We have used the University of Tasmania Mt Pleasant 26-m radio telescope to investigate the polarisation characteristics of a sample of strong 6.7 GHz methanol masers, the first spectral line polarisation observations to be undertaken with this instrument. As part of this process we have developed a new technique for calibrating linear polarisation spectral line observations. This calibration method gives results consistent with more traditional techniques, but requires much less observing time on the telescope. We have made the first polarisation measurements of a number of 6.7 GHz methanol masers and find linear polarisation at levels from a few to 10% in most of the sources we observed, consistent with previous results. We also investigated the circular polarisation produced by Zeeman splitting in the 6.7 GHz methanol maser G9.62+0.20 to get an estimate of the line of sight magnetic field strength of 35±7 mG.

The Hirsch h-index is now widely used as a metric to compare individual researchers. To evaluate it in the context of Australian astronomy, the h-index for every member of the Astronomical Society of Australia (ASA) is found using NASA's Astrophysics Data System Bibliographic Services. Percentiles of the h-index distribution are detailed for a variety of categories of ASA members, including students. This enables a list of the top ten Australian researchers by h-index to be produced. These top researchers have h-index values in the range 53<h<77, which is less than that recently reported for the American Astronomical Society membership. We suggest that membership of extremely large consortia such as the Sloan Digital Sky Survey may partially explain the difference. We further suggest that many student ASA members with large h-index values have probably already received their Ph.D. and need to upgrade their ASA membership status. To attempt to specify the h-index distribution relative to opportunity, we also detail the percentiles of its distribution by years since Ph.D. award date. This shows a steady increase in h-index with seniority, as can be expected.

The Sydney University Stellar Interferometer (SUSI) has been used to make a new determination of the angular diameter of Sirius A. The observations were made at an effective wavelength of 694.1 nm and the new value for the limb-darkened angular diameter is 6.048 ± 0.040 mas (± 0.66%). This new result is compared with previous measurements and is found to be in excellent agreement with a conventionally calibrated measurement made with the European Southern Observatory's Very Large Telescope Interferometer (VLTI) at 2.176 μm (but not with a second globally calibrated VLTI measurement). A weighted mean of the SUSI and first VLTI results gives the limb-darkened angular diameter of Sirius A as 6.041 ± 0.017 mas (± 0.28%). Combination with the Hipparcos parallax gives the radius equal to 1.713 ± 0.009 R⊙. The bolometric flux has been determined from published photometry and spectrophotometry and, combined with the angular diameter, yields the emergent flux at the stellar surface equal to (5.32 ± 0.14) × 108 W m−2 and the effective temperature equal to 9845 ± 64 K. The luminosity is 24.7 ± 0.7 L⊙.

A novel spectrum-extraction method based on a 2-D Gaussian model is proposed in this paper. First, the flat images are employed to fit the model parameters in the spatial orientation and the calibration lamp images are used to fit the model parameters in the wavelength orientation. Then normalized 2-D models are obtained by combining the parameters of the two orientations. The flux-extraction algorithm is based on least-square theory and the 2-D model. Through experiments, the extracted spectra by our method have a stronger ability to reduce noise than the 1-D spectrum extraction method.

Binary systems, in particular eclipsing binaries, are essential sources of knowledge of the fundamental properties of stars. The ages of binaries, members of open clusters, are constrained by their own fundamental properties and by those of the hosting cluster. The ages of eleven open clusters are here found by constructing models for the components of twelve eclipsing binaries. The difference between the ages we find and the ages of the clusters derived from isochrone fitting is up to 40%. For the binary system V497 Cep in NGC 7160, the difference is about 100%. Binary systems whose primary component is about to complete its main-sequence lifetime, such as V453 Cyg and V906 Sco, are the most suitable systems for age determination. Using model results for these stars, we derive an expression for sensitive and uncomplicated relative age determination of binary systems (age divided by the main-sequence lifetime of the primary star). The expression is given as a logarithm of radii ratio divided by a logarithm of mass ratio. Two advantages of this expression are that: (i) it is nearly independent of the assumed chemical composition of the models because of the appearance of the ratio of radii; and (ii) the ratios of radii and masses are observationally much more precise than their absolute values. We also derive another expression using luminosities rather than radii and compare results.

The next generation 2-μm sky survey should target nascent galaxies in the epoch of reionization for spectroscopic followup on large telescopes. A 2.5-m telescope at a site on the Antarctic plateau has advantages for this purpose and for southern hemisphere infrared surveys in general.

Anovel profile detection method is proposed for astronomical fiber spectrum data with low signalto-noise ratio. This approach can be applied to the pretreatment for 2-D astronomical spectrum data before the extraction of spectra. The Wigner bispectrum, a classical higher-order spectrum analysis method, is introduced and applied to deal with the spectrumsignal in this article.After analyzing the Wigner higher-order spectra distribution of the target profile signal, the combination of the Wigner bispectrum algorithm and the fast Fourier transform algorithm is used to weaken the effect of the noise to obtain more accurate information. Both the reconstruction method of the Wigner bispectrum and inverse fast Fourier transform are used to acquire the detection signal. At the end of this paper, experiments with both simulated and observed data based on the Large Sky Area Multi-Object Fiber Spectroscopy Telescope project are presented to demonstrate the effectiveness of the proposed method.

We present VLA 21-cm observations of the spiral galaxy ESO 481-G017 to determine the nature of remote star formation traced by an Hii region found 43 kpc and ∼800 km s−1 from the galaxy center (in projection). ESO 481-G017 is found to have a 120 kpc Hi disk with a mass of 1.2 × 1010M⊙ and UV GALEX images reveal spiral arms extending into the gaseous disk. Two dwarf galaxies with Hi masses close to 108M⊙ are detected at distances of ∼200 kpc from ESO 481-G017 and a Hi cloud with a mass of 6 × 107M⊙ is found near the position and velocity of the remote Hii region. The Hii region is somewhat offset from the Hi cloud spatially and there is no link to ESO 481-G017 or the dwarf galaxies. We consider several scenarios for the origin of the cloud and Hii region and find the most likely is a dwarf galaxy that is undergoing ram pressure stripping. The Hi mass of the cloud and Hi luminosity of the Hii region (1038.1 erg s−1) are consistent with dwarf galaxy properties, and the stripping can trigger the star formation as well as push the gas away from the stars.

In this study, new observations and some results of statistical analyses are presented. The largest flare data set of DO Cep in the literature has been obtained with 89 flares detected in 67.61 hours of U-band flare patrol. First of all, the observations demonstrated that the star is one of the most active flare stars in respect to the computed flare frequency. Secondly, using the independent samples t-test, the detected flares were classified into two subtypes, and then they were modelled. Analysing the models demonstrated that the fast and slow flares occurring on the star can be separated with a critical value of the ratio of their decay time to rise time. The critical value was computed as 3.40. According to this value, the fast flare rate is 20.22%, while the slow flare rate is 79.78%. Besides, there is a 39.282 times difference between the energies of these two types of flares. However, the flare equivalent durations versus the flare rise times increase in similar ways for both groups. In addition, all the flares were modelled with the one-phase exponential association function. Analysing this model, the plateau value was found to be 2.810. Moreover, the half-life value was computed as 433.1 s from the model. The maximum flare rise time was found to be 1164 s, while the maximum flare total duration was found to be 3472 s. The results of the flare timescales indicate that the geometry of the flaring loop on the surface of the star might be similar to those seen on analogues of DO Cep. Consequently, considering both the half-life value and flare timescales, the flares detected on the surface of DO Cep get maximum energy in longer times, while the geometries of the flaring loops or areas get smaller.

Astronomy is entering a new era of discovery, coincident with the establishment of new facilities for observation and simulation that will routinely generate petabytes of data. While an increasing reliance on automated data analysis is anticipated, a critical role will remain for visualization-based knowledge discovery. We have investigated scientific visualization applications in astronomy through an examination of the literature published during the last two decades. We identify the two most active fields for progress — visualization of large-N particle data and spectral data cubes—discuss open areas of research, and introduce a mapping between astronomical sources of data and data representations used in general-purpose visualization tools. We discuss contributions using high-performance computing architectures (e.g. distributed processing and GPUs), collaborative astronomy visualization, the use of workflow systems to store metadata about visualization parameters, and the use of advanced interaction devices. We examine a number of issues that may be limiting the spread of scientific visualization research in astronomy and identify six grand challenges for scientific visualization research in the Petascale Astronomy Era.

Although originally classified as galaxies, Ultra-Compact Dwarfs (UCDs) have many properties in common with globular star clusters. The debate on the origin and nature of UCDs, and the recently discovered ultra-faint dwarf spheroidal (dSph) galaxies which contain very few stars, has motivated us to as the question ‘What is a galaxy?’ Our aim here is to promote further discussion of how to define a galaxy and, in particular, what separates it from a star cluster. Like most previous definitions, we adopt the requirement of gravitationally bound stellar system as a minimum. In order to distinguish a dwarf galaxy from a globular cluster, we discuss other possible requirements, such as a minimum size, a long two-body relaxation time a satellite system, the presence of complex stellar populations and non-baryonic dark matter. We briefly mention the implications of the adoption of each of these definitions. Some special cases of objects with a ambiguous nature are also discussed. Finally, we give our favoured criteria, and in the spirit of ‘collective wisdom’, invite readers to vote on their prefered definition of a galaxy via a dedicated website.

We present new imaging data and archival multiwavelength observations of the little-studied emission nebula K 1-6 and its central star. Narrow-band images inHα (+[N II]) and [O III] taken with the Faulkes Telescope North reveal a stratified, asymmetric, elliptical nebula surrounding a central star which has the colours of a late G or early K-type subgiant or giant. GALEX ultraviolet images reveal a very hot subdwarf or white dwarf coincident in position with this star. The cooler, optically dominant star is strongly variable with a period of 21.312± 0.008 days, and is possibly a high-amplitude member of the RS CVn class, although an FK Com classification is also possible. Archival ROSAT data provide good evidence that the cool star has an active corona. We conclude that K 1-6 is most likely an old bona fide planetary nebula at a distance of ∼1.0 kpc, interacting with the interstellar medium, and containing a binary or ternary central star. The observations and data analyses reported in this paper were conducted in conjunction with Year 11 high school students as part of an Australian Research Council Linkage Grant science education project, denoted Space To Grow, conducted jointly by professional astronomers, educational researchers, teachers, and high-school students.

We apply a new, expanded compilation of extragalactic source Faraday rotation measures (RM) to investigate the broad underlying magnetic structure of the Galactic disk at latitudes ∣b∣ ≲15° over all longitudes l, where our total number of RMs is comparable to those in the combined Canadian Galactic Plane Survey (CGPS) at ∣b∣ < 4° and the Southern Galactic Plane (SGPS) ∣b∣<1.5°. We report newly revealed, remarkably coherent patterns of RM at ∣b∣≲15° from l∼270° to ∼90° and RM(l) features of unprecedented clarity that replicate in l with opposite sign on opposite sides of the Galactic center. They confirm a highly patterned bisymmetric field structure toward the inner disc, an axisymmetic pattern toward the outer disc, and a very close coupling between the CGPS/SGPS RMs at ∣b∣≲3° (‘mid-plane’) and our new RMs up to ∣b∣∼15° (‘near-plane’). Our analysis also shows the vertical height of the coherent component of the disc field above the Galactic disc's mid-plane—to be ∼1.5 kpc out to ∼6 kpc from the Sun. This identifies the approximate height of a transition layer to the halo field structure. We find no RM sign change across the plane within ∣b∣∼15° in any longitude range. The prevailing disc field pattern and its striking degree of large-scale ordering confirm that our side of the Milky Way has a very organized underlying magnetic structure, for which the inward spiral pitch angle is 5.5°±1° at all ∣b∣ up to ∼12° in the inner semicircle of Galactic longitudes. It decreases to ∼0° toward the anticentre.