We present the third data release for the Galactic and Extragalactic All-Sky Murchison Widefield Array eXtended (GLEAM-X) survey, covering $\approx 3\,800$ deg$^2$ of the southern Galactic Plane (GP) with ${233}^{\circ} \lt l \lt {44}^{\circ}$ and $|b| \lt {11}^{\circ}$ across a frequency range of 72–231 MHz divided into 20 sub-bands. GLEAM-X observations were taken using the ‘extended’ Phase-ii configuration of the Murchison Widefield Array (MWA), which features baselines ranging from approximately 12 m to 5 km. This configuration limits sensitivity to the diffuse structure of the GP, with an angular resolution range of about $45^{''}$ to $2^{'}$. To achieve lower noise levels while being sensitive to a wide range of spatial scales ($45^{''} - {15}^{\circ}$), we combined these observations with the previous Galactic and Extragalactic All-Sky Murchison Widefield Array (GLEAM) survey. For the area covered, we provide images spanning the whole frequency range. A wide-band image over 170–231 MHz, with RMS noise of $\approx\;$3–6 mJy beam$^{-1}$ and source position accuracy within 1 arcsec, is then used to perform source-finding, which yields 98 207 elements measured across $20 \times 7.68$ MHz frequency bands. The catalogue is 90$\%$ complete at 50 mJy within ${233}^{\circ} \lt l \lt {324}^{\circ}$ and at 125 mJy in ${290}^{\circ} \lt l \lt {44}^{\circ}$, while it is $99.3\%$ reliable overall. All the images and the catalogue are available online for download.

Radio galaxy remnants are a rare subset of the radio-loud active galactic nuclei (RLAGN) population, representing the quiescent phase in the RLAGN lifecycle. Despite their observed scarcity, they offer valuable insights into the AGN duty cycle and feedback processes. Due to the mega-year timescales over which the RLAGN lifecycle takes place, it is impossible to observe the active to remnant transition in real-time. Numerical simulations offer a solution to follow the long-term evolution of RLAGN plasma. In this work, we present the largest suite (to date) of three-dimensional, hydrodynamic simulations studying the dynamic evolution of the active-to-remnant transition and explore the mechanisms driving cocoon evolution, comparing the results to the expectations of analytic modelling. Our results show key differences between active and remnant sources in both cluster environments and in lower-density group environments. We find that sources in low-density environments can remain overpressured well into the remnant phase. This significantly increases the time for the remnant lobe to transition to a buoyant regime. We compare our results with analytic expectations, showing that the long-term evolution of radio remnants can be well captured for remnants whose expansion is largely pressure-driven if the transition to a coasting phase is assumed to be gradual. We find that remnants of low-powered progenitors can continue to be momentum-driven for about 10 Myr after the jets switch-off. Finally, we consider how the properties of the progenitor influence the mixing of the remnant lobe and confirm the expectation that the remnants of high-powered sources have long-lasting shocks that can continue to heat the surrounding medium.

Several radio telescopes have been planned or proposed to be deployed on the Lunar farside in the coming years. These will observe the unexplored ultra-long wavelengths of the electromagnetic spectrum from the lunar farside’s unique radio-quiet and ionosphere-free environment. One such lunar radio array is the NASA-funded concept - the Farside Array for Radio Science Investigations of the Dark Ages and Exoplanets (FARSIDE). FARSIDE will operate over 100 kHz to 40 MHz with 128 spatially non-co-located orthogonal pairs of antenna nodes distributed over a 12 × 12 km area in a four-arm spiral configuration. Being on the lunar farside, this radio interferometer will be deployed by tele-operated rovers. The rover deployment mode could lead to a phase offset between each of the two orthogonally polarised antenna elements in the array, which are typically co-located. In this paper, we quantify the effects of such antenna phase offsets on the polarisation response and imaging performance of the lunar radio array. Modelling and analysing the FARSIDE dipole beams with and without offset, we find the latter leads to additional leakages into Stokes U and V corresponding to Muller matrix terms of M2(0,1,2,3) and M3(0,1,2,3). Using a custom simulation pipeline to incorporate all four Stokes beams of spatially co-located and non-co-located dipoles, we produce visibilities and simulated images for the GLEAM (GaLactic and Extragalactic All-sky MWA) sky model through the FARSIDE array. We find that for a pure Stokes I input sky, the output image maximum Stokes V/I flux ratio for the offset case has increased to 2.5% versus 0.05% for the co-located case. The additional Stokes V needs to be corrected since the detection of Electron Cyclotron Maser (ECM) emissions from exoplanets requires high-fidelity Stokes V measurements.

This paper reports the discovery and follow-up of four candidate redback spider pulsars: GPM J1723$-33$, GPM J1734$-28$, GPM J1752$-30$, and GPM J1815$-14$, discovered with the Murchison Widefield Array (MWA) from an imaging survey of the Galactic Plane. These sources are considered to be redback candidates based on their eclipsing variability, steep negative spectral indices, and potential Fermi $\gamma$-ray associations, with GPM J1723$-33$ and GPM J1815$-14$ lying within a Fermi 95$\%$ error ellipse. Follow-up pulsation searches with MeerKAT confirmed pulsations from GPM J1723$-33$, while the non-detections of the other three are likely due to scattering by material ablated from their companion stars. We identify possible orbital periods by applying folding algorithms to the light curves and determine that all sources have short orbital periods ($\lt$24 h), consistent with redback spider systems. Following up on the sources at multiple radio frequencies revealed that the sources exhibit frequency-dependent eclipses, with longer eclipses observed at lower frequencies. We place broad constraints on the eclipse medium, ruling out induced Compton scattering and cyclotron absorption. Three sources are spatially consistent with optical sources in the Dark Energy Camera Plane Survey imaging, which may contain the optical counterparts. Each field is affected by strong dust extinction, and follow-up with large telescopes is needed to identify the true counterparts. Identifying potential radio counterparts to four previously unassociated Fermi sources brings us closer to understanding the origin of the unexplained $\gamma$-ray excess in the Galactic Centre.

Post-AGB and post-RGB binaries with stable circumbinary discs provide key insights into late stellar and disc evolution, revealing how binary interactions shape disc structure and stellar surface composition. A defining trait of such systems is the observed underabundance of refractory elements in the stellar photosphere relative to volatile elements– photospheric chemical depletion– resulting from the star accreting volatile-rich circumstellar gas. In this study, we investigated the link between photospheric depletion and disc evolution by focusing on post-AGB/post-RGB binaries with low infrared excess (hereafter “faint disc” targets). We analysed high-resolution optical spectra from HERMES/Mercator and UVES/VLT for 6 Galactic and 2 LMC targets. Using E-iSpec, we homogeneously derived atmospheric parameters and chemical abundances of 29 elements from carbon to europium, and included NLTE corrections for 15 elements from carbon to barium that we calculated using pySME and pre-computed grids of departure coefficients. All targets exhibit ‘saturated’ depletion patterns, which we characterised using two-piece linear fits defined by three parameters: initial metallicity ([M/H]0), turn-off temperature (Tturn–off), and depletion scale (∇100K). Among several findings, we highlight the bimodal distribution of Tturn–off in faint disc targets, which allows classification into two subgroups analogous to full discs with continuous, optically thick dust (Tturn–off > 1 100 K), and transition discs with inner clearing (Tturn–off < 1 100 K). Our results imply that faint disc targets likely represent the final stages of disc dissipation, highlighting the diversity of depletion profiles, the complexity of disc-binary interactions, and the need to understand the rarity and evolution of faint disc systems.

We investigate the effect of turbulent magnetic fields on the observed spectral properties of synchrotron radio emission in large-scale radio galaxy lobes. We use three-dimensional relativistic magnetohydrodynamic simulations of fast, high-powered jets to study the structure of the lobe magnetic fields and how this structure affects the radio spectrum of the lobes. It has previously been argued that lobe ages inferred from radio spectra underestimate the true ages of radio galaxies due to re-acceleration of electrons in the lobe, mixing of electron populations, or the presence of turbulent magnetic fields in the lobes. We find that the spectral ages with and without accounting for the lobe magnetic field structure are consistent with each other, suggesting that mixing of radiating populations of different ages is the primary cause of the underestimation of radio lobe ages. By accounting for the structure of lobe magnetic fields, we find greater spectral steepening in the equatorial regions of the lobe. We demonstrate that the assumptions of the continuous injection, Jaffe-Perola, and Tribble models for radio lobe spectra do not hold in our simulations, and we show that young particles with high magnetic field strengths are the dominant contributors to the overall radio lobe spectrum.

We present a new method to calculate the polarised synchrotron emission of radio Active Galactic Nuclei (AGN) sources using magnetic field information from 3-dimensional relativistic magnetohydrodynamical (RMHD) simulations. Like its predecessor, which uses pressure as a proxy for the magnetic field, this method tracks the spatially resolved adiabatic and radiative loss processes using the method adapted from the Radio AGN in Semi-analytic Environments formalism. Lagrangian tracer particles in RMHD simulations carried out using the PLUTO code are used to track the fluid quantities of each ‘ensemble of electrons’ through time to calculate the radio emissivity ex situ. By using the magnetic field directly from simulations, the full set of linear Stokes parameters I, Q, and U can be calculated to study the synthetic radio polarisation of radio AGN sources. We apply this method to a suite of RMHD simulations to study their polarisation properties. The turbulent magnetic field present in radio lobes influences the emission, causing a complex clumpy structure that is visible at high resolution. Our synthetic polarisation properties are consistent with observations; we find that the fractional polarisation is highest (approximately 50%) at the lobe edges. We show that for the same source, the integrated and mean fractional polarisation depends on viewing angle to the source. At oblique viewing angles the behaviour of the integrated and mean fractional polarisation over time depends on the morphology of the jet cocoon. Using Faraday rotation measures, we reproduce known depolarisation effects such as the Laing-Garrington depolarisation asymmetry in jets angled to the line of sight. We show that the hotspots and hence the Fanaroff–Riley classification become less clear with our new, more accurate method.

It is explained why relatively gas-poor ultra-diffuse galaxies (UDGs), a subset of IC 3475 galaxy types, do not have unexpectedly large sizes but large sizes that are in line with expectations from the curved size-luminosity relation defined by brighter early-type galaxies (ETGs). These UDGs extend the faint end of the (absolute magnitude, )-log(Sérsic index, n) and -(central surface brightness, µ0) relations defined by all ETGs, leading to the large effective half-light radii, Re, in these UDGs. It is detailed how the scatter in µ0, at a given , relates to variations in the galaxies’ values of n and effective surface brightness, µe. These variations map into changes in Re and produce the scatter about the -Re relation at fixed . Similarly, the scatter in , at fixed µ0 and n, can be mapped into changes in Re. The suggestion that there may be two types of relatively gas-poor UDGs appears ill-founded, arising from the scatter about the -µ0 relation. The increased scatter about the faint end of the -Re relation and the smaller scatter about -(isophotal radii, Riso) relations are explained. Artificial and potentially misleading size-luminosity relations for UDGs are also addressed. Finally, expected trends with dynamical mass, and evolutionary pathways towards relatively gas-rich galaxies, are briefly discussed. Hopefully, the understanding presented here will prove helpful for interpreting the many low surface brightness galaxies that the Large Synoptic Survey Telescope will detect.

In this study, we investigate the chemical enrichment and structural evolution of the isolated elliptical relic galaxy Mrk1216 through X-ray observations. As a red-nugget relic, Mrk1216 provides a rare window into the early Universe, owing to its minimal interaction with the surrounding environment. Using data from the XMM-Newton telescope, we model the X-ray emission of its interstellar medium to derive radial temperature and abundance profiles. We find that the central region exhibits an elevated [Mg/Fe] ratio compared to typical early-type galaxies, consistent with a brief but intense star formation episode during its early assembly – a hallmark of relic systems. The nearly flat SNIa ratio profile ($R_{Ia} \sim 0.17$) extending to $\sim0.42R_{500}$ supports an early-enrichment scenario. These results highlight the importance of relic galaxies as benchmarks for studying early galaxy evolution and chemical enrichment. Future high-resolution missions and more advanced theoretical models incorporating more realistic initial mass functions are needed to fully assess their implications.

We report detection and analysis of the largest ever low-frequency sample of Crab giant pulses (GPs) detected in frequency band 200 – 231.25 MHz. In total about ∼95000 GPs were detected, which, to our knowledge is the largest low-frequency sample of Crab GPs presented in the literature. The observations were performed between 2024-12-14 and 2025-03-31 with the Engineering Development Array 2, a prototype station of the low-frequency Square Kilometre Array telescope. The fluence distribution of GPs in the entire sample is very well characterised with a single power law N(F) ∝ Fα, where α =−3.17 ± 0.02 for all GPs, and αMP = −3.13 ± 0.02 and αIP =−3.59 ± 0.06 for GPs at the phases of the main pulse and low-requency interpulse respectively. We do not observe flattening of the fluence distribution at the higher fluences. Although, the index of the power law fluence distribution remained approximately constant over the observing period, the normalisation of the distribution was strongly anti-correlated (coefficient ≈ −0.9) with the scatter broadening time. The timescale (∼ weeks) of these variations indicates that intrinsic GP emission was modulated by the refractive scintillation as the signals propagated through the Crab Nebula and ISM. As a result, the measured fluence distribution was augmented for lower (τ ≈ 2 ms) and diminished for higher (τ ≈ 5 ms) scatter broadening time τ causing the GP detection rate to vary between 3000 and 100 per hour respectively (the correlation coefficient ≈-0.9). Furthermore, for the first time at low-frequencies we observe indications of positive correlation (correlation coefficient ≈0.7) between the scatter broadening time (τ) and dispersion measure. Our modelling favours the screen size ∼ 10−5 pc with mean electron density ∼ 400e−cm−3 located within 100 pc from the pulsar (Crab Nebula or Perseus arm of the Milky Way galaxy). The observed frequency scaling of the scattering broadening time β ≈ −3.6 ± 0.1 (where τ ∝ νβ) is in agreement with the previous measurements. The observed maximum spectral luminosities ∼ 1025 erg/Hz/s approach those of the weakest pulses from some repeating Fast Radio Bursts (FRBs). However, the distribution of pulse arrival times is consistent with a purely random Poisson process, and we do not find evidence of clustering. Overall, our results agree with the current views that GPs from extra-galactic Crab-like pulsars can be responsible for some very weak repeating FRBs, but cannot explain the entire FRB population. Finally, these results demonstrate an enormous transient science potential of individual SKA-Low stations, which can be unlocked by milli-second all-sky imaging.

Pulsar timing arrays (PTAs) are Galactic-scale nanohertz-frequency gravitational wave (GW) detectors. Recently, several PTAs have found evidence for the presence of GWs in their datasets, but none of them have achieved a community-defined definitive (> 5σ) detection. Here, we identify limiting noise sources for PTAs and quantify their impact on sensitivity to GWs under different observing and noise modelling strategies. First, we search for intrinsic pulse jitter in a sample of 89 millisecond pulsars (MSPs) observed by the MeerKAT Pulsar Timing Array and obtain new jitter measurements for 20 MSPs. We then forecast jitter noise in pulsars for the future SKA-Mid telescope, finding that the timing precision of many of the best-timed MSPs would be dominated by jitter noise. We then consider dispersion measure variations from the interstellar medium and find that their effects are best mitigated by modelling them as a stationary Gaussian process with a power-law spectrum. Improving upon the established hasasia code for PTA sensitivity analysis, we assess the timing potential of the lower frequency UHF-band (544–1088 MHz) of MeerKAT and find a potential increase in GW background sensitivity by ≈ 8%, relative to observing at L-band. We show that this improvement relies on assumptions on the propagation through the interstellar medium, and highlight that if observing frequency-dependent propagation effects, such as scattering noise, are present, where noise is not completely correlated across observing frequency, then the improvement is significantly diminished. Using the multi-frequency receivers and sub-arraying flexibility of MeerKAT, we find that focussed, high-cadence observations of the best MSPs can enhance the sensitivity of the array for both the continuous GWs and stochastic GW background. These results highlight the role of MeerKAT and the MPTA in the context of international GW search efforts.

Until now, the study of unresolved main-sequence binary stars in globular clusters has been possible almost exclusively in their central regions with deep Hubble Space Telescope (HST) observations. We present the first detection of unresolved main-sequence binary stars in the outer field of 47 Tucanae using Rubin Observatory’s Data Preview 1 (DP1). Our analysis exploits deep i vs. $g-i$ colour–magnitude diagrams beyond the cluster’s half-light radius, reaching almost to the tidal radius. The high-quality photometry allowed to identify unresolved binaries with mass ratios q larger than 0.7. The derived binary fraction of $f_\mathrm{bin} (q\gt0.7)=0.016\pm0.005$ stands in contrast to the significantly lower values in the cluster innermost regions, as measured from HST photometry. This result provides new empirical input for testing physical processes that drive the formation and evolution of binary stars in globular clusters. It also demonstrates Rubin’s unique wide-field and high-precision photometric capabilities to address a broader range of outstanding questions in star cluster research. Future full data releases will enable to significantly expand the study of dense stellar systems across the Milky Way.

Magnetic massive stars are stars of spectral types O, B and A that harbour ∼ kG strength (mostly dipolar) surface magnetic fields. Their non-thermal radio emission has been demonstrated to be an important magnetospheric probe, provided the emission is fully characterised. A necessary step for that is to build a statistically significant sample of radio-bright magnetic massive stars. In this paper, we present the ‘VAST project to study Magnetic Massive Stars’ or VAST-MeMeS that aims to achieve that by taking advantage of survey data acquired with the Australian SKA Pathfinder telescope. VAST-MeMeS is defined under the ‘Variables and Slow Transients’ (VAST) survey, although it also uses data from other ASKAP surveys. We found radio detections from 48 magnetic massive stars, out of which, 14 do not have any prior radio detections. We also identified 9 ‘Main-sequence Radio Pulse Emitter’ candidates based on variability and circular polarisation of flux densities. The expanded sample suggests a slightly lower efficiency in the radio production than that reported in earlier work. In addition to significantly expanding the sample of radio-bright magnetic massive stars, the addition of flux density measurements at ≲ 1 GHz revealed that the spectra of incoherent radio emission can extend to much lower frequencies than that assumed in the past. In the future, radio observations spanning wide frequency and rotational phase ranges should be conducted so as to reduce the uncertainties in the incoherent radio luminosities. The results from these campaigns, supplemented with precise estimations of stellar parameters, will allow us to fully understand particle acceleration and non-thermal radio production in large-scale stellar magnetospheres.

The Hector Galaxy Survey is a new optical integral field spectroscopy (IFS) survey currently using the Anglo-Australian Telescope (AAT) to observe up to 15,000 galaxies at low redshift (z < 0.1). The Hector instrument employs 21 optical fibre bundles feeding into two double-beam spectrographs, AAOmega and the new Spector spectrograph, to enable wide-field multi-object IFS observations of galaxies. To efficiently process the survey data, we adopt the data reduction pipeline developed for the SAMI Galaxy Survey, with significant updates to accommodate Hector’s dual-spectrograph system. These enhancements address key differences in spectral resolution and other instrumental characteristics relative to SAMI, and are specifically optimised for Hector’s unique configuration. We introduce a two-dimensional arc fitting approach that reduces the root-mean-square (RMS) velocity scatter by a factor of 1.2–3.4 compared to fitting arc lines independently for each fibre. The pipeline also incorporates detailed modelling of chromatic optical distortion in the wide-field corrector, to account for wavelength-dependent spatial shifts across the focal plane. We assess data quality through a series of validation tests, including wavelength solution accuracy (1.2–2.7 km s–1 RMS), spectral resolution (FWHM of 1.2–1.4 Å for Spector), throughput characterisation, astrometric precision (≲ 0.03 arcsec median offset), sky subtraction residuals (1–1.6% median continuum residual), and flux calibration stability (4% systematic offset when compared to Legacy Survey fluxes). We demonstrate that Hector delivers high-fidelity, science-ready datasets, supporting robust measurements of galaxy kinematics, stellar populations, and emission-line properties, and provide examples. Additionally, we address systematic uncertainties identified during the data processing and propose future improvements to enhance the precision and reliability of upcoming data releases. This work establishes a robust data reduction framework for Hector, delivering high-quality data products that support a broad range of extragalactic studies.

The millisecond pulsar PSR J1713+0747 is a high-priority target for pulsar timing array experiments due to its long-term timing stability, and bright, narrow pulse profile. In April 2021, PSR J1713+0747 underwent a significant profile change event, observed by several telescopes worldwide. Using the broad bandwidth and polarimetric fidelity of the Ultra-Wideband Low-frequency receiver on Murriyang, CSIRO’s Parkes radio telescope, we investigated the long-term spectro-polarimetric behaviour of this profile change in detail. We highlight the broad-bandwidth nature of the event, which exhibits frequency dependence that is inconsistent with cold-plasma propagation effects. We also find that spectral and temporal variations are stronger in one of the orthogonal polarisation modes than the other, and observe mild variations (∼ 3 – 5 σ significance) in circular polarisation above 1400MHz following the event. However, the linear polarisation position angle remained remarkably stable in the profile leading edge throughout the event. With over three years of data post-event, we find that the profile has not yet recovered back to its original state, indicating a long-term asymptotic recovery, or a potential reconfiguration of the pulsar’s magnetic field. These findings favour a magnetospheric origin of the profile change event over a line-of-sight propagation effect in the interstellar medium.

This paper extends our previous study of the gyro-emission by energetic electrons in the magnetospheres of rapidly rotating, magnetic massive stars, through a quantitative analysis of the role of cooling by Coulomb collisions with thermal electrons from stellar wind material trapped within the centrifugal magnetosphere (CM). For the standard, simple CM model of a dipole field with aligned magnetic and rotational axes, we show that both gyro-cooling along magnetic loops and Coulomb cooling in the CM layer have nearly the same dependence on the magnitude and radial variation of magnetic field, implying then that their ratio is a global parameter that is largely independent of the field. Analytic analysis shows that, for electrons introduced near the CM layer around a magnetic loop apex, collisional cooling is more important for electrons with high pitch angle, while more field-aligned electrons cool by gyro-emission near their mirror point close to the loop base. Numerical models that assume a gyrotropic initial deposition with a gaussian distribution in both radius and loop co-latitude show the residual gyro-emission is generally strongest near the loop base, with highly relativistic electrons suffering much lower collisional losses than lower-energy electrons that are only mildly relativistic. Even for cases in which the energy deposition is narrowly concentrated near the loop apex, the computed residual emission shows a surprisingly broad distribution with magnetic field strength, suggesting that associated observed radio spectra should generally have a similarly broad frequency distribution. Finally, we briefly discuss the potential applicability of this formalism to magnetic ultracool dwarfs (UCDs), for which Very Long Baseline Interferometry (VLBI) observations indicate incoherent radio emission to be concentrated around the magnetic equator, in contrast to our predictions here for magnetic hot stars. We suggest that this difference could be attributed to UCDs having either a lower ambient density of thermal electrons, or more highly relativistic non-thermal electrons, both of which would reduce the relative importance of the collisional cooling explored here.

We present microsecond-resolution, coherently dedispersed, polarimetric measurements of 35 fast radio bursts (FRBs) detected during the Commensal Real-time ASKAP Fast Transients (CRAFT) incoherent sum (ICS) survey with the Australian Square Kilometre Array Pathfinder (ASKAP). We find a wide diversity of time–frequency morphology and polarisation properties broadly consistent with those of currently known non-repeating FRBs. The high S/N and fine time-resolution of our data however reveals a wealth of new information. Key results include (i) the distribution of scattering timescales, ${{{\unicode{x03C4}}_\textrm{obs}}}$, is limited purely by instrumental effects, with no downturn at high ${{{\unicode{x03C4}}_\textrm{obs}}}$ as expected from a log-normal distribution; (ii) for the 29 FRBs with known redshift, there is no detectable correlation between ${{{\unicode{x03C4}}_\textrm{obs}}}$ and dispersion measure (DM) fluctuations about the Macquart relation, in contrast to expectations from pulsar scattering–DM relations; (iii) all FRBs probably have multiple components, and at least a large fraction have variable PA, the identification of which is limited by scattering; (iv) at least half of all FRBs exhibit PA microstructure at 200 $\mu{}$s–200 ns timescales, with behaviour most closely resembling a sub-category of Crab main pulses; (v) that there is a break in the FRB circular polarisation distribution at Stokes $V \gtrsim 20$%, which is suggestive of a discrete sub-population.

We present a potential test of the origin of the $\gamma$-ray Galactic Centre Excess (GCE). We demonstrate how gravitational microlensing by stellar mass objects along the line of sight to the Galactic Bulge can distinguish between the possibility of extensive emission due to dark matter self-annihilation from more prosaic astrophysical sources, namely millisecond pulsars. Such an astrophysical origin would result in emission from a population of small, currently unresolved point-like sources – in contrast to the expected smoother emission resulting from dark matter annihilation. Given that the scale of gravitational microlensing, that is, the Einstein radius for stellar mass lenses, and hence, the degree of induced magnification, is sensitive to the size of the emitting region, such microlensing will induce time variability in the emission of astrophysical sources, whereas $\gamma$-ray emission from dark matter annihilation will effectively be immune to such influences. However, we find that detecting microlensing-induced variability requires significantly greater sensitivity than that of current or planned $\gamma$-ray detectors. For a small population of bright GCE sources, more than an order-of-magnitude increase in effective area over Fermi-LAT would be required, with events remaining extremely rare. For a large population of faint sources, events would occur multiple times a year, but would only be detectable with a four-order-of-magnitude improvement. Whilst microlensing might not be a definitive test of the origin of the GCE, in future observations, it may prove useful in determining the properties of any point-like source population.

We present a catalogue of 3 557 Double Radio sources associated with Active Galactic Nuclei (DRAGNs) from the First Pilot Survey of the Evolutionary Map of the Universe (EMU), observed at 944 MHz with the Australian Square Kilometre Array Pathfinder (ASKAP) telescope, covering 270 deg$^{2}$. We have extracted and identified each source by eye, tagged it with a morphological type and measured its parameters. The resulting catalogue will be used in subsequent papers to explore the properties of these sources, to train machine-learning algorithms for the detection of these sources in larger fields, and to compare with the results of Citizen Science projects, with the ultimate goal of understanding the physical processes that drive DRAGNs. Compared with earlier, lower sensitivity, catalogues, we find more diffuse structure and a plethora of more complex structures, ranging from wings of radio emission on the side of the jets, to types of object which have not been seen in earlier observations. As well as the well-known FR1 and FR2 sources, we find significant numbers of rare types of radio source such as Hybrid Morphology Radio Sources and one-sided jets, as well as a wide range of bent-tail and head-tail sources.

The upcoming Square Kilometre Array Low Frequency (SKA-Low) interferometer will have the required sensitivity to detect the 21 cm line from neutral hydrogen during the Epoch of Reionisation (EoR). In preparation, we investigated the suitability of different fields for EoR science with the 21 cm line, using existing observations of candidate fields from the Murchison Widefield Array (MWA). Various image and calibration metrics were extracted from archival MWA observations centred on $z \sim 6.8$. We explore the usefulness of these metrics and compare their behaviour between different fields of interest. In addition, a theoretical approach to quantifying the impact of different fields on the power spectrum is also provided. Gain uncertainties were calculated based on the positions of the calibrators within the beam. These uncertainties were then propagated into visibilities to produce cylindrical power spectra for various fields. Using these metrics in combination with the power spectra, we confirm that EoR0 ($\text{R.A.} = 0\,\mathrm{deg}$, $\text{Dec} = {-}27.0\,\mathrm{deg}$) is an ideal EoR field and discuss the interesting behaviour of other fields.