An N-body code containing live stellar evolution through combination of the software packages nbody6 and stars is presented. Operational details of the two codes are outlined and the changes that have been made to combine them discussed. We have computed the evolution of clusters of 104 stars using the combined code and we compare the results with those obtained using nbody6 and the synthetic stellar evolution code sse. We find that, providing the physics package within stars is set up correctly to match the parameters of the models used to construct sse, the results are very similar. This provides a good indication that the new code is working well. We also demonstrate how this physics can be changed simply in the new code with convective overshooting as an example. Similar changes in sse would require considerable reworking of the model fits. We conclude by outlining proposed future development of the code to include more complete models of single stars and binary star systems.

We present colour transformations for the conversion of Wide-Field Survey Explorer W1, W2, and W3 magnitudes to the Johnson–Cousins BVIc, Sloan Digital Sky Survey gri, and Two Micron All Sky Survey JHKs photometric systems, for red clump (RC) stars. RC stars were selected from the Third Radial Velocity Experiment Data Release. The apparent magnitudes were collected by matching the coordinates of this sample with different photometric catalogues. The final sample (355 RC stars) was used to obtain metallicitydependent and free-of-metallicity transformations. These transformations combined with known absolute magnitudes at shorter wavelengths can be used in space density determinations for the Galactic (thin and thick) discs at distances larger than the ones evaluated with JHKs photometry alone, hence providing a powerful tool in the analysis of Galactic structure.

A knowledge of the on-ice seeing is a key requirement for planning future Antarctic observatories. In this paper we discuss the likely negative impact on seeing produced by the development of the deep winter surface temperature inversion (Ekman layer). The Automated Astronomical Site Testing Observatory (AASTO) will deploy, as one of its complement of site-testing instruments, an automated differential image motion monitor (DIMM) telescope designed to generate seeing data throughout the Antarctic winter. Here we describe the multi-aperture concept which has been developed for this mission, and touch upon some of the critical technological considerations associated with the low power budget and with the requirement of autonomous operation at very low temperature (–90°C).

We present photometric observations of six radio-loud quasars that were detected by the COMPTEL gamma-ray telescope. The data encompass seven wavebands in the optical and near infrared. After correction for Galactic extinction, we find a wide range in optical slopes. Two sources are as blue as optically-selected quasars, and are likely to be dominated by the accretion disc emission, while three others show colours consistent with a red synchrotron component. We discuss the properties of the COMPTEL sample of quasars, as well as the implications our observations have for multiwavelength modelling of gamma-ray quasars.

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.

We have recently confirmed the planetary nebula (PN) nature of PM 1–242, PM 1–318 and PM 1–322. Here we present high-resolution long-slit spectra of these three PNe in order to analyze their internal kinematics and to investigate their physical structure. PM 1–242 is a tilted ring and not an elliptical PN as suggested by direct images. The object is probably related to ring-like PNe and shows an unusual pointsymmetric brightness distribution in the ring. PM 1–318 is a pole-on elliptical PN, instead of a circular one as suggested by direct images. PM 1–322 is spatially unresolved and its spectrum shows large differences between the forbidden lines and Hα profiles, with the latter showing a double-peaked profile and relatively extended wings (FWZI ~325 km s−1). These properties are found in other PNe that are suspected to host a symbiotic central star.

This is a paper on young jet material in a frustratingly complex environment.

NGC 1052 has a compact, flat or GHz peaked spectrum radio nucleus consisting of bi-symmetric jets, oriented close to the plane of the sky. Many features on both sides move away at υapp ˜0.26 c (H0 = 65 km s−1 Mpc−1). VLBI at seven frequencies shows a wide range of spectral shapes and brightness temperatures; there is clearly free–free absorption, probably together with synchrotron self-absorption, on both sides of the core. The absorbing structure is likely to be geometrically thick and oriented roughly orthogonal to the jets, but it is patchy.

HI VLBI shows atomic gas in front of the approaching as well as the receding jet. There appear to be three velocity systems, at least two of which are local to the AGN environment. The ‘high velocity system’, 125–200 km s−1 redward of systemic, seems restricted to a shell 1–2 pc away from the core. Closer to the centre, this gas might be largely ionised; it could cause the free–free absorption.

WSRT spectroscopy shows 1667 and 1665 MHz OH absorption over a wide velocity range. OH and HI profile similarity suggests co-location of molecular and atomic ‘high velocity’ gas; the connection to H2O masing gas is unclear. Further, at ‘high velocity’ we detected the OH 1612 MHz satellite line in absorption and the 1720 MHz line in emission, with complementary strengths.

We report the discovery of a bright ( $g = 14.5$ mag (AB), $K = 11.9$ mag (Vega)) quasar at redshift $z=0.83$ — the optically brightest (unbeamed) quasar at $z>0.4$ . SMSS J114447.77-430859.3, at a Galactic latitude of $b=+18.1^{\circ}$ , was identified by its optical colours from the SkyMapper Southern Survey (SMSS) during a search for symbiotic binary stars. Optical and near-infrared spectroscopy reveals broad Mg ii, H $\unicode{x03B2}$ , H $\unicode{x03B1}$ , and Pa $\unicode{x03B2}$ emission lines, from which we measure a black hole mass of $\log_{10}\! (M_{\mathrm{BH}}/\mathrm{M}_{\odot}) = 9.4 \pm 0.5$ . With its high luminosity, $L_{\mathrm{bol}} = (4.7\pm1.0)\times10^{47}\,\mathrm{erg\,s}^{-1}$ or $M_{i}(z=2) = -29.74$ mag (AB), we estimate an Eddington ratio of $\approx1.4$ . As the most luminous quasar known over the last ${\sim}$ 9 Gyr of cosmic history, having a luminosity $8\times$ greater than 3C 273, the source offers a range of potential follow-up opportunities.

We present results from a spectral line survey of the young stellar object IRAS 17470-2853, undertaken to examine chemical changes during the evolution from hot molecular cores to ultracompact HII regions. Observations were carried out with the Mopra 22 m radio telescope in the frequency range from 86.1 to 92.1 GHz. A total of 21 lines from 9 molecules were detected. Except for CH3CN they are all simple molecules. We compare the results to the ultracompact HII region G34.3+0.15, where spectral line surveys in the frequency range 80–115 GHz and 330–360 GHz have been performed. While the molecular lines detected are similar, their widths and intensities are somewhat narrower and lower, respectively, in IRAS 17470-2853. The typical line width of ˜5 km s−1 indicates relatively quiet or quasi-thermal emission. On the other hand, a significant difference in TA* (HNC)/TA*(HCN) has been found: 0.8 for IRAS 17470-2853 compared to 2.6 for G34.3+0.15. The broad line width of SiO (υ=0, J=2–1), ˜9 km s−1, suggests that IRAS 17470-2853 is experiencing a shock generated by the embedded object. Column densities, or lower limits to them, are derived for observed molecules.

We report early results of an observational campaign targeted on a sample of compact steep spectrum sources selected from the FIRST survey which are significantly weaker than those investigated before. The selection criteria and procedure are given in detail. We present here an assortment of MERLIN and VLBI observations and make some general comments based on the morphologies of the sources presented.

Optically, the Zone of Avoidance (ZOA) can only be explored to within a few degrees of the Galactic Equator. This restriction does not apply to radio wavelengths where we are able to detect galaxies at great distances behind the Galactic Plane. Using the Parkes 21 cm multibeam instrument we have detected neutral hydrogen (HI) in 42 galaxies in the region of the Great Attractor. We have been able to identify nine galaxies and make positional associations with a further six from existing optical catalogues, which makes at least 60% of these galaxies new discoveries.

Large numbers of the many types of emission-line object that are found in the Magellanic Clouds were first identified through Hα surveys of one kind or another. This paper looks at what has been achieved through such surveys and considers how the planned UKST Hα/TechPan Survey can further this kind of work.

Correlations are identified between the strength of the λ10830 He I triplet line and the following tracers of stellar activity amongst FGK dwarfs with colours of (B − V) > 0.47: coronal soft X-ray emission, emission in the λ1549 C IV and λ1335 C II lines originating from the transition region, and Ca II H and K emission from the chromosphere. No such correlations are present amongst dwarfs with spectral type earlier than F6. In addition, G and K dwarfs with strong triplet lines show evidence of excess flux in the GALEX FUV band compared to weak-triplet-line dwarfs. The X-ray spectra of late-F, G, and K dwarfs with He I triplets stronger than 160 mÅ have greater values of the ROSAT hardness ratio HR1 than are typical of weak-triplet dwarfs in the same range of spectral type. In other words, dwarfs later than F7V with strong He I triplet lines tend towards harder 0.1–2.0 keV X-ray spectra than weak-triplet dwarfs, although values of HR1 ~ −0.2 to +0.1 can still be encountered amongst a minority of weak-He-triplet stars. As regards, FGK main sequence stars the observational data on the λ10830 triplet line remains sparse. Progress could be made through spectroscopy of high resolution for samples of hundreds of stars, selected on the basis of having other measures of chromospheric and coronal activity available.

The confined nature of the debris from the Sagittarius dwarf to a narrow trail on the sky has recently prompted the suggestion that the dark matter halo of our Galaxy should be nearly spherical (Ibata et al. 2001; Majewski et al. 2003). This would seem to be in strong contrast with predictions from cold dark matter (CDM) simulations, where dark halos are found to have typical density axis ratios of 0.6 to 0.8. Here I present numerical simulations of the evolution of a system like the Sagittarius dSph in a set of Galactic potentials with varying degrees of flattening. These simulations show that the Sagittarius streams discovered so far are too young dynamically to be sensitive to the shape of the dark halo of the Milky Way. The data presently available are entirely consistent with a Galactic dark matter halo that could either be oblate or prolate, with density axis ratios c/a that range from 0.6 to 1.6 within the region of the halo probed by the orbit of the Sagittarius dwarf.

Therecently discovered massive binary system Apep is the most powerful synchrotron emitter among the known Galactic colliding-wind binaries. This makes this particular system of great interest to investigate stellar winds and the non-thermal processes associated with their shocks. This source was detected at various radio bands, and in addition the wind-collision region was resolved by means of very-long baseline interferometric observations. We use a non-thermal emission model for colliding-wind binaries to derive physical properties of this system. The observed morphology in the resolved maps allows us to estimate the system projection angle on the sky to be $\psi \approx 85^\circ$ . The observed radio flux densities also allow us to characterise both the intrinsic synchrotron spectrum of the source and its modifications due to free–free absorption in the stellar winds at low frequencies; from this, we derive mass–loss rates of the stars of $\dot{M}_\mathrm{WN} \approx 4\times10^{-5}\;\mathrm{M}_\odot\,\mathrm{yr}^{-1}$ and $\dot{M}_\mathrm{WC} \approx 2.9\times10^{-5}\;\mathrm{M}_\odot\,\mathrm{yr}^{-1}$ . Finally, the broadband spectral energy distribution is calculated for different combinations of the remaining free parameters, namely the intensity of the magnetic field and the injected power in non-thermal particles. We show that the degeneracy of these two parameters can be solved with observations in the high-energy domain, most likely in the hard X-rays but also possibly in $\gamma$ -rays under favourable conditions.

This paper presents the results of a multiwavelength observational study of the active young F-type star HR 1817. The star was monitored at 4.80 and 8.64 GHz over 2 × 12 h allocations with the Australia Telescope Compact Array on 8 and 9 December, 2000. The Anglo-Australian Telescope was used for simultaneous optical spectropolarimetry during a 2 h period on 9 December.

The low levels of observed radio emission have characteristics that are similar to those seen in other active stars, and a gyrosynchrotron mechanism is proposed to explain them; this is supported by the relatively low fractions of circular polarisation measured in HR 1817.

Comparison of the emissions from 4.80 and 8.64 GHz shows a very strong cross-correlation peak, indicative of a common origin, although the shift of this peak indicates that 8.64 GHz variations tend to precede those at 4.80 GHz by, typically, ˜20 min.

The optical spectropolarimetry reveals polarisation signals characteristic of surface magnetic fields, with profile changes indicating a complex dynamo-type magnetic topology is present on the star. This result makes HR 1817 the star with the earliest spectral type on which dynamo magnetic fields have been detected directly up to now.

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

Star formation does not occur until the onset of gravitational collapse inside giant molecular clouds. However, the conditions that initiate cloud collapse and regulate the star formation process remain poorly understood. Local processes such as turbulence and magnetic fields can act to promote or prevent collapse. On larger scales, the galactic potential can also influence cloud stability and is traditionally assessed by the tidal and shear effects.

In this paper, we examine the stability of giant molecular clouds (GMCs) in the Large Magellanic Cloud (LMC) against shear and the galactic tide using CO data from the Magellanic Mopra Assessment (MAGMA) and rotation curve data from the literature. We calculate the tidal acceleration experienced by individual GMCs and determine the minimum cloud mass required for tidal stability. We also calculate the shear parameter, which is a measure of a cloud's susceptibility to disruption via shearing forces in the galactic disk. We examine whether there are correlations between the properties and star forming activity of GMCs and their stability against shear and tidal disruption.

We find that the GMCs are in approximate tidal balance in the LMC, and that shear is unlikely to affect their further evolution. GMCs with masses close to the minimal stable mass against tidal disruption are not unusual in terms of their mass, location, or CO brightness, but we note that GMCs with large velocity dispersion tend to be more sensitive to tidal instability. We also note that GMCs with smaller radii, which represent the majority of our sample, tend to more strongly resist tidal and shear disruption. Our results demonstrate that star formation in the LMC is not inhibited by to tidal or shear instability.

We describe the application of Peltier effect cooling to charge coupled device (CCD) detectors. We are developing this technique to produce a CCD camera which requires low maintenance, yet has sufficiently small dark-current for long exposure imaging. This camera will be used in an automated imaging telescope at Siding Spring Observatory. The design principles used to maximise cooling of the detector, and hence minimise dark-current, are discussed. A small dark-current can be obtained only if great care is taken to reduce or eliminate convective, conductive and radiative heating of the chip. In addition, a path of high thermal conductivity must be provided for the heat removed from the CCD. A recent laboratory test of our cooling system demonstrates that careful design can lead to sufficiently low CCD dark-current for many astronomical applications.

The Chatterton Astronomy Department of the University of Sydney is proposing the construction of a very high angular resolution stellar interferometer of major astronomical and international significance. Based on the prototype modern Michelson stellar interferometer which the Department has developed, the new instrument will be used in a wide range of astrophysical programmes. The siting, specification, design and costing of the instrument are outlined.