We present an automated search method for radio transients on the minute timescale focused on the emerging long period transients (LPTs) in image-plane radio data. The method is tuned for use with the Murchison Widefield Array (MWA) and tested on archival observations from the GaLactic and Extragalactic All-Sky MWA Extended Survey (GLEAM-X) in the 70–300 MHz range. The images are formed from model-subtracted visibilities, before applying three filters to the time series of each pixel in an image, with each filter designed to be sensitive to a different transient behaviour. Due to the nature of radio interferometry and the refraction of the fluctuating ionosphere, the vast majority of candidates at this stage are artefacts which we identify and remove using a set of flagging measures. Of the 336 final candidates, 7 were genuine transients: 1 new LPT, 1 new pulsar, and 5 known pulsars. The performance of the method is analysed by injecting modelled transient pulses into a subset of the observations and applying the method to the result.

We present the first results from the COS-EDGES survey, targeting the kinematic connection between the interstellar medium and multi-phase circumgalactic medium (CGM) in nine isolated, near-edge-on galaxies at $z\sim0.2$, each probed along its major axis by a background quasar at impact parameters of $D=13-38$ kpc. Using VLT/UVES and HST/COS quasar spectra, we analyse Mgi, Mgii, Hi, Cii, Ciii, and Ovi absorption relative to galaxy rotation curves from Keck/LRIS and Magellan/MagE spectra. We find that low ionisation absorption for 8/9 galaxies lies below the halo escape velocity, indicating bound inflow or recycling gas, while 6/9 galaxies have high ionisation gas reaching above the halo escape velocity, suggesting some unbound material. We find that at lower $D/R_{\textrm{vir}}$ ($0.12\leq D/R_{\textrm{vir}} \leq0.20$), over 80% of absorption in all ions lies on the side of systemic velocity matching disk rotation, and the optical-depth–weighted median velocity ($v_{abs}$) is consistent with the peak rotation speed. At higher $D/R_{\textrm{vir}}$ ($0.21\leq D/R_{\textrm{vir}} \leq0.31$), the kinematics diverge by ionisation state: For the low ionisation gas, the amount of co-rotating absorption remains above 80%, yet $v_{abs}$ drops to roughly 60% of the galaxy rotation speed. For the high ionisation gas (Ovi), only 60% of the absorption is consistent with co-rotation and $v_{abs}$ drops to 20% of the galaxy rotation speed. Furthermore, the velocity widths, corresponding to 50% of the total optical depth ($\Delta v_{50}$) for low ionisation gas is up to 1.8 times larger in the inner halo than at larger radii, while for Ciii and Ovi $\Delta v_{50}$ remains unchanged with distance. The 90% optical-depth width ($\Delta v_{90}$) shows a modest decline with radius for low ionisation gas but remains constant Ciii and Ovi. At high $D/{R}_{\textrm{vir}}$, both $\Delta v_{50}$ and $\Delta v_{90}$ increase with ionisation potential. These results suggest a radially dependent CGM kinematic structure: the inner halo hosts cool, dynamically broad gas tightly coupled to disk rotation, whereas beyond $\gtrsim 0.2 R_{\textrm{vir}}$, particularly traced by Ovi and Hi, the CGM shows weaker rotational alignment and lower relative velocity dispersion. Therefore, low-ionisation gas likely traces extended co-rotating gas, inflows and/or recycled accretion, while high-ionisation gas reflects a mixture of co-rotating, lagging, discrete collisionally ionised structures and volume-filling warm halo, indicating a complex kinematic stratification of the multi-phase CGM.

Second-generation circumbinary discs around evolved binary stars, such as post-Asymptotic Giant Branch (post-AGB) binaries, provide insights into poorly understood mechanisms of dust processing and disc evolution across diverse stellar environments. We present a multi-wavelength polarimetric survey of five evolved binary systems – AR Pup, HR 4049, HR 4226, U Mon, and V709 Car – using the Very Large Telescope SPHERE/ZIMPOL instrument. Post-AGB discs show significant polarimetric brightness at optical and near-IR wavelengths, often exceeding 1% of the system’s total intensity. We also measured a maximum fractional polarisation of the scattered light for AR Pup of ${\sim}$0.7 in the V-band and ${\sim}$0.55 in the I-band. To investigate wavelength-dependent polarisation, we combine the SPHERE/ZIMPOL dataset with results from previous SPHERE/IRDIS studies. This analysis reveals that post-AGB discs exhibit a grey to blue polarimetric colour in the optical and near-IR. Along with high fractional polarisation of the scattered light and polarised intensity distribution, these findings are consistent with a surface dust composition dominated by porous aggregates, reinforcing independent observational evidence for such grains in post-AGB circumbinary discs. We also find evidence of diverse disc geometries within the post-AGB sample, including arcs, asymmetries and significant variations in disc size across optical and near-IR wavelengths for some systems (U Mon, V709 Car). Combining our findings with existing multi-technique studies, we question the classification of two systems in our sample, HR 4226 and V709 Car, which were originally identified as post-AGB binaries based on their near-IR excess. On comparing post-AGB discs to circumstellar environments around AGB stars and YSOs, we found that post-AGB systems exhibit a higher degree of polarisation than single AGB stars and are comparable to the brightest protoplanetary discs around YSOs. Overall, our results reinforce the importance of polarimetric observations in probing dust properties and complex circumbinary structures. We also highlight the importance of combining multi-wavelength and multi-technique observations with advanced radiative-transfer modelling to differentiate between the various evolutionary pathways of circumbinary discs.

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.

Recently, there have been discussions about the shape of the heliopause. Some scientists question the classical form, which is close to a paraboloid. They suggest that the heliopause may have a two-jet collimated shape. While we disagree with this view of the heliopause shape, it seems likely that for stars with stronger stellar magnetic fields and those that are at rest or moving slowly through the interstellar medium, the astropause will have a two-jet collimated shape. This paper raises the question of the stability of the two-jet collimated astrosphere. Recent studies have noted the emergence of instability in the heliosheath near the axis of the heliospheric jets, linking this to the action of neutral hydrogen atoms. We note in this paper that astrospheric jets can become unstable in the presence of strong magnetic fields, even without the influence of atoms, which is unexpected. Furthermore, due to a feedback mechanism, astrospheric jets undergo self-oscillation. We investigated the development of this instability, the nature of the feedback mechanism, and the period of self-oscillation for different system parameters. Our findings provide valuable insights into the behaviour of these unique plasma structures, and they are another step towards studying the stability of two-jet collimated astrospheres.

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.

Post-asymptotic giant branch (post-AGB) stars are exquisite tracers of s-process nucleosynthesis, preserving the surface chemical signatures of their AGB evolution. The increasing chemical diversity observed among them challenges current nucleosynthesis models and motivates detailed case studies. In this study, we present a comprehensive abundance analysis of J003643.94$-$723722.1 (J003643), a single post-AGB star in the Small Magellanic Cloud (SMC). High-resolution UVES/VLT spectra analysed with E-iSpec reveal a C/O ratio of 16.21 and an $\textrm{[s/Fe]}$ = 2.09$\pm$0.20 dex. In this study, we also report the first direct detection of lead in a post-AGB star via the Pb II 5 608.853 Å line, with a derived $\textrm{[Pb/Fe]}$ = 3.18 dex. Comparison with a comprehensive and appropriate sample of post-AGB stars across the Galaxy, Large Magellanic Cloud (LMC) and SMC shows that J003643 has a relatively high C/O ratio, far exceeding the typical range of $\sim$1–3. J003643’s $\textrm{[C/Fe]}$ (1.33$\pm$0.14 dex) and $\textrm{[s/Fe]}$ (2.09$\pm$0.20 dex) are consistent with expectations from standard third dredge-up (TDU) enrichment. However, its $\textrm{[O/Fe]}$ (-0.08$\pm$0.20 dex) is significantly lower than that of the comparative sample with similar $\textrm{[C/Fe]}$ and $\textrm{[Fe/H]}$, which typically show $\textrm{[O/Fe]}$ between 0.5 and 1.0 dex. This relatively low $\textrm{[O/Fe]}$, along with an [$\alpha$/Fe]$\,\approx0$ dex of J003643, is consistent with the chemical evolution of the SMC at $\textrm{[Fe/H]}\,\approx-1$ dex, in contrast to the oxygen-enhanced Galactic and LMC trend at $\textrm{[Fe/H]}\,\approx-1$ dex. This indicates that J003643’s high C/O ratio primarily results from its intrinsic oxygen deficiency rather than from an unusually high carbon enhancement. To better understand the CNO, alpha, Fe-peak, and heavy element nucleosynthesis, we compared J003643’s abundance pattern with yields from three stellar evolutionary codes: ATON, MONASH, and FRUITY, the latter two incorporating post-processing nucleosynthesis. While these models reproduce the majority of elemental abundances, they significantly underpredict the Pb abundance, highlighting a persistent gap in our understanding of heavy element production in AGB stars. J003643 represents the second s-process enriched single post-AGB star known in the SMC, stressing the need for more such observations. Its photospheric chemistry reflects the growing chemical diversity among post-AGB stars and reinforces the complexity of AGB nucleosynthesis beyond current theoretical models.

The advent of next-generation radio telescopes is set to transform radio astronomy by producing massive data volumes that challenge traditional processing methods. Deep learning techniques have shown strong potential in automating radio analysis tasks, yet are often constrained by the limited availability of large annotated datasets. Recent progress in self-supervised learning has led to foundational radio vision models, but adapting them for new tasks typically requires coding expertise, limiting their accessibility to a broader astronomical community. Text-based AI interfaces offer a promising alternative by enabling task-specific queries and example-driven learning. In this context, large language models (LLMs), with their remarkable zero-shot capabilities, are increasingly used in scientific domains. However, deploying large-scale models remains resource-intensive, and there is a growing demand for AI systems that can reason over both visual and textual data in astronomical analysis. This study explores small-scale vision-language models (VLMs) as AI assistants for radio astronomy, combining LLM capabilities with vision transformers. We fine-tuned the LLaVA VLM on a dataset of 59k radio images from multiple surveys, enriched with 38k image-caption pairs from the literature. The fine-tuned models show clear improvements over base models in radio-specific tasks, achieving $\sim$30% F1-score gains in extended source detection, but they underperform vision-only classifiers and exhibit $\sim$20% drop on general multimodal tasks. Inclusion of caption data and LoRA fine-tuning enhances instruction following and helps recover $\sim$10% accuracy on multimodal benchmarks (e.g., ChartQA/DocVQA). This work lays the foundation for future advancements in radio VLMs, highlighting their potential and limitations, such as the need for better multimodal alignment, higher-quality datasets, and mitigation of catastrophic forgetting.

The southern early-type, young, eccentric-orbit eclipsing binary NO Puppis forms the A component of the multiple star Gaia DR3 5528147999779517568. The B component is an astrometric binary now at a separation of about 8.1 arcsec. There may be other fainter stars in this interesting but complex stellar system. We have combined several lines of evidence, including TESS data from four sectors, new ground-based BVR photometry, HARPS (ESO) and HERCULES (UCMJO) high-resolution spectra and astrometry of NO Pup. We derive a revised set of absolute parameters with increased precision. Alternative optimal curve-fitting programs were used in the analysis, allowing a wider view of modelling and parameter uncertainties. The main parameters are as follows: $M_{Aa} = 3.58 \pm 0.11$, $M_{Ab} = 1.68 \pm 0.09$ (M$_\odot$); $R_{Aa} = 2.17 \pm 0.03$, $R_{Ab} = 1.51 \pm 0.06$ (R$_\odot$), and $T_{\mathrm{e Aa}} = 13\,300 \pm 500$, $T_{\mathrm{e Ab}} = 7\,400 \pm 500$ (K). We estimate approximate masses of the wide companions, Ba and Bb, as $M_{Ba} = 2.0$ and $M_{Bb} = 1.8$ (M$_\odot$). The close binary’s orbital separation is $a= 8.51 \pm 0.05$ (R$_\odot$); its age is approximately 20 Myr and distance $172 \pm 1$ pc. The close binary’s secondary (Ab) appears to be the source of low amplitude $ {\delta}$ Scuti-type oscillations, although the form of these oscillations is irregular and unrepetitive. Analysis of the $ \lambda$ 6678 He I profile of the primary show synchronism of the mean bodily and orbital rotations. The retention of significant orbital eccentricity, in view of the closeness of the A-system components, is unexpected and poses challenges for the explanation that we discuss.

We present the discovery of two extended, low surface-brightness radio continuum sources, each consisting of a near-circular body and an extended tail of emission, nicknamed Stingray 1 (ASKAP J0129–5350) and Stingray 2 (ASKAP J0245–5642). Both are found in the direction of the Magellanic Stream (MS) and were discovered in the Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU) survey at 944 MHz. We combine the ASKAP data with low-frequency radio observations from the GaLactic and Extragalactic All-sky MWA Survey (GLEAM) to conduct a radio continuum analysis. galaxy pairs or groups, and Odd Radio Circles (ORCs). We explore both Galactic/near Galactic scenarios, including runaway or circumgalactic supernova remnants (SNRs) and parentless pulsar-wind nebulae (PWNe), and extragalactic scenarios including radio active galactic nuclei (AGNs), dying radio galaxies, galaxy clusters, galaxy pairs or groups, head-tail radio galaxies, and ORCs, as well as the possibility that the morphology is due to a chance alignment. The Stingrays exhibit non-thermal emission with spectral indices of $\alpha=-0.89\pm0.09$ for Stingray 1 and $\alpha=-1.77\pm0.06$ for Stingray 2. We find that none of the proposed scenarios can explain all of the observed properties, however we determine it most likely that their shape is caused by some kind of complex environmental interaction. The most likely scenario from the available data is that of a head-tail radio galaxy, but more data is required for a definitive classification.

Neutron stars (NSs) emitting continuous gravitational waves may be regarded as gravitational pulsars, in the sense that it could be possible to track the evolution of their rotational period with long-baseline observations of next-generation gravitational wave (GW) interferometers. Assuming that the pulsar’s electromagnetic signal is tracked and allows us to monitor the pulsar’s spin evolution, we provide a physical interpretation of the possible observed correlation between this timing solution and its gravitational counterpart, if the system is also detected in GWs. In particular, we show that next-generation detectors, such as the Einstein Telescope, could have the sensitivity to discern different models for the coupling between the superfluid and normal components of the NS and constrain the origin of timing noise (whether due to magnetospheric or internal processes). Observational confirmation of one of the proposed scenarios would therefore provide valuable information on the physics of GW emission from pulsars.

Observations of millisecond pulsars (MSPs) at low radio frequencies play an important role in understanding the Galactic pulsar population and characterising both their emission properties and the effects of the ionised interstellar medium on the received signals. To date, only a relatively small fraction of the known MSP population has been detected at frequencies below 300 MHz, and nearly all previous MSP studies at these frequencies have been conducted with northern telescopes. We present a census of MSPs in the SMART pulsar survey, covering declinations south of $+30^{\circ}$ at a centre frequency of $154\,\mathrm{MHz}$. We detected 40 MSPs, with 11 being the first published detections below $300\,\mathrm{MHz}$. For each detection, we provide coherently dedispersed full-polarimetric integrated pulse profiles and mean flux densities. We measured significant Faraday rotation measures for 25 MSPs and identified apparent phase-dependent RM variations for three MSPs. Comparison with published profiles at other frequencies supports previous studies suggesting that the pulse component separations of MSPs vary negligibly over a wide frequency range due to their compact magnetospheres. We observe that integrated pulse profiles tend to be more polarised at low frequencies, consistent with depolarisation due to superposed orthogonal polarisation modes. The results of this census will be a valuable resource for planning future MSP monitoring projects at low frequencies and will also help to improve survey simulations to forecast the detectable MSP population with SKA-Low.

The bispectrum, being sensitive to non-Gaussianity and mode coupling of cosmological fields induced by non-linear gravitational evolution, serves as a powerful probe for detecting deviations from general relativity (GR). The signatures of modified gravity in the bispectrum are even more pronounced in redshift space, where anisotropies from peculiar velocities provide unbiased information on higher-order properties of gravity. We investigate the potential of all non-zero angular multipoles $B_l^m$ of redshift space bispectrum across all possible triangle configurations to probe degenerate higher-order scalar tensor (DHOST) theory. We show that the higher-order multipoles of the bispectrum with $l=2,4,6$ are more sensitive to the modifications in gravity than the spherically averaged monopole moment $l=0$. These multipoles demonstrate remarkable sensitivity to the higher-order growth history, which varies across triangle configurations, with acute triangles generally being the most sensitive to modification in GR. The values of various multipoles exhibit opposite signs in modified gravity compared to those predicted in GR, which serves as a robust indicator of the deviation from GR. We demonstrate that, unlike $l=2$ and 4 multipoles, the $l=6$ multipoles with $m\leq 4$ are not affected by the quadratic bias and second-order tidal bias parameters, emphasising the need to leverage their capabilities in analyses. The $(l=6, m \gt 4)$ multipoles fail to capture the second-order growth, while all $l=8$ multipoles lack any independent information regarding modified gravity in both linear and nonlinear regimes.

We present a novel method to differentiate stream-like and shell-like tidal remnants of stellar systems in galactic halos using the density-based approach of the clustering algorithm AstroLink. While previous studies lean on observation, phase-space, and action-space based criteria for stream and shell determination, we introduce AstroLink’s ordered-density plot and cluster identification as a viable tool for classification. For a given data set, the AstroLink ordered-density plot reveals the density-based hierarchical clustering structure from which the resultant clusters are identified as being statistically significant overdensities. Using simulations of sub-halo disruptions in an external potential to generate samples of tidal structures, we find that the curvature of the ordered-density plot is positive for stream-like structures and negative for shell-like structures. Comparisons with more standard classification techniques reveal strong agreement on which structures typically fit into stream-like and shell-like categories. Furthermore, we investigate the properties of clustered stream and shell samples in radial phase space and energy-angle space. Given the sensitivity of stellar tidal structures to their host dark matter (DM) halos, the identification and subsequent classification of these structures provide exciting avenues of investigation in galactic evolution dynamics and DM structure formation.

We present an analysis of high-resolution ($R \sim 48\,000$) spectroscopic and photometric data of RS Sgr, a short-period Algol-type binary system. For the first time, precise spectroscopic and absolute parameters of the system have been determined. The primary component is identified as a B3 main-sequence star with an effective temperature of 19 000 K, while the secondary is classified as an A0-type star with a temperature of 9 700 K. The secondary appears to have recently evolved off the main sequence and currently fills its Roche lobe, transferring material through the inner Lagrangian point (L$_1$) to the hotter primary component. The H$_\alpha$ emission and absorption features observed in the spectra are attributed to a combination of a low-density circumprimary disk, a gas stream originating from the secondary, and a hot spot formed at the impact site on the primary. The combined analysis of spectroscopic and photometric data yields a system distance of approximately 418 pc, which is consistent with the value derived from GAIA DR3 within the uncertainty limits.

Accurate redshift measurements are essential for studying the evolution of quasi-stellar objects (QSOs) and their role in cosmic structure formation. While spectroscopic redshifts provide high precision, they are impractical for the vast number of sources detected in large-scale surveys. Photometric redshifts, derived from broadband fluxes, offer an efficient alternative, particularly when combined with machine learning techniques. In this work, we develop and evaluate a neural network model for predicting the redshifts of QSOs in the Dark Energy Spectroscopic Instrument (DESI) Early Data Release spectroscopic catalogue, using photometry from DESI, the Widefield Infrared Survey Explorer (WISE), and the Galactic Evolution Explorer (GALEX). We compare the performance of the neural network model against a k-Nearest Neighbours approach, these being the most accurate and least resource-intensive of the methods trialled herein, optimising model parameters and assessing accuracy with standard statistical metrics. Our results show that incorporating ultraviolet photometry from GALEX improves photometric redshift estimates, reducing scatter and catastrophic outliers compared to models trained only on near infrared and optical bands. The neural network achieves a correlation coefficient with spectroscopic redshift of $0.9187$ with normalised median absolute deviation of $0.197$, representing a significant improvement over other methods. Our work combines DESI, WISE, and GALEX measurements, providing robust predictions which address the difficulties in predicting photometric redshift of QSOs over a large redshift range.

We report the detection of a potential quasi-periodic signal with a period of $\sim$2 yr in the blazar ON 246, based on Fermi-LAT ($\gamma$-rays) and ASAS-SN (optical) observations spanning 11.5 yr (MJD 55932–60081). We applied various techniques to investigate periodic signatures in the light curves, including the Lomb-Scargle periodogram (LSP), weighted wavelet Z-transform (WWZ), and REDFIT. The significance of the signals detected in LSP and WWZ was assessed using two independent approaches: Monte Carlo simulations and red noise modelling. Our analysis revealed a dominant peak in the $\gamma$-ray and optical light curves, with a significance level exceeding 3$\sigma$ in both LSP and WWZ, consistently persisting throughout the observation period. Additionally, the REDFIT analysis confirmed the presence of a quasi-periodic signal at $\sim$0.00134 day$^{-1}$ with a 99$\%$ confidence threshold. To explain the observed quasi-periodic variations in $\gamma$-ray and optical emissions, we explored various potential physical mechanisms. Our analysis suggests that the detected periodicity could originate from a supermassive binary black hole (SMBBH) system or the jet-induced orbital motion within such a system. Based on variability characteristics, we estimated the black hole mass of ON 246. The study suggests that the mass lies within the range of approximately $(0.142 - 8.22) \times 10^9$ M$_{\odot}$.

We report the radio continuum detection of well-known Galactic Planetary Nebula (PN) NGC 5189, observed at 943 MHz during the Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU) survey. Two detections of NGC 5189 have been made during the survey, of better resolution than previous radio surveys. Both measurements of the integrated flux density are consistent with each other, at $S_{\rm{943\,MHz}} = 0.33\pm0.03$ Jy, and the spectral luminosity is $L_{\rm{943\,MHz}}$ = 8.89 $\times$ 10$^{13}$ W m$^{-2}$ Hz$^{-1}$. Using available flux density measurements for radio detections of NGC 5189, we calculate a radio surface brightness at 1 GHz and measure $\Sigma_{\rm1\,GHz}$ = 6.0 $\times$ 10$^{-21}$ W m$^{-2}$ Hz$^{-1}$ sr$^{-1}$, which is in the expected range for Galactic PNe. We measure an apparent size of $3\rlap{.}^\prime4\,\times\,2\rlap{.}^\prime2$ corresponding to physical diameters of 1.48 pc $\times$ 0.96 pc and combine available radio observations of NGC 5189 to estimate a spectral index of $\alpha$ = 0.12 $\pm$ 0.05. Hence, we agree with previous findings that NGC 5189 is a thermal (free–free) emitting nebula. Additional measurements of the optical depth ($\tau = 0.00246$) and electron density ($N_{e} = 138{\rm cm}^{-3}$) support our findings that NGC 5189 is optically thin at 943 MHz. Furthermore, the radio contours from the ASKAP–EMU image have been overlaid onto a Hubble Space Telescope (HST) Wide Field Camera 3 image, demonstrating that the radio morphology closely traces the optical. Notably, the contour alignment for the innermost region highlights the two envelopes of gas previously reported to be low-ionisation structures, which is considered a defining feature of post common–envelope PNe that surround a central Wolf-Rayet star.

Magnetic AB stars are known to produce periodic radio pulses by the electron cyclotron maser emission (ECME) mechanism. Only 19 such stars, known as ‘Main-sequence Radio Pulse emitters’ (MRPs), are currently known. The majority of MRPs have been discovered through targeted observation campaigns that involve carefully selecting a sample of stars that are likely to produce ECME and which can be detected by a given telescope within reasonable amount of time. These selection criteria inadvertently introduce bias in the resulting sample of MRPs, which affects subsequent investigation of the relation between ECME properties and stellar magnetospheric parameters. The alternative is to use all-sky surveys. Until now, MRP candidates obtained from surveys were identified based on their high circular polarisation ($\gtrsim 30\%$). In this paper, we introduce a complementary strategy, which does not require polarisation information. Using multi-epoch data from the Australian SKA Pathfinder (ASKAP) telescope, we identify four MRP candidates based on the variability in the total intensity light curves. Follow-up observations with the Australia Telescope Compact Array (ATCA) confirm three of them to be MRPs, thereby demonstrating the effectiveness of our strategy. With the expanded sample, we find that ECME is affected by temperature and the magnetic field strength, consistent with past results. There is, however, a degeneracy regarding how the two parameters govern the ECME luminosity for magnetic A and late-B stars (effective temperature $\lesssim 16$ kK). The current sample is also inadequate to investigate the role of stellar rotation, which has been shown to play a key role in driving incoherent radio emission.

Spectroscopic observations are essential for confirming associations, measuring kinematics, and determining stellar populations in dwarf galaxies. Here, we present Keck Cosmic Web Imager spectra for 12 MATLAS survey dwarfs. For 9, we confirm recession velocities consistent with their literature-assumed host galaxies. We propose revisions of the host galaxy associations for MATLAS-631, 1494, and 1938. For MATLAS-1494, our measured redshift reclassifies it from an ultra-diffuse galaxy candidate to a dwarf galaxy that is of smaller physical size and places it in the field. It also appears old and passive, providing a challenge to models that invoke quenching by tidal effects. Additionally, we measure stellar population estimates for 7 of the 12 galaxies, finding a ‘mixed bag’ of old quenched galaxies and those that are currently forming stars. Compared to the literature we find generally younger ages and higher metallicities. This result may help reconcile the observed offset of MATLAS survey dwarf galaxies from the universal stellar mass–metallicity relationship reported by Heesters et al. (2023).