We present the second data release (DR2) of Spectra and Polarisation in Cutouts of Extragalactic sources from RACS (SPICE-RACS). SPICERACS DR2 is derived from the third low-band epoch of the Rapid ASKAP Continuum Survey (RACS-low3) and covers the entire sky from the South celestial pole up to a declination of +49°; approximately 87.5% of the celestial sphere. We produce ‘cutout’ spectral cubes in Stokes I, Q, U around 4 million radio sources and extract spectra towards 5 million radio components. Across our observed band of 799.5 to 1087.5MHz we find an rms noise of ∼ 200 μJy/PSF, an angular resolution of ∼ 15″, and residual wide-field instrumental polarisation on the order of 0.1 %. After de-duplication, our polarisation catalogue contains the detection of 2.5×105 (3.4×105) Faraday rotation measures (RM) for components with a linearly polarised signal above 8σ (6σ). This places SPICE-RACS DR2 as the largest single RM catalogue ever produced by nearly an order of magnitude; the number of RMs in our catalogue alone is ∼ 5 times larger than every previous RM catalogue combined. Our resulting RM grid has an areal density of , providing an effective ‘resolution’ of ∼ 23′, and reveals striking features across the sky. The broad-band RMs have a median uncertainty of ∼2 radm−2, and include complexity metrics and information from the time domain. The breadth and quality of the SPICE-RACS DR2 dataset will enable a new generation of RM science. Further, SPICE-RACS will provide an ideal reference for forthcoming deep polarisation surveys such as the ASKAP POSSUM survey. All of our data products are publicly available on the CSIRO Data Access Portal (DAP) and the CSIRO ASKAP Science Data Archive (CASDA).

We develop a general relativistic, one-dimensional model of advection-dominated accretion flows (ADAFs) around Schwarzschild black holes, incorporating the full viscous shear tensor and all components of the heat flux four vector. This framework allows for a consistent treatment of anisotropic conduction in curved space time. Our results highlight the dominant role of radial and temporal heat flux components, while the vertical component, which is commonly emphasised in earlier studies, has negligible impact. Thermal conduction is found to significantly modify the disc structure in inner regions, enhancing thermal pressure and vertical expansion while reducing density. At larger radii, conduction effects fade and disc properties converge. The energy budget remains advection-dominated, with viscous heating exceeding radiative cooling and a substantial portion of energy carried inward by advection. Additionally, stronger inflow and higher angular momentum intensify all thermal processes through enhanced compression and shear. Our results affirm that realistic modelling of ADAFs around black holes demands inclusion of both anisotropic and fully general relativistic effects in heat transport and viscosity. We further show that the accretion flow exhibits transonic behaviour, characterised by a relativistic Mach number that increases inward and crosses unity as the flow approaches the black hole, marking the transition from subsonic to supersonic regimes. Moreover, the weak Coulomb coupling in such radiatively inefficient flows leads naturally to a two-temperature plasma, in which ions and electrons evolve quasi-independently, with the ion component dominating the thermodynamic structure.

Fast radio bursts (FRBs) are bright (Jansky-level) and short-duration ($\sim$1 ms) flashes of extragalactic origin. Observations of single events have now been complemented by large-area surveys, delivering FRB catalogues and enabling the first population studies. The Northern Cross (NC) radio interferometer is one of the instruments performing observations of FRBs. In this work, we present the Italian Northern Cross Atlas of Radio Transients (INCART), a public platform for the distribution of data products from the NC. INCART makes available to the community the FRBs observed by the NC through manageable frequency-time series datasets and catalogues with best-fit physical parameters. The design of INCART guarantees the possibility of scientific re-analysis of the FRB properties, in view also of future releases of the processing pipeline. Furthermore, INCART focuses on long-term storage optimisation, which is a key aspect of state-of-the-art instrumentation. Public access to the FRB data from the NC maximises the legacy value of the collection, facilitates the synergy with other publicly available catalogues, and fosters research group collaborations.

We report the discovery of a new long-period radio transient, ASKAP J142431.2–612611, with a 36 min period, identified in the Australian SKA Pathfinder Evolutionary Map of the Universe survey. We detected pulsed emission from ASKAP J142431.2–612611 over a period of eight days during follow-up observations with the Australia Telescope Compact Array, after which the source appears to have switched off. No optical or near-infrared counterpart is detected in archival surveys or in targeted Gemini South FLAMINGOS-2 observations. During its active state, the source exhibits a stable pulse profile with fractional polarisation consistent with 100%, evolving from elliptically to linearly polarised and tracing a well-defined great-circle trajectory on the Poincaré sphere. We show that this behaviour is consistent with fully linearly polarised intrinsic emission modified by propagation through a linearly polarised birefringent medium. This discovery expands the known population of long-period transients and highlights the intermittent nature of their activity. We discuss the implications for proposed models of long-period transients and outline future observations needed to constrain the origin of their intermittency and polarisation properties.

Precision geodesy relies on the stability of the International Celestial Reference Frame (ICRF), yet its reference sources, Active Galactic Nuclei (AGN), exhibit intrinsic changes in source structure that can manifest as apparent shifts in their astrometric positions. The high-precision radio measurements used to maintain the ICRF therefore provide a powerful means to investigate the astrophysical mechanisms driving these position changes. In particular, the observed astrometric variability offers a unique opportunity to link positional shifts in AGN to high-energy astrophysical processes. We therefore investigated the relationship between the astrometric positions of ICRF AGN and their $\gamma$-ray emission. We measured the positional offsets of radio cores relative to the third realisation of the ICRF at both S/X (2.3/8.4 GHz) and K (24 GHz) bands and compared them to Fermi-LAT (Large Area Telescope) $\gamma$-ray fluxes within $\pm$30 days of the radio observation. Out of an initial sample of 92 radio sources selected for having extensive radio astrometric observations, we identified 57 that met our selection criteria of having sufficient overlapping $\gamma$-ray data points to allow for regression analysis. We find a high incidence of statistically significant ($p\lt0.05$) power-law correlations, with $\sim$ 90% of sources exhibiting this behaviour. The nature of this correlation is complex: we observe both positive and negative correlations, and the sign of the correlation can differ between the two frequency bands for the same source. To explain the correlations, we tested several scenarios, including variable $\gamma$-ray emission locations, changes in nuclear opacity, and variations in jet position angle. Our analysis reveals no single, universally applicable explanation. Instead, the results suggest that the observed correlation is driven by a complex interplay of multiple physical mechanisms, the dominance of which likely varies between sources. A search for time lags between the radio position offsets and $\gamma$-ray fluxes revealed tentative – and highly caveated – evidence for a time-delay in only five sources, with no evidence in other sources. A statistical comparison with the Optical Characteristics of Astrometric Radio Sources (OCARS) catalogue shows that, although our sample is biased towards optically brighter sources with better-constrained astrometric solutions due to their larger number of radio observations, it remains representative of the broader AGN population in terms of redshift distribution.

Lunar impact flashes provide a direct means of estimating the flux of centimetre-sized meteoroids impacting the lunar surface. However, 25–60 frames per second imaging typical of most monitoring programs limit the ability to resolve the rapid temporal evolution of the impact process, while the integration of Earthshine background restricts the detection of faint flashes. In this work, we present high-speed observations of lunar impact flashes captured at 200 and 250 FPS using the Zadko Telescope in Western Australia. We resolve the light curves of four confirmed events, revealing complex morphologies, some of which are not well modelled by simple exponential decays. One event was simultaneously detected by a second observer using a 50 FPS system, revealing a significantly faster brightness drop in the high-speed data that cannot be explained by spectral differences alone, indicating temporal integration of the vapour plume and subsequent ejecta. Our data also indicates that the initial flash intensity (representing the vapour plume) exhibits significantly less variance across events than the total luminous energy. Furthermore, we found no statistical correlation between the initial luminous energy and the total integrated energy of the flashes in this data, suggesting that the physical mechanism driving the initial vapour expansion may be physically decoupled from the longer-duration glow driven by the cooling ejecta. High temporal resolution combined with high sensitivity are therefore essential for accurately characterising the physical properties of the impactor and distinguishing the initial vapour plume from the subsequent incandescent cooling phase, although a significantly larger dataset is required to definitively constrain these mechanisms.

We present FIRES, a polarised shot-noise (PSN) framework that models fast radio burst (FRB) dynamic spectra as the incoherent superposition of Gaussian microshots with varying polarisation angles (PAs). Applied to the CRAFT bursts FRB 20191001A and FRB 20240318A, FIRES can reproduce key spectro-polarimetric behaviours seen in these data: scattering suppresses PA variability on the trailing edge, while the leading edge preferentially retains intrinsic structure when sufficient signal-to-noise is present. We quantify this behaviour using the PA variance ratio $\mathcal{R}_\psi$ and explore the joint plane of measured linear polarisation fraction $\Pi_L$ versus PA variance to identify allowed regions of microshot number N, intrinsic PA dispersion $\sigma_\psi$, and intrinsic linear fraction $\Pi_{L,0}$ at fixed signal-to-noise. This restricts these combinations permitted within the adopted shot-noise framework. For FRB 20191001A, the data are consistent with an extended parameter space, reflecting degeneracies between intrinsic PA structure, microshot superposition, scattering, finite sampling, noise, and the assumed microshot-property distributions. FRB 20240318A occupies a more restricted region, favouring fewer microshots and larger intrinsic PA dispersion. By combining an emission-mechanism-independent forward-modeling framework with minimal assumptions and observational constraints, FIRES facilitates qualitative and quantitative exploration of how microshot superposition, scattering, finite sampling, and noise can shape observed FRB polarimetry under the PSN model.

We report the detection of a long-period companion to the nearby solar-type star HD 38973 using precision radial-velocity (RV) measurements. The RV data reveal a coherent Keplerian signal with a period of $\sim$3 000 days and moderate eccentricity, yielding a minimum mass in the sub-Jovian regime. We complement the RV analysis with astrometric constraints from the Hipparcos–Gaia Catalog of Accelerations (HGCA). Although no significant proper-motion anomaly is detected for HD 38973, the absence of an astrometric signal provides an informative upper limit on the companion mass. By combining the RV posterior with the HGCA likelihood, we rule out high-mass solutions at low inclinations and derive a robust upper bound on the true companion mass. We find the best-fitting true mass to be $0.240_{-0.040}^{+0.102}\,M_{\mathrm{Jup}}$, on an orbit with period $2\,733^{+210}_{-190}$ days, making HD 38973b a likely cold Saturn. This study highlights the diagnostic power of astrometric non-detections when combined with precision radial velocities, demonstrating that meaningful constraints on companion masses can be obtained even in the absence of a detected astrometric signal.