Surface abundance observations of halo stars hint at the occurrence of r-process nucleosynthesis at low metallicity ([Fe/H] < -3), possibly within the first 108 yr after the formation of the first stars. Possible loci of early-Universe r-process nucleosynthesis are the ejecta of either black hole–neutron star or neutron star–neutron star binary mergers. Here, we study the effect of the inclination–eccentricity oscillations raised by a tertiary (e.g. a star) on the coalescence time-scale of the inner compact object binaries. Our results are highly sensitive to the assumed initial distribution of the inner binary semi-major axes. Distributions with mostly wide compact object binaries are most affected by the third object, resulting in a strong increase (by more than a factor of 2) in the fraction of fast coalescences. If instead the distribution preferentially populates very close compact binaries, general relativistic precession prevents the third body from increasing the inner binary eccentricity to very high values. In this last case, the fraction of coalescing binaries is increased much less by tertiaries, but the fraction of binaries that would coalesce within 108 yr even without a third object is already high. Our results provide additional support to the compact-binary merger scenario for r-process nucleosynthesis.

While automatic detection of point sources in astronomical images has experienced a great degree of success, less effort has been directed towards the detection of extended and low-surface-brightness features. At present, existing telescopes still rely on human expertise to reduce the raw data to usable images and then to analyse the images for non-pointlike objects. However, the next generation of radio telescopes will generate unprecedented volumes of data making manual data reduction and object extraction infeasible. Without developing new methods of automatic detection for extended and diffuse objects such as supernova remnants, bent-tailed galaxies, radio relics and halos, a wealth of scientifically important results will not be uncovered. In this paper we explore the response of the Circle Hough Transform to a representative sample of different extended circular or arc-like astronomical objects. We also examine the response of the Circle Hough Transform to input images containing noise alone and inputs including point sources.

Polarimetric studies of pulsars at low radio frequencies provide important observational insights into the pulsar emission mechanism and beam models, and probe the properties of the magneto-ionic interstellar medium (ISM). Aperture arrays are the main form of next-generation low-frequency telescopes, including the Murchison Widefield Array (MWA). These require a distinctly different approach to data processing (e.g. calibration and beamforming) compared to traditional dish antennas. As the second paper of this series, we present a verification of the MWA’s pulsar polarimetry capability, using two bright southern pulsars, PSRs J0742–2822 and J1752–2806. Our observations simultaneously cover multiple frequencies (76–313 MHz) and were taken at multiple zenith angles (ZA) during a single night for each pulsar. We show that the MWA can be reliably calibrated for ZA ≲45° and frequencies ≲270 MHz. We present the polarimetric profiles for PSRs J0742–2822 and J1752–2806 at frequencies lower than 300 MHz for the first time, along with an analysis of the linear polarisation degree and pulse profile evolution with frequency. For PSR J0742–2822, the measured degree of linear polarisation shows a rapid decrease at low frequencies, in contrast with the generally expected trend, which can be attributed to depolarisation effects from small-scale, turbulent, magneto-ionic ISM components. This effect has not been widely explored for pulsars in general and will be further investigated in future work.

SN1991bg-like supernovae are a distinct subclass of thermonuclear Type Ia supernovae (SNe Ia). Their spectral and photometric peculiarities indicate that their progenitors and explosion mechanisms differ from ‘normal’ SNe Ia. One method of determining information about supernova progenitors we cannot directly observe is to observe the stellar population adjacent to the apparent supernova explosion site to infer the distribution of stellar population ages and metallicities. We obtain integral field observations and analyse the spectra extracted from regions of projected radius $\sim\,\text{kpc}$ about the apparent SN explosion site for 11 91bg-like SNe in both early- and late-type galaxies. We utilise full-spectrum spectral fitting to determine the ages and metallicities of the stellar population within the aperture. We find that the majority of the stellar populations that hosted 91bg-like supernovae have little recent star formation. The ages of the stellar populations suggest that that 91bg-like SN progenitors explode after delay times of >6 Gyr, much longer than the typical delay time of normal SNe Ia, which peaks at $\sim$1 Gyr.

It has generally been accepted that moving type IV bursts are generated as synchrotron radiation from energetic electrons high in the solar corona (Boischot and Denisse 1957). At 80 MHz the peak brightness temperature is usually ~ 108 K and the radiation becomes highly circularly polarized as the burst decays. This has led several authors (Kai 1969; Dulk 1970, 1973; Schmahl 1972; Robinson 1974, 1977; Nelson 1977) to the conclusion that the radiation comes from mildly relativistic (~ 100 keV) electrons and occurs at low harmonics of the gyro-frequency (gyro-synchrotron radiation). We present evidence of moving type IV bursts at 43, 80 and 160 MHz with brightness temperatures of ~ 109 K, and one at 43 MHz as high as 1010 K. The number (~ 1033) of energetic (≥ 1 MeV) electrons which is required in order to explain such high brightness temperatures by incoherent gyro-synchrotron emission is very large and near the upper limit for the number of fast electrons accelerated in the second phase of a solar flare. If amplification takes place a smaller number of electrons with energies ~ 100 keV would be required.

We present an application of Mathematical Morphology (MM) for the classification of astronomical objects, both for star/galaxy differentiation and galaxy morphology classification. We demonstrate that, for CCD images, 99.3 ± 3.8% of galaxies can be separated from stars using MM, with 19.4 ± 7.9% of the stars being misclassified. We demonstrate that, for photographic plate images, the number of galaxies correctly separated from the stars can be increased using our MM diffraction spike tool, which allows 51.0 ± 6.0% of the high-brightness galaxies that are inseparable in current techniques to be correctly classified, with only 1.4 ± 0.5% of the high-brightness stars contaminating the population. We demonstrate that elliptical (E) and late-type spiral (Sc-Sd) galaxies can be classified using MM with an accuracy of 91.4 ± 7.8%. It is a method involving fewer ‘free parameters’ than current techniques, especially automated machine learning algorithms. The limitation of MM galaxy morphology classification based on seeing and distance is also presented. We examine various star/galaxy differentiation and galaxy morphology classification techniques commonly used today, and show that our MM techniques compare very favourably.

The outburst and storm of more than four hours’ duration that accompanied the importance 2 flare beginning at 0h25m U.T. on 9 June 1968 were observed at 80 MHz with the Culgoora radioheliograph. More than 104 heliograms in both senses of circular polarization were recorded at one-second intervals both as cathode-ray-tube photographs and as digital characters on magnetic tape. It is the purpose of this preliminary account to summarize these observations and bring attention to a new phenomenon observed before the start of the flare.

We model a massless viscous disk using smoothed particle hydrodynamics (SPH) and note that it evolves according to the Lynden-Bell & Pringle (1974) theory until a non-axisymmetric instability develops at the inner edge of the disk. This instability may have the same origin as the instability of initially axisymmetric viscous disks discussed by Lyubarskij, Postnov & Prokhorov (1994). To clarify the evolution we evolved single and double rings of particles. It is actually inconsistent with the SPH scheme to set up a single ring as an initial condition because SPH assumes a smoothed initial state. As would be expected from an SPH simulation, the ring rapidly breaks up into a band. We analyse the stability of the ring and show that the predictions are confirmed by the simulation.

The radio installations at Culgoora Observatory evolved from the work carried out at Dapto field station between 1952 and 1965—which in turn was based on earlier observations. The basic instrument at Dapto was a radiospectrograph which produced two solar spectra per second over a frequency range originally of 40-210 MHz and finally of 5-2000 MHz. Until 1957 the Dapto radio spectrograph was the only one operating in the world and it fell upon this instrument to reveal many of the spectral phenomena which are now well known. The spectrograph observations referred to the total flux from the Sun observations with high directivity began at Dapto in 1958 with the introduction of a swept-frequency interferometer which measured the one-dimensional (east-west) positions of bursts and their approximate angular size over a continuous range of frequencies between 40 and 70 MHz. The results obtained from this combination of spectrograph and interferometer indicated that great advances would be made in our knowledge and understanding of the phenomena if two-dimensional metre-wavelength pictures of the Sun could somehow be recorded at short time intervals of about Is—again in combination with spectrographic observations. This requirement led to the start of the radioheliograph project. One requirement for this instrument was a site with linear dimensions of the order of 3x3 km. This was far too large for the Dapto site and a new site was selected at Culgoora in the north-west plains of New South Wales. The virtues of this site are its size, flatness, freedom from flooding, low radio noise level and accessibility from Sydney by air transport. Its sunshine and optical-seeing properties also made it a highly desirable site for optical observations, and developments assumed a new significance when Dr. Giovanelli and his optical colleagues decided to join us at the same observatory.

The visually close binary system HD25811 is analysed to estimate its physical and geometrical parameters in addition to its spectral type and luminosity class. The method depends on obtaining the best fit between the entire observational spectral energy distribution (SED) of the system and synthetic SEDs created by atmospheric modelling of the individual components, consistent with the system's modified orbital elements. The parameters of the individual components of the system are derived as: Taeff = 6850 ± 50 K, Tbeff = 7000 ± 50 K, log ga = 4.04 ± 0.10, log gb = 4.15 ± 0.10, Ra = 1.96 ± 0.20 R⊙, Rb = 1.69 ± 0.20 R⊙, Mav = 1.m97 ± 0.20, Mbv = 2.m19 ± 0.20, La = 7.59 ± 0.70L⊙, Lb = 6.16 ± 0.70L⊙ with dynamical parallax $\pi (\textrm {mas})=5.095\pm 0.095$. The analysis shows that the system consists of a 1.55M⊙ F2 subgiant star and a less evolved 1.50M⊙ F1 secondary subgiant star with ages around 2 Gy formed by fragmentation. Synthetic magnitudes of both components were calculated under Johnson-Cousins, Strömgren, and Tycho photometrical systems.

Photometric observations in V and I bands and low-dispersion spectra of 10 ultrashort-period binaries (NSVS 2175434, NSVS 2607629, NSVS 5038135, NSVS 8040227, NSVS 9747584, NSVS 4876238, ASAS 071829-0336.7, SWASP 074658.62+224448.5, NSVS 2729229, NSVS 10632802) are presented. One of them, NSVS 2729229, is newly discovered target. The results from modelling and analysis of our observations revealed that (i) eight targets have overcontact configurations with considerable fill-out factor (up to 0.5), while NSVS 4876238 and ASAS 0718-03 have almost contact configurations; (ii) NSVS 4876238 is rare ultrashort-period binary of detached type; (iii) all stellar components are late dwarfs; (iv) the temperature difference of the components of each target does not exceed 400 K; (v) NSVS 2175434 and SWASP 074658.62 + 224448.5 exhibit total eclipses and their parameters could be assumed as well determined; (v) NSVS 2729229 shows emission in the Hα line. Masses, radii, and luminosities of the stellar components were estimated by the empirical relation ‘period, orbital axis’ for short- and ultrashort-period binaries. We found linear relations mass–luminosity and mass–radius for the stellar components of our targets.

Relatively small amounts (typically between 2 and 200 ppm) of presolar grains have been preserved in the matrices of chondritic meteorites. The measured abundances of the different types of grains are highly variable from one chondrite to another, but are higher in unequilibrated chondrites that have experienced little or no aqueous alteration and/or metamorphic heating than in processed meteorites. A general overview of the abundances measured in presolar grains (particularly the recently identified presolar silicates) contained in primitive chondrites is presented. Here we will focus on the most primitive chondrite groups, as typically the highest measured abundances of presolar grains occur in primitive chondrites that have experienced little thermal metamorphism. Looking at the most aqueously altered chondrite groups, we find a clear pattern of decreasing abundance of presolar silicate grains with increasing levels of aqueous alteration. We conclude that measured abundances of presolar grains in altered chondrites are strongly biased by their peculiar histories. Scales quantifying the intensity of aqueous alteration and shock metamorphism in chondrites could correlate with the content of presolar silicates. To do this it would be required to infer the degree of destruction or homogenization of presolar grains in the matrices of primitive meteorites. To get an unbiased picture of the relative abundance of presolar grains in the different regions of the protoplanetary disk where first meteorites consolidated, future dedicated studies of primitive meteorites, IDPs, and collected materials from sample-return missions (like e.g. the planned Marco Polo) are urgently required.

The gas added to and removed from galaxies over cosmic time greatly affects their stellar populations and star formation rates. QSO absorption line studies in close QSO/galaxy pairs create a unique opportunity to study the physical conditions and kinematics of this gas. Here we present new Hubble Space Telescope (HST) images of the QSO/galaxy pair, 3C 232/NGC 3067. The quasar spectrum contains a Lyman limit (NHi = 1 × 1020 cm−2) absorption system (LLS) at cz = 1421 km s−1 that is associated with the nearby Sab galaxy NGC 3067. Previous work identifies this absorber as a high-velocity cloud (HVC) in NGC 3067 but the kinematics of the absorbing gas, infalling or outflowing, were uncertain. The HST images presented here establish the orientation of NGC 3067 and so establish that the LLS/HVC is infalling. Using this system as a prototype, we extend these results to higher-z MgII/LLS to suggest that Mgii/LLSs are a sightline sampling of the so-called ‘cold mode accretion’ (CMA) infalling onto luminous galaxies. To match the observed MgII absorber statistics, the CMA must be more highly ionised at higher redshifts. The key observations needed to further the study of low-z LLSs is HST UV spectroscopy, for which a new instrument, the Cosmic Origins Spectrograph, has just been installed greatly enhancing our observational capabilities.

A procedure is introduced to recognise sunspots automatically in solar full-disk photosphere images obtained from Huairou Solar Observing Station, National Astronomical Observatories of China. The images are first pre-processed through Gaussian algorithm. Sunspots are then recognised by the morphological Bot-hat operation and Otsu threshold. Wrong selection of sunspots is eliminated by a criterion of sunspot properties. Besides, in order to calculate the sunspots areas and the solar centre, the solar limb is extracted by a procedure using morphological closing and erosion operations and setting an adaptive threshold. Results of sunspot recognition reveal that the number of the sunspots detected by our procedure has a quite good agreement with the manual method. The sunspot recognition rate is 95% and error rate is 1.2%. The sunspot areas calculated by our method have high correlation (95%) with the area data from the United States Air Force/National Oceanic and Atmospheric Administration (USAF/NOAA).

Evolutionary calculations have been made for a star of initial mass 17.5 M⊙ in order to emulate the evolution of the precursor of SN1987A. The results give good agreement (i) with the observed properties of Sanduleak -69°202 (star 1) when the model reaches the supernova epoch, and (ii) with the observed distribution of red and blue supergiants in the LMC. Mass loss throughout the life of the star at rates reasonably consistent with observed values is required to produce these results. At the time of explosion, the supernova has a mass of only ∼ 5.4 M⊙ and it is surrounded by about 8 M⊙ of wind material in a shell of ∼0.4 pc radius.

The Australia Telescope and Anglo-Australian Telescope were used in May 2000 to record the radio and optical emissions from the dMe flare star Proxima Centauri. Eight bright optical flares over a two-day interval resulted in no detectable excess short-term radio emission at 1.38 and 2.50 GHz. However, a slowly declining 1.38 GHz emission over the two-day interval was nearly 100% right circular polarised and was restricted to a relatively narrow bandwidth with total intensity (I) and circular polarisation (V) varying significantly over the 104 MHz receiver bandwidth. These are the first observations to show that highly-polarised narrowband flare star emission can persist for several days. This signature is attributed to sources of coherent radio emission in the star's corona. Similarities with various solar radio emissions are discussed; however, it is not possible with the existing observations to distinguish between fundamental plasma emission and electron–cyclotron maser emission as the responsible mechanism.

The Antarctic Plateau holds great promise for optical astronomy. One relatively unstudied feature of the polar night sky for optical astronomical observing is the potential contamination of observations by aurorae. In this study we analyse auroral measurements at South Pole Station and show that during an average winter season, the auroral contribution to the B band sky brightness is below 21.9 B mag arcsec−2 for 50% of the observing time. In V band, the median sky brightness contribution is 20.8 mag arcsec−2 during an average winter. South Pole Station is situated within the auroral zone and experiences strong and frequent auroral activity. The Antarctic locations of Dome C and Dome A are closer to the geomagnetic pole where auroral activity is greatly reduced compared with that of South Pole Station. Calculations based on satellite measurements of electron flux above the Antarctic Plateau are used to show that at Dome C, the contribution to sky background in the B and V bands is up to 3.1 mag less than that at the South Pole. The use of notch filters to reduce the contribution from the strongest auroral emission lines and bands is also discussed. The scientific potential of an extremely large telescope located at Dome C is discussed, with reference to the effect that auroral emissions would have on particular astronomical observations.

We have compiled a catalogue of H ii regions detected with the Murchison Widefield Array between 72 and 231 MHz. The multiple frequency bands provided by the Murchison Widefield Array allow us identify the characteristic spectrum generated by the thermal Bremsstrahlung process in H ii regions. We detect 306 H ii regions between 260° < l < 340° and report on the positions, sizes, peak, integrated flux density, and spectral indices of these H ii regions. By identifying the point at which H ii regions transition from the optically thin to thick regime, we derive the physical properties including the electron density, ionised gas mass, and ionising photon flux, towards 61 H ii regions. This catalogue of H ii regions represents the most extensive and uniform low frequency survey of H ii regions in the Galaxy to date.

We review observations of diffuse ionised gas (DIG) in edge-on spiral galaxies. Deep imaging has revealed a variety of morphologies for ‘extraplanar’ (above the HII region layer) or ‘halo’ DIG: some show widespread prominent layers of truly diffuse gas and filamentary structures, others show just one patch or a few patches of extraplanar emission, while still others show no detectable extraplanar DIG at all. The key galactic property which appears to govern the prominence of the DIG layer is the star-formation activity. Smaller-scale connections between DIG and local star formation activity can be seen in some of the galaxies.

DIG halos are also related to radio continuum, X-ray and HI halos. Those galaxies with the most prominent DIG layers also have the most prominent radio halos. In NGC 891, there are spatial correlations between extraplanar DIG, radio emission, X-ray emission and HI, and these in turn are related to the underlying disk star-formation activity.

Progress on identifying the sources of ionisation and heating of the gas has come from spectroscopy, imaging in different emission lines, and Fabry–Perot observations. By comparing with theoretical predictions, much evidence is found for photoionisation by disk stars as the primary ionisation and heating mechanism, but recent observations are beginning to point towards the need for additional sources of ionisation and/or heating.

The accumulation, compression, and cooling of the ambient interstellar medium (ISM) in large-scale flows powered by OB cluster feedback can drive the production of dense molecular clouds. We review the current state of the field, with a strong focus on the explicit modelling and observation of the neutral ISM. Magnetohydrodynamic simulations of colliding ISM flows provide a strong theoretical framework in which to view feedback-driven cloud formation, as do models of the gravitational fragmentation of expanding shells. Rapid theoretical developments are accompanied by a growing body of observational work that provides good evidence for the formation of molecular gas via stellar feedback—both in the Milky Way and the Large Magellanic Cloud. The importance of stellar feedback compared with other major astrophysical drivers of dense gas formation remains to be investigated further, and will be an important target for future work.