up to 270 MHz can be studied, divided into 256 frequency channels. The light deflector of this spectrograph was kindly supplied by Itek Corporation.

Lin and Hudson (1976) have recently analysed non-thermal processes in proton flares, using observations of a series of major events in August 1972. They concluded that the 10–100 keV electrons accelerated during the flash phase account for the bulk of the total energy of a large proton flare (about 1032 – 1033 ergs); that most protons are accelerated later than the 10 — 100 keV electrons; and that most energetic protons escape to the interplanetary medium. Their conclusions with regard to proton acceleration are supported firstly by the delay of the maximum of γ-ray emission by 3-5 minutes after the maximum of X-ray emission, and secondly by the satisfactory agreement between the 7-ray spectrum and the thin-target model of emission. The energetic protons contain a very small fraction of the total flare energy (of the order of 10-5).

Both radial and non-radial motions have been suggested at various stages to explain the observational peculiarities of the β Cephei variables. The non-radial possibility has been investigated most recently by Smith (1977) and Stamford and Watson (1977). We here examine the radial shock proposal by generating a series of isothermal radial shock models in suitable early B star atmospheres. Odgers (1955) has long advocated such a model in connection with the large amplitude variable BW Vul. The observations of Goldberg, Walker and Odgers (1976) clearly show a radial velocity ‘stillstand’ effect and line splitting in this star. We discuss our models in the context of these two phenomena.

The strategic value of infrared sensing has prompted military development — mostly in the USA — of detectors for 8-30 μm far more sensitive than any commercially available. In 1970-72 the Air Force Cambridge Research Laboratories conducted a rocket-borne survey of the sky N. of about -35° dec at 4,11 and 20 μm. Although this survey was initially classified, a small number of preliminary versions of it were distributed to selected infrared astronomers based at U.S. institutions.

Tananbaum et al. (1976) have recently added to the Uhuru catalogue 4U1608-52, a source varying by over an order of magnitude in a time span of some months. They identified the object with MXB1608-52, a highly variable X-ray source of flares and bursts. (Kaluzienski et al. 1976; Belian et al. 1976; Grindlay and Gursky 1976a, b; Li 1976). There have been a number of earlier X-ray observations of sources very close to 4U1608-52 (Cooke and Pounds 1971; Luyendyk et al. 1973; Thomas et al. 1975; Grindlay and Gursky 1976b; Ricker et al. 1976), and in this paper we propose the identification of these earlier sources with 4U1608-52. We thereby obtain additional spectral information and can now rule out a globular cluster as the optical counterpart of the object.

Solar flares for which protons of relativistic energies reach Earth are rare events compared with the number in which non-relativistic protons are produced. For instance, Shea and Smart (1978) have listed 139 proton events for the interval 1955-69 of which 17 were GLE’s (i.e. “ground level events” detected by the world network of cosmic ray neutron monitors). We have tentatively identified a further 11 GLE’s in the interval 1970-1977, of which 3 were in 1977 in the sunspot cycle which commenced about mid-1976 (cycle 21). Thus the average rate over the past two solar cycles has been a little over one per year.

The completion of the Uhuru (Forman et al. 1978) and Ariel V (Cooke et al. 1978) surveys of the sky for X-ray emission has resulted in many proposed identifications with individual galaxies and clusters of galaxies. The X-ray positions are not usually accurate enough to enable a positive identification to be made of the X-ray sources with optical or radio objects, and hence the identification is often based on statistical arguments — viz., the unexpected occurrence of unusual galaxies, radio sources or clusters of galaxies within or near the X-ray error boxes. There is usually no significant information available on the angular size of the X-ray emitter but in two or three cases (e.g. Perseus cluster, Coma cluster and Virgo cluster) the angular resolution is good enough to identify a broad component with dimensions approaching those of the whole cluster. This extended X-ray emission has been ascribed to either inverse Compton scattering of the 3° microwave background by relativistic electrons in the intra-cluster medium or to thermal-bremsstrahlung emission by an optically thin plasma at - 10s K.

In variable star work, the frequent observations of comparison stars during a night often clearly indicate the presence of either changes in extinction or changes of zero point of the photometric system, or both effects simultaneously. In a magnitude — air mass plot, the graph is not linear, but is usually a loop. These loops are well known to observers but so far very little has been published about this problem. Young’s (1974) chapters are perhaps the only exception.

The double-mode or beat Cepheids form a group of some 10 variables at the short period end of the classical Cepheid period range, which exhibit two (or three) simultaneous pulsations with remarkably constant period ratio (see Table I). If, as seems likely, the two periods (P0 and P1,) are to be identified with fundamental and first-overtone radial oscillations, linear pulsation theory may be used to yield a mass and a radius estimate for each beat Cepheid (Mbear and Rbeat) based on period observations alone. The masses so obtained may be compared with two other Cepheid mass estimates: the pulsation mass, Mpuls, is derived by the application of pulsation theory to one observed stellar period (usually P0) and a radius calculated from the stellar luminosity and temperature; the evolutionary mass, Mevol, is inferred from the stellar luminosity by the application of stellar evolution results (without mass loss) for Population I stars in the core helium-burning phase. If a Cepheid is a member of a cluster or association whose distance and reddening have been determined, the Cepheid luminosity and temperature may be obtained observationally, yielding Mpuls, and Mevol estimates directly. For other Cepheids, only indirect estimates may be made, based on the period-luminosity-colour relationship calibrated using the Cepheids with cluster membership.

It is now generally accepted that the remnants of supernovae (SNRs) are of two types, recognizable by their radio structure and spectral index. To date most of the radio sources identified as SNRs are of the easily identified shell type. These have spectral indices a of -0.5 ±0.2 and exhibit some degree of annular brightness distribution — the projection of the radio shell. The second type, e.g. the Crab Nebula, have filled structures and relatively flat (a = -0.1 ±0.1) spectral indices. The relatively strong radio polarization exhibited by some members of this class has led to their identification but generally they tend to be hidden amongst the HII regions in our galaxy.

Observations of Jupiter’s decametric radio burst have established that above 20 MHz more than 90% of the emission is elliptically polarized in the RH sense, but below this frequency the proportion of the LH polarization increases (Sherrill 1965) until at 10 MHz nearly 40% of the emission is LH polarized (Dowden 1963). The best time and frequency resolutions so far obtained when examining the polarization of the spectra of Jupiter’s bursts have been 10 ms and 50 kHz respectively (Gordon and Warwick 1967, Riihimaa 1975). To study the fine structure of Jupiter’s emission as observed by the linearly polarized Llanherne low frequency radio telescope (Ellis 1972), spectrum analysers with resolutions in the ranges 0.3 — 1 msec and 2–10 kHz have been used (Ellis 1973a, 1973b, 1974, 1975). A new telescope at Llanherne, which is capable of detecting the RH and LH circular components of incident radiation, is being used in conjunction with these analysers to yield information of the hyperfine polarization structure of Jupiter’s decametric radio emission. This paper is a preliminary report of this investigation.

The Fleurs Synthesis Telescope (FST) has been used to map a number of bright, southern galactic HII regions at 1415 MHz. Descriptions of the FST can be found in Christiansen (1973) and associated papers. For the observations reported here, both the east-west and the north-south arms of the cross were used resulting in beamshapes which are nearly circular with half-power widths of 50” arc. The maps have been “cleaned” using a standard process (Högbom 1974).

The radio source associated with Circinus X-1 has been observed several times at Molonglo since 1970 and some of these observations have already been reported (Whelan et al. 1977). In 1977 the source was again observed, this time for 17 consecutive days and during these observations the position and flux of the reference source 1505-56.9 were more precisely determined. A few sporadic observations have also been made in 1978. This note brings together the new observations and all the old measurements which have been corrected on the basis of the new data for 1505-56.9 Other observations have been made which were not calibrated against this source but these have not been included in this note since they are less well calibrated.

As part of an identification programme undertaken on the southern section of the Molonglo Deep Sky Survey of Radio Sources, the limiting magnitudes of some of the available ESO-B films and SRC-J films and plates in this area have been determined. The Molonglo Deep Sky Survey has been described by Robertson (1977). The southern section comprises a 45’ wide strip centred about declination -62° and stretching in an irregular fashion from 18h 25m to 00h 16m.

During the Skylab period from June 1973 to January 1974 approximately 1500 type III metre-wave radio bursts or burst groups were reported (Solar Geophysical Data Prompt Reports). The longitudinal distribution of these type III bursts closely resembles that of sunspots and of the coronal transients observed above 2 R⊙ by the white-light coronagraph on Skylab. White light ejection transients appear as large loop or blob-like structures which carry material outward from the Sun and rearrange the corona. In front of the main, bright structures there are weak enhancements of brightness, termed forerunners (Jackson and Hildner 1978; Jackson 1978). In this paper we enquire into whether or not type III bursts are in any way related to the onset of solar mass ejections indicated by coronal transients.

The fact that Jupiter’s inner magnetosphere is not axially symmetric was originally demonstrated by ground-based radio measurements. Departures from symmetry are evident in the pattern of bursts occurring at decametre wavelengths and also in the characteristics of the polarized synchrotron emission observed at decimetre wavelengths. Direct measurements of Jupiter’s magnetic field, made from the Pioneer space probes, also indicate departures from an axially symmetric configuration.