This paper discusses the spatial distribution of M supergiant stars in the Galaxy using infrared data from IRAS.

Pulsars display a complicated pattern of amplitude variations. The scale of variations range from months through hours to sub-milliseconds. The purpose of this note is to present polarization data for CP 1919 and intensity distribution data for PSR 0833—45 which are relevant to pulse-to-pulse variations and the variation over periods of hours respectively.

Since its discovery by Haro (1952) the star H1-36 has been catalogued as a planetary nebula despite its extremely high-excitation emission-line spectrum (e.g. [Fe VII], [Ne V]) and its imposing, variable infrared excess. Because its optical spectrum resembled those of many symbiotic stars, I have persistently classified H1-36 as such. A meaningful definition of a symbiotic star would necessarily include both the high-excitation emission-line spectrum and the presence of a cool (usually M-type or Mira) giant.

We present results of VLBI monitoring observations of the blazars detected by ground-based TeV gamma-ray telescopes. Preliminary results have shown that the apparent speeds of the parsec-scale jet features in these sources are predominantly subluminal, and significantly slower than those in the GeV-peaked (EGRET) gamma-ray blazars. Here we add results from additional sources and additional epochs that increase the statistical significance of this comparison. These slower speeds may indicate rapid deceleration of the jets in TeV blazars between the TeV gamma-ray emitting scales and VLBI scales.

Observations have been made, using the Epping 4-m radio telescope, of emission from the J = 1-0 transition of CO (115 GHz) towards the Southern Coalsack. The half-power beam-width was 2′.7 arc and the radial velocity resolution was 0.07 km s−1. The line was found to be distributed with varying intensity over an area of 63′ × 36′ arc. The mean radial velocity was −5.8 km s−1 and mean half-intensity linewidth 1.18 km s-1. A typical line temperature was 8 K with maxima exceeding 12 K. The results suggest a stable dark cloud region with no significant evidence of systematic motions.

We use high-resolution n-body/SPH simulations to study the hydrodynamical interaction between the Large Magellanic Cloud and the hot halo of the Milky Way. We investigate whether the ram-pressure acting on the gaseous disk of the satellite can explain the peculiarities observed in the Hi distribution and the location of the recent star formation activity.

A theory of linear acceleration emission, with possible application to pulsars, is developed. The equation of motion for a relativistic charged particle accelerated in the field of a longitudinal wave is solved to first order in the electric potential and used to derive the first order current. The power emitted and the absorption coefficient are calculated and the conditions under which masing can occur are discussed.

In solar physics a need exists for filters which have very narrow passbands, ~0.01 nm or less. While Lyot-Öhman birefringent filters have been used particularly for investigations at the Hα line, the limited availability of the raw materials, especially calcite, have usually restricted these filters to passbands of ~ 0.025 nm or more. A possible alternative type of filter consists of a number of Fabry-Perot interferometers mounted one behind the other.

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.

Theoretical models of high-mass star formation lie between two extreme scenarios. At one extreme, all the mass comes from an initially gravitationally bound core. At the other extreme, the majority of the mass comes from cluster scale gas, which lies far outside the initial core boundary. One way to unambiguously show high-mass stars can assemble their gas through the former route would be to find a high-mass star forming in isolation. Making use of recently available CORNISH and ATLASGAL Galactic plane survey data, we develop sample selection criteria to try and find such an object. From an initial list of approximately 200 sources, we identify the high-mass star-forming region G13.384 + 0.064 as the most promising candidate. The region contains a strong radio continuum source, that is powered by an early B-type star. The bolometric luminosity, derived from infrared measurements, is consistent with this. However, sub-millimetre continuum emission, measured in ATLASGAL, as well as dense gas tracers, such as HCO+(3–2) and N2H+(3–2) indicate that there is less than ~ 100 M⊙ of material surrounding this star. We conclude that this region is indeed a promising candidate for a high-mass star forming in isolation.

We have used a sample of 263 Parkes half-Jansky flat-spectrum radio sources to measure the spatial correlation function of radio galaxies and radio-loud quasars on scales up to 1000 h−1 Mpc. We do not detect any clustering in the sample. If any undetected clustering is described by a power-law spatial correlation function [ξ(r) = (r/r0)−1·8], we can rule out clustering with scales r0 ≥ 50 h−1 Mpc at the 99·9% confidence level. We have also used the sample to test for the ‘possible’ large concentration of quasars in the direction of the microwave background dipole found by Shaver (1987). There is no evidence for such a concentration in our data and we show that the earlier result was probably biased by the use of non-uniform image classifications.

It is the usual practice during continuum radio observations at Parkes to observe ‘pointing sources’ concurrently with the program objects.

Traditional HI surveys of optically selected elliptical galaxies are time-consuming, and have a low detection rate. The forthcoming Parkes HI multibeam survey offers the exciting possibility of surveying more than 10,000 nearby elliptical galaxies for HI. I argue that this is likely to result in the detection of a large population of small, HI-rich elliptical galaxies which have not previously been studied in any systematic way.

The Edinburgh-Cape Bright QSO Survey is a very small sub-set of the Edinburgh Cape Blue Object Survey, which is a major survey to discover blue stellar objects brighter than B~18 in the southern sky. It will cover an area of sky of 10,000 square degrees with |b|>30 and dec <0. The blue stellar objects are selected by automatic techniques from U and B pairs of UK Schmidt Telescope plates scanned with the COSMOS measuring machine. Follow-up photometry and spectroscopy is being obtained with the SAAO telescopes to classify the types of objects brighter than B=16.5, with some of the more stubborn objects being subjected to AAO service spectroscopy. Some preliminary results for the 6% QSO minority are presented in this paper and comparison is made with the Palomar-Green QSO Survey in the north, which we find to be at least a factor of two incomplete.

The absorption counterpart of curvature emission is reexamined based on the Landau-Lifshitz approach. Early derivations led to the conclusion that maser emission is not possible, but these early derivations neglected a drift effect which was first discussed by Zheleznyakov and Shaposhnikov. When the drift effect is included, the derivation implies that curvature maser emission is possible. It is shown that for maser emission to be possible, the Lorentz factor needs to satisfy γ ≳ 103 for radius of curvature of the magnetic field lines RB ≈ 106 to 109cm and frequency ω ≈ 107 to 1011 s−1. Possible application to pulsars is discussed.

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.

Swinburne Astronomy Online (SAO) is an online graduate program in astronomy intended particularly for amateur astronomers, science communicators and educators. SAO emphasises the development of conceptual understanding and good communication skills in astronomy. The use of asynchronous discussion forums is a central feature of SAO. These 'online tutorials' were introduced partly with the intention of breaking down the isolation of distance education, but mainly to provide a venue where students could deepen their conceptual understanding of astronomy and hone their science communication skills while discussing course material with other students and instructors.

In this project aspects of the use of discussion forums in SAO were investigated, with comparisons made between average marks awarded for discussion forum contributions and those awarded for other assessment tasks, plus analysis of the rate at which students post to the forums, and an investigation of whether gender makes a significant difference to participation rate and assessment results. Responses by students to surveys that probe their ability to express themselves and communicate with classmates in this online form of distance education are discussed. Finally, possible implications for the use of discussion forums as a supplement to face-to-face teaching in astronomy are explored.

The dominant process in the evolution of spiral galaxies like our own is clearly the formation of new stars, and the leading optical indicator of this is Hα emission. Considering the tremendous importance of star formation and its variation within and between galaxies, it is surprising just how little survey work has been carried out at Hα. After the successful development of Tech Pan films for deep photographic imaging with the UKST, and given the particular sensitivity of Tech Pan at wavelengths near Hα, it was natural to consider the possibilities for a narrowband Hα imaging survey of large angular extent. This idea quickly developed into a full-blown survey of the whole of the Southern Milky Way, of the Magellanic Clouds, and of selected extragalactic regions of interest such as that around the Virgo Cluster. This special issue is devoted to the discussion of the details of making and using this survey.

We have performed a uniform and unbiased imaging survey of the Large Magellanic Cloud, using the IRAC and MIPS instruments on board the Spitzer Space Telescope. This Spitzer survey of the Large Magellanic Cloud is surveying the agents of a galaxy's evolution (SAGE), the interstellar medium and stars. The SAGE data are nonproprietary and the team has been creating catalogs and improved images for use by the astronomical community. This paper highlights some of the initial results being published by the SAGE team covering the topics of evolved stars and their mass-loss return to the ISM, young stellar objects and the properties of the ISM dust.

The recent discovery of two distant satellites of Uranus suggests that there could be similar bodies orbiting Neptune. Previous surveys for distant satellites of Neptune have had relatively bright magnitude limits (BJ ≃ 20·5) and would have missed satellites with magnitudes and colours similar to the two recently discovered Uranian satellites (R ~ 20·4 and R ~ 21·9). We have searched for satellites of Neptune to a limiting magnitude of R ~ 21 in a 0·1□° region centred on the planet. This search is up to ~ 2 magnitudes deeper than the previous wide field search for distant satellites by the UK Schmidt Telescope. Nereid was easily recovered by the search and no large variations of its magnitude were detected.