In maritime transportation, pilotage plays a crucial role in ensuring navigational safety. Marine pilots possess in-depth knowledge of local waters, currents and weather conditions, guiding ships safely through complex waterways. This expertise minimises risks such as collisions and groundings, thereby protecting both the ship and the environment, and promoting safe, efficient maritime traffic management. However, grounding accidents in pilotage waters can still lead to severe environmental, economic and operational damage, including oil spills, ecosystem harm and costly salvage efforts. Continuous improvements in pilotage are therefore vital to minimise these risks. In this study, with the combination of HFACS methodology and Apriori algorithm, factors contributing to grounding accidents in ships navigating with marine pilots and ship features are examined, and strong association rules among factors are achieved. The prominent factors discovered are ‘Ship–Marine Pilot Communication Problems’, ‘Inappropriate Passage Plan’, ‘Ineffective Usage of Bridge Equipment’, ‘Port Authority Resource Management’ and ‘Ineffective Teamwork’. Ship-marine pilot communication problems are the most prevalent factor in these derived rules which is appearing in 8 of 9 rules and exerting a substantial influence on the accidents. Inappropriate passage planning, identified in 6 rules, emerges as another significant and recurrent contributing factor. Based on the association rules, this study provides significant insights and actionable recommendations for stakeholders to prevent grounding accidents in marine pilot-assisted navigation.

We report the design and functionality of the Murchison Widefield Array Particle Detector Array (MWA PDA), an array of eight particle scintillation detectors deployed to Inyarrimanha Ilgari Bundara, the Murchison Radio-astronomy Observatory (MRO). The purpose of the instrument is to identify cosmic ray extensive air showers (EAS) occurring over the core of the MWA radio telescope and generate a trigger to allow radio data on the event to be captured and analysed. The system also acts as a pathfinder for a much larger instrument to be deployed in the core of the low-frequency component of the Square Kilometre Array, SKA-Low, by the SKA’s ultra-high-energy particles science working group. Here, we describe the instrument and associated infrastructure, which has been verified to comply with the strict radio-frequency emissions requirements of the MRO, and was deployed in November 2024. We present calibration data, which demonstrates the ability of each detector to identify individual atmospheric muons at the expected rate, and we characterise the temperature dependence of the system. We describe a sample of 35 500 EAS identified using multi-detector coincidence over a 13-d period, and show how the detector data can be used to reconstruct the arrival directions and approximate energies of these events. We conclude that the particle detector array can reliably trigger on and reconstruct EAS contained within the $\sim$$103 \times 90$ m$^2$ core region, arriving within 20$^{\circ}$ of zenith, at primary cosmic ray energies above $\sim$4 PeV. We have also verified that the detector array can generate triggers, allowing the capture of radio data from the MWA correlator for offline analysis.

We present the discovery of two intersecting radio shells, likely radio relics, surrounding a compact galaxy group dominated by a massive elliptical galaxy. The shells present as partial, edge-brightened rings with diameters of $\sim$240″ ($\sim$720 kpc) each and resemble a pair of odd radio circles. The central galaxy, WISEA J184105.19–654753.8, which shows signs of interactions, is radio bright, has a stellar mass of $3.1 \times 10^{11}$ M$_{\odot}$ (for a redshift of $z_\mathrm{phot}$ $\sim 0.18$) and is located in the intersect region. The double radio shell system, which we refer to as ORC J1841–6547, also known as ORC 6, was detected in 944 MHz radio continuum images obtained with Phased Array Feeds on the Australian Square Kilometre Array Pathfinder (ASKAP). The more prominent, north-western shell may be associated with an X-ray detection, while the weaker, south-eastern shell has no counterpart at non-radio wavelength. We propose outwards moving shocks from galaxy mergers driving into the intragroup medium, re-energising relic radio lobes, as a possible formation scenario for the observed radio shells. We conclude that at least some ORCs are shock-energised relics in the outskirts of galaxy groups, which originate during the merger evolution of the brightest group galaxy.

We present the characterisation, including a photometric redshift (photo-z) analysis, of the optical counterparts (CTPs) to over 45 000 bright (S856 MHz ≥ 30 mJy) compact radio sources, identified across all ASKAP First Large Absorption Survey in Hi (FLASH) fields observed up to April 2025. These sources constitute a large, homogeneous population of background continuum sightlines specifically selected to enable statistical studies of cold gas at intermediate redshifts of 0.42 ≤ z ≤ 1. As spectroscopic redshift measurements are not available for the majority of these candidate absorbers, we estimate photo-zs for the CTPs of all FLASH continuum sources cross-matched to the tenth data release of the DESI Legacy Imaging Surveys (LS10). Using these estimates, we establish the redshift distribution and find that approximately 13% of continuum sources lie at z < 0.42 (foreground), 35% within the detectability range of FLASH (‘in-band’), and 52% at z > 1 (background). We examine the subset of FLASH continuum sources with CTPs in the eROSITA X-ray survey, providing additional insight into their AGN content, multiwavelength properties, and environments. Finally, we discuss how this information can be used as a statistical prior to aid in distinguishing between associated and intervening Hi absorption systems and estimating the total comoving absorption path length of the survey, establishing a framework for incorporating redshift-based priors in future large radio absorption surveys. We release a catalogue of LS10 counterparts to FLASH continuum sources, providing photo-z estimates, associated uncertainties, and measures of redshift degeneracies.

Post-red and post-asymptotic giant stars in binary systems with main sequence companions, have periods in the range ∼50-2000 days, eccentricities as high as 0.6 and are surrounded by a circumbinary disc. Their orbital separations are small enough that the system must have gone through Roche lobe overflow when the primary was a full blown giant; Roche lobe overflow between a giant and a more compact companion tend to lead to a common envelope inspiral, leaving a circular orbit with periods much shorter than observed in these systems. In this first work in a series we explore to what extent a high mass ratio, q ≡ M2/M1, can lead to wider orbital separations, by carrying out a series of 3D, hydrodynamical CE binary interaction simulations with the smoothed particle hydrodynamics code PHANTOM. The giant is a 0.88 M⊙, 90 R⊙, red giant branch star and the companions have a range of masses such that q = 0.68 − 1.5. While larger q values result in wider post-CE separations, the upper limit we predict is only ∼ 50 R⊙, smaller than the observed range. The pre-CE mass transfer phase is longer for larger companion masses and around q ≳ 1 the nature of the CE inspiral changes significantly, showing greater stability, as predicted by analytical theory. However, this phase is not converged with respect to simulation resolution and it is expected that a higher resolution would lead to even more stability and a longer pre-inspiral phase. Despite more material flowing through the L2 and L3 Lagrange points for higher q values, with the potential for the formation of a circumbinary disc structure in this way, we conclude that, for our parameters, circumbinary discs are more likely to form from fall back of leftover bound envelope. Fall-back times are short (a few × 100 years) and fall-back discs extend between 0.5 and 5 au (outside the binary orbit), at which point the discs are likely to spread farther on short timescales via viscous torques. These discs have characteristics in line with those observed.

Following long periods of quiescence, low-mass X-ray binaries can exhibit intense X-ray outbursts triggered by instabilities within the accretion disk. These outbursts can sometimes be detected in optical wavelengths before being detected in X-ray, acting as an early onset warning and enabling a deep study of accretion disk properties informed by the lag between optical and X-ray rise. We explore the potential of Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) to detect these outbursts early through optical observations. We evaluate the capabilities of LSST based on currently planned survey cadence, filter-specific depth, and other observational factors that affect early detection. We develop and apply an extended metric to assess outburst detectability and recovery fraction. We find that despite inherent potential for early detection of XRB outbursts, the currently planned survey strategy makes it challenging to detect early onset of XRBs. Lastly, we demonstrate how this estimate can be used to infer the wider LMXB population in the Galaxy as the LSST progresses.

Underwater acoustic source localisation is essential for marine monitoring, navigation of autonomous underwater vehicles and underwater surveillance. Time Difference of Arrival (TDOA) localisation is attractive because it avoids absolute time synchronisation; however, its accuracy degrades in realistic underwater channels due to multipath, measurement noise and environmental variability (e.g. sound-speed mismatch) as well as sensor geometry limitations. This paper proposes an optimisation-based TDOA localisation framework that integrates: (i) Kalman filtering (KF) for dynamic tracking; (ii) extended Kalman filtering (EKF) to handle nonlinear measurement models; and (iii) nonlinear least-squares (NLS) minimisation to refine the source position. A parametric analysis is also presented by varying key system parameters – primarily noise level and measurement uncertainty – to quantify performance trade-offs in terms of localisation error and convergence behaviour. Simulation results (static and moving source cases) show that LS provides high accuracy for low-noise/static cases, while KF/EKF are more robust for dynamic and high-noise scenarios; EKF achieves the fastest error decay due to explicit nonlinear modelling. These results demonstrate the proposed framework’s effectiveness for robust underwater acoustic source localisation.

We describe standard forms for elements of the higher-dimensional Thompson groups nV arising from gridding subdivision processes. These processes lead to standard normal form descriptions for elements in these groups, and sizes of these standard forms estimate the word length with respect to finite generating sets. These gridded forms lead to standard algebraic descriptions as well, with respect to the both infinite and finite generating sets for these groups.

The increasing field of view of radio telescopes and improved data processing capabilities have led to a surge in the detection of Fast Radio Bursts (FRBs). The discovery rate of FRBs is already a few per day and is expected to increase rapidly with new surveys coming online. The growing number of events necessitates prioritized follow-up due to limited multi-wavelength resources, requiring rapid and automated classification. In this study, we introduce Frabjous, a deep learning framework for an automated morphology classifier with an aim towards enabling the prompt follow-up of anomalous and intriguing FRBs, and a comprehensive statistical analysis of FRB morphologies. Deep learning models require a large training set of each FRB archetype, however, publicly available data lacks sufficient samples for most FRB types. In this paper, we build a simulation framework for generating realistic examples of FRBs and train a network based on a combination of simulated and real data starting with the CHIME/FRB catalog. Applying our framework to the first CHIME/FRB catalog, we achieve an overall classification accuracy of approximately 55%, well over a random multiclass classification rate of 20% with five balanced classes during training. While this falls short of desirable performance, we critically discuss the limitations of our approach and propose potential avenues for improvement. Future work should explore strategies to augment training datasets and broaden the scope of FRB morphological studies, aiming for more accurate and reliable classification results.

The discovery of the galaxy ring known as the Council of Giants (CoG) highlights the need to explain such structures in the Local Universe. In the first paper of this series, we presented HINORA – a code to locate (ring-like) structures in 3D point sets – and used it to identify the CoG in the most complete observations of the Local Volume. Here, in Part II, we apply the same method to cosmological simulations to quantify the possible existence of such objects in the $\rm \Lambda$CDM model of structure formation. We analyse DM-only simulations with random and constrained initial conditions, selecting regions that reproduce the properties of the Local Group and Volume, respectively. In order to use the same selection criteria as previously done for observations, we relate K-band luminosities to halo masses through semi-empirical relations. After confirming that the selected regions from the simulations match the observed mass function and density of the Local Universe, we use HINORA to search for ring-like structures in them. We find that the existence of CoGs in $\rm \Lambda$CDM simulations is a rather unusual phenomenon. The observed CoG represents an anomaly of more than 2.7$\sigma$ from what is expected in the distribution of massive galaxies in $\rm \Lambda$CDM. These results hint that the CoG could either be a rare chance configuration or the imprint of physical processes at intermediate scales that standard DM-only simulations fail to capture.

Eccentric millisecond pulsar + helium white dwarf (MSP + He WD) systems have attracted increasing attention, with the rotationally delayed accretion-induced collapse (RD-AIC) scenario proposed as a possible formation channel. Given the similarity between the formation channels of He WDs and subdwarf B (sdB) stars, eccentric MSP + sdB binaries could also exist in the Galaxy, though none have been detected so far. Theoretical predictions of their properties would greatly aid in their discovery. Here, within the RD-AIC framework, I present predictions for their orbital parameters, including MSP mass, secondary mass, eccentricity, and orbital period. Based on two detailed binary population synthesis calculations, I estimate their Galactic birth rate to be $(0.67$–$1.5)\times10^\mathrm{-4}\mathrm{yr^\mathrm{-1}}$. Then, a very conservative upper limit for their total number in the Galaxy is 15 000, implying that the most optimistic fraction of eccentric MSP + sdB systems among all MSP + sdB populations could reach up to 55%. These systems are relatively young, with ages on the order of a few hundred Myr, and should therefore be found in relatively young environments. Furthermore, most MSPs in such eccentric binaries have masses below 1.5 M$_{\odot}$. I also briefly discuss their potential future applications in various astrophysical contexts.