We have analysed photometric data from a sample of pulsating stars observed by the Transiting Exoplanet Survey Satellite. By applying Fourier and prewhitening techniques, we extracted the significant frequencies for each star. We investigated the presence of rotationally split multiplets and evaluated frequency spacings using the Kolmogorov-Smirnov test. These analyses allow us to estimate stellar parameters such as the large frequency spacing, which in turn provides insights into the stellar mean densities. However, identifying clear multiplets and frequency spacings in δ Scuti stars remains challenging due to the complexity of their oscillation spectra. Our rotationally-split mode findings are yet to be confirmed, while the K-S test revealed no convincing large frequency spacings that could be used toward mass estimation. We derived orbital periods for stars we identified to be in binary systems. We provide spectral type classifications to confirm the δ Sct and/or γ Dornature of the stars we found. Out of 43 stars presented in this paper, 18 are identified as δ Sct/γ Dor hybrids (including five candidates), 20 as δSct stars, one as a γ Dor star and four as binary systems without any signature of pulsation.

AM CVn stars are ultra-compact semi-detached binaries consisting of a white dwarf primary and a hydrogen-depleted secondary. In this paper we present spectroscopic and photometric results of 15 transient sources pre-classified as AM CVn candidates. Our analysis confirms 9 systems of the type AM CVn, 3 hydrogen-rich cataclysmic variables (accreting white dwarfs with near-main-sequence stars for donors) and 3 systems that could be evolved cataclysmic variables. Eight of the AM CVn stars are analysed spectroscopically for the first time, which increases the number of spectroscopically confirmed AM CVns by about 10%. TESS data revealed the orbital period of the AM CVn star ASASSN-20pv to be Porb =27.282 min, which helps to constrain the possible values of its mass ratio. TESS also helped to determine the superhump periods of one AM CVn star (ASASSN-19ct, Psh = 30.94 min) and two cataclysmic variables we classify as WZ Sge stars (Psh = 90.77 min for ZTF18aaaasnn and Psh =91.6 min for ASASSN-15na).We identified very different abundances in the spectra of the AM CVns binaries ASASSN-15kf and ASASSN-20pv (both Porb ∼ 27.5 min), suggesting different type of donors. Six of the studied AM CVns are X-ray sources, which helped to determine their mass accretion rates. Photometry shows that the duration of all the superoutbursts detected in the AM CVns is consistent with expectations from the disc instability model. Finally, we provide refined criteria for the identification of new systems using all-sky surveys such as LSST.

Interferometric localisation of transients and pulsars via tied-array beam processing is challenging and can be limited by the native spatial resolution achievable by the instrument, especially at low frequencies and for compact interferometers. Knowledge of the telescope primary and tied-array beam patterns allows the exploitation of the beam structures and the relationship to measured quantities, such as signal-to-noise ratio, through radio direction finding techniques. The additional information provides a “super-resolved” localisation (i.e., where the precision is much better than the native spatial resolution) of a source when there are multiple detections in adjacent tied-array beams. We demonstrate this approach using the Murchison Widefield Array (MWA) and its voltage capture and tied-array processing capabilities, with a specific focus on how it benefits the on-going Southern-sky MWA Rapid Two-metre pulsar survey as it starts producing more candidates requiring follow-up. Examples of localisations with previously discovered MWA pulsars which were subsequently localised via imaging with higher spatial resolution interferometers are used to validate the process, along with localisations of a sample of known pulsars to demonstrate the robustness of the method and its uncertainty estimation.

A handful of planetary systems hosting a Hot Jupiter have been subsequently found to also host long-period giant planets. These “cold Jupiters,” giant planets residing beyond the snow line (∼3au), play an important role in the dynamical evolution of the system as a whole. In this work, we investigate the detectability of cold Jupiters around a sample of 28 well-studied Hot Jupiter host stars to estimate the occurrence rate of this distinctive system architecture. We perform extensive simulations using the combination of all publicly available radial velocity (RV) data for those stars with synthetic RV data. The synthetic data test observing strategies along three axes: cadence, duration, and measurement precision. For each scenario, we determine detection limits based on the semi-major axis at which a 1 Jupiter mass planet would be recovered 50% of the time. We find the following: 1) the existing RV data are remarkably insensitive to these Hot Jupiter/Cold Jupiter pairs; 2) the total baseline over which an observational campaign is carried out is the dominant factor in our ability to detect cold Jupiters; and 3) the results are relatively insensitive to the individual RV measurement precision. We conclude that metre-class telescopes with lower RV precision are ideally suited to surveying Hot Jupiter-cold Jupiter systems.

The intrinsic width and scattering distributions of fast radio bursts (FRBs) inform on their emission mechanism and local environment, and act as a source of detection bias and, hence, an obfuscating factor when performing FRB population and cosmological studies. Here, we utilise a sample of 29 FRBs with measured high-time-resolution properties and known redshift, which were detected using the Australian Square Kilometre Array Pathfinder (ASKAP) by the Commensal Real-time ASKAP Fast Transients Survey (CRAFT), to model these distributions. Using this sample, we estimate the completeness bias of intrinsic width and scattering measurements, and fit the underlying, de-biased distributions in the host rest-frame. In no case do our model fits prefer a down-turn at high values of the intrinsic distributions of either parameter in the 0.01–40 ms range probed by the data. Rather, when assuming a spectral scattering index of α = –4, we find that the intrinsic scattering distribution at 1GHz is consistent with a log-uniform distribution above 0.04 ms, and that this functional form is strongly favoured over the lognormal descriptions used by previous works. We also find that the intrinsic width distribution rises as a Gaussian in log-space in the 0.03 – 0.3 ms range, with a log-uniform distribution above that slightly preferred to a lognormal distribution. This confirms previous works suggesting that FRB observations are currently strongly width- and scattering-limited, and we encourage FRB searches to be extended to higher values of time-width. It also implies a bias in FRB host galaxy studies, although the form of that bias is uncertain. Finally, we find that our updated width and scattering models — when implemented in the ZDM code — produces ∼10% more FRBs at redshift z = 1 than at z = 0 when compared to alternative width/scattering models, highlighting that these factors are important to understand when performing FRB population modelling.

While it is well known that galaxies are composites of many emission processes, quantifying the various contributions remains challenging. In this work, we use unsupervised machine learning based clustering algorithms to evaluate the agreement between the clustering tools and astrophysical classifications, and hence quantify the fractional contributions of star formation processes and nuclear black hole activity to the total galaxy energy budget of radio sources. We perform clustering on the multiwavelength (optical, infrared (IR), and radio) active galactic nuclei (AGN) diagnostic spaces, using the data from the G09 and G23 fields from the Galaxy and Mass Assembly (GAMA) survey, Evolutionary Map of the Universe (EMU) survey, and theWide-field Infrared Survey Explorer (WISE).We find that the statistical clustering recovers ≈90% of the star forming galaxies (SFGs) and ≈80% of the AGN. We define a new IR-radio AGN diagnostic scheme that identifies radio AGN from IR SFGs and AGN, corresponding to the KMeans cluster with approximately 90% reliability. We demonstrate the superior power of radio AGN selection in higher dimensions using a three-dimensional space composed of directly observable parameters (W1 –W2 colour,W2 magnitude, and the 1.4GHz radio flux density). This novel three dimensional diagnostic shows immense potential in radio AGN selection that is close to 90% reliable and 90% complete. We also publish a catalogue of radio sources in the EMU survey with associated probabilities for them to be active in the optical regime, through which we emphasise the philosophy of considering a galaxy to be composed of various fractions rather than a binary classification of SFGs and AGN.

We show that the flip-flop transitions in X-ray binaries (rapid cycling between different spectral states which are sometimes seen near the global state transition) show a series of analogies to the changing state phenomena (rapid changes in the emission line properties that seem to be driven by changes in the central engine) in active galactic nuclei (AGN). Specifically, (1) the timescales for the transitions scale approximately linearly with mass and (2) both phenomena occur at a few percent of the Eddington luminosity. Because most accretion physics is expected to be scale-free, it is likely that these represent two manifestations of the same phenomena. Demonstrating this would allow the use of a much wider range of observational techniques, on a much wider range of characteristic timescales, and provide a clearer pathway toward understanding these rapid transitions than is currently available. We discuss potential means to establish the connection more firmly, and to use the combination of the observational advantages of both classes of systems to develop a better understanding of the phenomenon.

We present new Hubble Space Telescope (HST) imaging of the ionised filaments in the brightest group galaxy NGC 5044, providing the first high-resolution view of such structures in a galaxy group. The filaments extend several kiloparsecs from the centre, with widths of ∼50–120 pc. Some strands are as narrow as those in cluster cores, while others are broader, consistent with the weaker confining pressure of the intragroup medium. With our limited sample, we find that the filament width (W) roughly scales with ambient pressure (P) as W ∝ P−0.4. Combining HST with molecular and MUSE observations, we measure column densities and magnetic field strengths. Equipartition magnetic fields decline from ∼40 µG near the centre to ∼20 µG at 5 kpc, about 2–3 times weaker than in clusters. Dynamical stability arguments require stronger radial magnetic fields (∼102 µG), consistent with simulations and magnetic field lines draping and flux freezing around cavities, though such high values may be difficult to reconcile with Faraday Rotation Measure limits. Turbulence and cosmic rays can also provide complementary support.

Filaments are stable against gravitational collapse, and ultraviolet imaging reveals no star formation in NGC 5044 (<10−3 M⊙ yr–1), confirming that star formation in filaments in both groups and clusters remains largely quenched. NGC 5044 hosts an ionised gas core within its Bondi radius with ne ∝ r–1 and filling factor f ≳ 3 × 10–3, that is connected to the extended filaments, suggesting a channel for gas inflow toward the black hole.

Our results show that group filaments share the same origin and stabilising mechanisms as cluster filaments, with magnetic fields and AGN feedback preserving filamentary structures with ambient pressure and dust survival as key factors for molecular gas formation and survival. Lower pressure groups favour broader, diffuse filaments with sporadic molecular clumps and less dust shielding, while higher pressure clusters host narrower strands with stronger molecular/ionised gas alignment. We predict that (i) filament widths scale with ambient pressure, (ii) filament-coincident Faraday rotation structures should appear at ≤0.1 kpc resolution, and (iii) molecular/ionised gas co-spatiality is weaker in groups than in clusters.

The Variables and Slow Transients (VAST) Survey on the Australian SKA Pathfinder (ASKAP) is designed to systematically explore the dynamic radio sky, detecting sources that vary on timescales from minutes to several years. In this paper, we present Data Release 1 of the VAST Extragalactic Survey, which targets slowly evolving synchrotron transients in the southern sky. The observations were carried out between June 2023 and May 2025, comprising 2945 images of 276 fields spanning ∼ 12300 deg2, observed at 888 MHz with a typical rms sensitivity of 0.24 mJy beam–1 and 12—20 arcsec resolution. Each field was revisited approximately every two months, yielding 10 or 11 observations per field. The VAST pipeline extracts the light curves for all the observed sources, and additional filters are implemented to improve the reliability of the resulting light curve database. The light curve database contains 0.5 million sources and 6.4 million individual measurements, publicly available through the CSIRO data access portal. An untargeted variability search yields 117 astrophysical variables, including 27 pulsars, 40 radio stars (10 newly detected at radio wavelengths), 44 active galactic nuclei, two optically identified supernovae, one supernova candidate, one brown dwarf, and two sources without multi-wavelength counterparts that are yet to be identified. This data release provides the first large-scale, high-cadence, uniform view of long-term radio variability in the extragalactic sky and lays the groundwork for future population studies of radio transients with ASKAP.

Overlapping galaxies, in which a foreground galaxy partially overlaps a background galaxy, offer a unique opportunity to measure dust attenuation, a key nuisance parameter in galaxy studies, empirically and in great detail by modelling the light of both the foreground and background galaxy and inferring the missing light in the overlapping region. However, the current catalogue of overlapping pairs is relatively limited in number compared to catalogues dedicated to individual galaxies. Expanding this catalogue is not only a necessity to facilitate further detailed dust studies beyond the few limited studies conducted thus far, but also to improve pair-to-pair variance and support automated identification through machine learning techniques. To achieve this, we utilise galaxies classified as “overlapping” from Galaxy Zoo DECaLS (GZD-1, -2, and -5), along with images from Data Release 10 (DR10) of the DESI Legacy Survey, in our individual citizen science project to classify these pairs directly using volunteers. This new catalogue will not only provide a wealth of targets for future dust studies but will also contribute to a deeper understanding of these pairs and dust as a whole.

The JADES survey recently reported the discovery of JADES-GS-z13-1-LA at z = 13, the highest redshift Lyα emitter (LAE) ever observed. This observation suggests that either the intergalactic medium (IGM) surrounding JADES-GS-z13-1-LA is highly ionised, or the galaxy’s intrinsic Lyα emission properties are extreme. We use radiative transfer simulations of reionisation that capture the distribution of ionised gas in the z = 13 IGM to investigate the implications of JADES-GS-z13-1-LA for reionisation. We find that if JADES-GS-z13-1-LA is a typical star forming galaxy (SFG) with properties characteristic of LAEs at z ∼ 6, its detection suggests that the universe is ≳ 5% ionised by z = 13. We also investigate the possibility that the extreme properties of JADES-GS-z13-1-LA are driven by an AGN. Using a simple analysis based on the fact that AGN are expected to produce more ionising photons than SFGs, we estimate that the probability that JADES-GS-z13-1-LA hosts an AGN is 71%, 42%, and 15% if the IGM is < 1%, ≈ 5% and ≈ 25% ionised, respectively. We also highlight other features in the spectrum of JADES-GS-z13-1-LA that may be indicative of AGN activity, including strong Lyα damping wing absorption extending to ∼ 1300 Å, and a possible CII*λ1335 emission line. Our findings strongly motivate dedicated follow-up observations of JADES-GS-z13-1-LA to determine whether it hosts an AGN.

Estimating the meteoroid flux density at centimetre to metre sizes is notoriously difficult. Yet it is an important endeavour, as these sizes represent the transition between small meteoroids that pose a risk to spacecraft, and the Near-Earth Objects that are relevant for planetary defense.

We present a novel automated methodology for debiasing meteor observations from multi-camera networks, applied to data from the Desert Fireball Network (DFN). Our approach utilizes the Hierarchical Equal Area isoLatitude Pixelisation (HEALPix) framework to partition the sky into equal-area pixels at 70 km altitude, enabling precise and convenient measurement of effective survey coverage and fireball counting across the network. We developed a comprehensive data processing pipeline that analyses millions of all-sky camera images to determine clear-sky conditions through automated star source detection and flux distribution analysis.

As a case study, we apply this methodology to observations of the 2015 Southern Taurid meteor shower, during which there was significant fireball activity. Processing data from 33 cameras over a three-month period (October-December 2015), we calculate an effective observation coverage of 1.58 × 1012 km2.h and identified 54 Southern Taurid fireballs from 141 validated detections. Our results are consistent with the extrapolation of previous work done on the same meteor shower at smaller sizes, when we set a ∼ 300 kg.m−3 mean meteoroid density, consistent with the cometary origin of the Taurid stream.

The HEALPix-based approach successfully automates what was previously a labor-intensive manual process, providing a scalable solution for accurate flux measurements from distributed camera networks; it is directly applicable to other meteor surveys.

It has been 10 years since the initial discovery of “Ultra-Diffuse Galaxies” (UDGs) in the Coma cluster and the revelation that large, low surface brightness galaxies may constitute a greater fraction of galaxies than first thought. This left an open question: Are UDGs something special, or just an extension of the previously known dwarf galaxy population? Seeking to answer this question, in the decade following, dedicated simulations have studied and proposed a myriad of formation pathways to create UDGs. Observations have then pushed the limits of world-class observatories to perform detailed studies of these galaxies in large numbers across the full range of environments in the local Universe. These observations stress test simulations and challenge previous galaxy formation wisdom, with UDGs posing many open puzzles beyond just their unknown formation mechanism. To provide a few pertinent examples: there is observational evidence that not all UDGs follow the standard stellar mass – halo mass relationship; there is evidence for UDGs with extraordinarily high levels of alpha enhancement; and there is evidence that some UDGs are much more globular cluster rich than other dwarfs of similar stellar mass. In this Dawes review, we undertake the task of summarising the decade of science since the discovery of UDGs. We focus on the quiescent population of UDGs and review their general properties, their proposed formation scenarios, their internal properties and their globular cluster systems. We also provide a brief conjecture on some future directions for the next decade of UDG research.

We examine how the presence of active galactic nuclei (AGN) correlates with location in large-scale cosmic structures using the Galaxy and Mass Assembly (GAMA) survey across the G09, G12, and G15 fields. Our sample contains 18 927, 9 273, and 1 148 galaxies for highly dense filaments, moderately dense tendrils, and highly underdense voids, respectively. AGN are identified among emission-line galaxies using Baldwin-Phillips-Terlevich (BPT) diagnostic diagrams based on [NII], [SII], and [OI]. We compare AGN fractions across filament, tendril, and void regions and as a function of distance from the nearest filament centreline. Our results reveal a mild excess in filaments compared to voids when using [SII]- and [NII]-based classifications, while no significant environmental dependence is found for [OI]-based classifications. Overall, we find a weak environmental trend with AGN activity, which suggests that the local environment does not always dominate AGN activity; instead, secular processes are likely to be at play. Our findings are consistent with previous studies reporting only marginal preferences for overdense environments for AGN.

We present independent imaging analyses of Event Horizon Telescope (EHT) observations of the active galactic nuclei in radio galaxy Centaurus A and quasar 3C 279 using Generative Deep learning Image Reconstruction with Closure Terms (GenDIReCT), a recently developed machine-learning framework built on conditional diffusion models that uses interferometric closure invariants as primary observables. For Centaurus A, our reconstruction reveals two prominent emission ridges ($\simeq 80\,\unicode{x03BC}$as each) along the jet sheath with a brightness ratio of $1.4\pm 0.1$ and an opening angle of $12.3\pm 0.3$ deg. For 3C 279, we identify three distinct components in the image, with the southern jet ejecta on sub-parsec scale exhibiting a proper motion of $4.6\pm 1.0\,\unicode{x03BC}$as over $\approx 5.39$ d away from the northern components, corresponding to an apparent superluminal velocity of $\simeq 10\pm 2$ times light speed. These measurements are consistent with those reported by the EHT Collaboration. The results are significant because we demonstrate that: (1) imaging from interferometric aperture synthesis data, especially in VLBI and most acutely in extremely sparse arrays like the EHT, remains a severely ill-posed and challenging inverse problem, yet closure invariants preserve robust morphological information that can strongly constrain structural features, and (2) more importantly, closure-invariant imaging largely avoids calibration systematics, thus providing a fundamentally independent view of spatial structure with very high angular resolution. The generative nature of GenDIReCT further allows us to sample and characterise clusters of plausible image solutions for each dataset. As a calibration-independent, generative imaging approach, GenDIReCT offers a robust and truly independent blind-imaging tool for current and future VLBI experiments.

Radio recombination line (RRL) maser is a useful tool to study massive star formation regions with ionized gas close to new born massive stars. Masers often show sharp line profiles and/or extreme narrow widths, and high brightness temperatures. However, RRL masers were rarely detected only in several sources. Here we report the detection of sharp line profiles of the RRL H29α, which can be interpreted as maser candidates, in two sources within W49A, a mini-starburst region in our Galaxy. These observations, conducted with high resolution (∼ 0.03″) using the Atacama Large Millimeter/sub-millimeter Array (ALMA), reveal high brightness temperatures up to ∼ 9000K for H29α emission in another two sources, which might also be regarded as maser candidates. Additionally, suggestions for efficiently identifying RRL maser candidates are also provided.

We present a detailed analysis of the Vela pulsar’s rotational behaviour using approximately 100 months of observational data spanning from September 2016 to January 2025, during which four glitches were identified. Here, we demonstrate the post-glitch recovery of these glitches within the framework of the vortex creep model. We further present the investigation of vortex residuals (the difference between observed values and those predicted by the vortex creep model) by interpreting them in the context of the vortex bending model. In addition, we report a positive correlation between the glitch magnitude and the time to the next glitch, applicable only for the large glitch events observed in the Vela pulsar. Furthermore, we estimate the braking index of the Vela pulsar to be 2.94 $\pm$ 0.55.

We present multi-wavelength observations of the nearby spiral galaxy NGC5938 (Araish) to investigate the origin of its radio emission, specifically the contribution from active galactic nucleus (AGN) activity and star formation. Using Evolutionary Map of the Universe (EMU) data, we detect extended radio emission extending outwards to the galactic axis, with a steep non-thermal spectral index (α = −1.2 ± 0.2) indicative of synchrotron radiation from an AGN jet. The jet has a physical extent of ≈ 8.2 kpc (angular length of 64″). Multi-wavelength data from The Dark Energy Camera Plane Survey 2 (DECaPS2),Wide-field Infrared Survey Explorer (WISE), and extended Roentgen Survey with an Imaging Telescope Array (eROSITA) provide further support for this interpretation. The colour-colour diagram presenting WISE infrared observations suggests the presence of dust and young stars that trace the galaxy’s disk structure. Our analysis reveals a radio jet, alongside star formation traced by infrared emission, demonstrating the complex interplay of AGN activity and star formation in this well-resolved galaxy. Intriguingly, the spatial relationship reveals the brighter X-ray emission to be largely adjacent to and enveloping the extended radio emission. This suggests that the radio jet, while extending at a significant angle to the galactic disk, is confined by the larger X-ray gas/halo, similar to other systems (i.e., ESO 295–IG022, Centaurus A) and may indicate jet collimation and channelling effects.