Magnetic flux ropes (FRs) are twisted structures appearing on the sun, predominantly in the magnetically concentrated regions. These structures appear as coronal features known as filaments or prominences in Hα observations, and as sigmoids in X-ray, EUV observations. Using the continuous vector magnetic field observations from Helioseismic and Magnetic Imager onboard Solar Dynamics Observatory, we study the evolution of the magnetic fields in the active regions (ARs) to understand the conditions of twisted flux formation. While ARs emerge and evolve further, flux motions such as shearing and rotation are efficient mechanisms to form twisted flux ropes. Magnetic helicity quantifies the twisted magnetic fields and helicity injection through photosphere leads to its accumulation in the corona. Therefore, coronal helicity accumulation leads to twisted FR formation and its eruption. The magnetic helicity injection is seen to evolve distinctly in the regions of flux rope formation and eruption. The ARs that are associated with eruptive activity are observed with helicity injection predominantly with one sign over a period of a few days. The ARs that inject helicity with a changing sign are unlikely to form twisted FRs because coronal helicity during the period of one sign of injected helicity gets cancelled by the opposite sign of injection in the later period. As a result, the coronal field reconfigures from shared to potential structure. For a given AR, the upper limit of helicity that could cause a CME eruption is not yet understood, which can be the subject of future studies of ARs. Magnetic reconnection plays a crucial role in both the initiation and driving of FR eruptions after their formation. Data-driven simulations of the AR evolution provide more insights on the flux rope formation and its onset of eruption.

We have searched for new members of the young Emilkowalski asteroid family. The number of family members reached 13. We determined proper synthetic orbital elements of family members using Orbit9 software. We investigated the dynamical evolution of the young Emilkowalski asteroid family over a 5 Myr with Orbit9 software. To estimate the ages of the pairs, we used the method of simultaneous convergence of the nodes and perihelion orbits. We considered all possible pairs between asteroids of the family. In the case of the zero-drift rate of the semi-major axis due to the influence of the Yarkovsky effect, the ages of the pairs do not exceed 2 Myr. The obtained estimates of the age of pairs allow us to limit the integration interval in the study of the probabilistic evolution of asteroid family orbits to the range of 2 Myr.

Our study addresses the challenges of direct exoplanet observation by introducing an innovative technique based on numerical simulations. We developed and evaluated a method combining Lyot coronagraphy with an Interferometric Apodization by Homothety (IAH) in segmented apertures, aimed at next-generation large telescopes. Simulations conducted using a wavelength range centered around 0.5 μm with a 20% bandwidth show significant improvements in contrast and reduced angular separations. The technique demonstrates low chromaticity, maintaining almost constant contrast across the wavelength range, an advantage over traditional methods. These findings represent a breakthrough in enhancing exoplanet imaging capabilities, enabling more precise detection even at low angular separations, and emphasize the critical role of numerical simulations in designing high dynamic range space imaging techniques.

We study the relationship between the speed of coronal mass ejections (CMEs) and the height profile of the ambient magnetic field, quantified by its decay index, n(h). Our sample is composed of 15 very fast CMEs (VCME ≥ 1500 kms–1; all halo CMEs) and 22 halo CMEs below this speed limit from Solar Cycle 23. The very fast CMEs yield a high correlation of 0.81 between VCME and the slope of n(h) in a height range above the onset height of the torus instability if one extremely fast outlier, which closely followed another very fast CME, is excluded. This is consistent with the hypothesis that the torus instability plays a decisive role in CME acceleration. The whole sample yields a weaker correlation, which is still significant if events with a broad torus-stable dip in n(h) are excluded. A parametric simulation study of flux-rope eruptions from quadrupolar and two-scale bipolar source regions confirms the decelerating effect of such dips. Very fast, moderate-velocity, and confined eruptions are found.

We examine the phosphine on Venus debate using a multidimensional impact model covering scientific, social and psychological dimensions. We illustrate the results of the analysis with two spider diagrams.

This study analyzes the motion of bodies ejected from the Earth or the Moon. We studied the ejection of bodies from several points on the Earth’s surface, as well as from the most far point of the Moon from the Sun. Different velocities and angles of ejection of bodies were considered. The dynamical lifetimes of bodies reached a few hundred million years. Over the entire considered time interval, the values of the probability of a collision of a body ejected from the Earth with the Earth were approximately 0.3, 0.2, and 0.15–0.2 at an ejection velocity υej equaled to 11.5, 12, and 14 km/s, respectively. At υej≤11.3 km/s, most of the ejected bodies fell back onto the Earth. The total number of bodies delivered to the Earth and Venus probably did not differ much. The probabilities of collisions of bodies with Mercury and Mars usually did not exceed 0.1 and 0.02, respectively. At υej ≥11.5 km/s, the probability of a collision of a body ejected from the Earth with the Moon was about 15–35 times less than that with the Earth, and it was about 0.01. The probability of a collision with the Earth for a body ejected from the Moon moving in its present orbit was about 0.3–0.32, 0.2–0.22, and 0.1–0.14 at υej =2.5 km/s, υej =5 km/s, and at 12≤ υej ≤16.4 km/s, respectively.

Human civilization continues to experience rapid growth in energy consumption, while projections of population stabilization remain uncertain. A continued trajectory of exponential energy use would cause direct heating of the planet by ∼2300, which would also coincide with a transition to a Kardashev type-I civilization. If such patterns of energy consumption are typical for other technological civilizations, then the lack of evidence for extraterrestrial life suggests that Earth may be among the first. This implies that a “Great Filter” may exist in the near future, which would mark a critical juncture of whether civilization on Earth becomes spacefaring or extinct. Any extant technological civilizations are likely those that have achieved long-term equilibrium with energy consumption and population growth. The search for technosignatures by ongoing ground- and space-based observatories will provide a way to test the Great Filter hypothesis and examine the extent to which energy-intensive civilizations occur in the galaxy.

Eruptions of filaments are defined by different parameters, specially, sigmoid handedness and direction of the eruption, which are important parameters for forecasting the geoeffectiveness of consequent interplanetary coronal mass ejection (ICME) or magnetic cloud. Solar filaments often exhibit rotation and deflection during eruptions, which would significantly affect the geoeffectiveness of the coronal mass ejections (CMEs). Therefore, understanding the mechanisms that lead to such lateral displacement of filaments is a great concern to space weather forecasting. Two case studies are discussed. Firstly, the events of September 8 and September 10 2014, were analyzed from the Sun to the Earth. The numerical heliospheric simulation EUHFORIA shows that the handedness of the EUV sigmoid deduced from coronagraph observations was different from the tilt of the ICME at 1 au, suggesting a rotation of the CME in the low corona. A potential undetected low coronal rotation led to erroneous space weather prediction. The second event concerns a filament observed on August 20 2021, which underwent a rotation of 73 degrees during its eruption, implying a significant lateral drifting of the filament material. A data-constrained magnetohydrodynamic (MHD) simulation confirms such a rotation. These two studies reinforce the idea that CMEs are subjected to more significant rotation and deflection in the low corona than during their journey in the heliosphere.

The Magellanic Stream (MS), a tail of diffuse gas formed from tidal and ram pressure interactions between the Small and Large Magellanic Clouds (SMC and LMC) and the Halo of the Milky Way, is primarily composed of neutral atomic hydrogen (HI). The deficiency of dust and the diffuse nature of the present gas make molecular formation rare and difficult, but if present, could lead to regions potentially suitable for star formation, thereby allowing us to probe conditions of star formation similar to those at high redshifts. We search for $\text{HCO}^{+}$, HCN, HNC, and C$_2$H using the highest sensitivity observations of molecular absorption data from the Atacama Large Millimeter Array (ALMA) to trace these regions, comparing with HI archival data from the Galactic Arecibo L-Band Feed Array (GALFA) HI Survey and the Galactic All Sky Survey (GASS) to compare these environments in the MS to the HI column density threshold for molecular formation in the Milky Way. We also compare the line of sight locations with confirmed locations of stars, molecular hydrogen, and OI detections, though at higher sensitivities than the observations presented here.

We find no detections to a 3$\sigma$ significance, despite four sightlines having column densities surpassing the threshold for molecular formation in the diffuse regions of the Milky Way. Here we present our calculations for the upper limits of the column densities of each of these molecular absorption lines, ranging from $3 \times 10^{10}$ to $1 \times 10^{13}$ cm$^{-2}$. The non-detection of $\text{HCO}^{+}$ suggests that at least one of the following is true: (i) $X_{\text{HCO}^{+}{}, \mathrm{MS}}$ is significantly lower than the Milky Way value; (ii) that the widespread diffuse molecular gas observed by Rybarczyk (2022b, ApJ, 928, 79) in the Milky Way’s diffuse interstellar medium (ISM) does not have a direct analogue in the MS; (iii) the HI-to-$\text{H}_{2}$ transition occurs in the MS at a higher surface density in the MS than in the LMC or SMC; or (iv) molecular gas exists in the MS, but only in small, dense clumps.

This paper presents the effects of radio frequency interference (RFI) mitigation on a radio telescope’s sensitivity and beam pattern. It specifically explores the impact of subspace-projection mitigation on the phased array feed (PAF) beams of the Australian SKA Pathfinder (ASKAP) telescope. The goal is to demonstrate ASKAP’s ability to make science observations during active RFI mitigation. The target interfering signal is a self-generated clock signal from the digital receivers of ASKAP’s PAF. This signal is stationary, so we apply the mitigation projection to the beamformer weights at the beginning of the observation and hold them fixed. We suppressed the unwanted narrowband signal by 31 dB, to the noise floor of an 880 s integration on one antenna, with a typical degradation in sensitivity of just 1.5%. Sensitivity degradation over the whole 36 antenna array of 3.1% was then measured via interferometric assessment of system equivalent flux density (SEFD). These measurements are in line with theoretical calculation of noise increase using the correlation of the beam weights and RFI spatial signature. Further, degradation to the main beam’s gain is $\pm$ 0.4% on average at the half-power point, with no significant change to the gain in the first sidelobe and no variation during extended observations; also consistent with our modelling. In summary, we present the first demonstration of mitigation via spatial nulling with PAFs on a large aperture synthesis array telescope and assess impact on sensitivity and beam shape via SEFD and holography measurements. The mitigation introduces smaller changes to sensitivity than intrinsic sensitivity differences between beams, does not preclude high dynamic range imaging and, in continuum 1 MHz mode, recovers an otherwise corrupted holography beam map and usable astronomical source correlations in the RFI-affected channel.

Trends in elemental enrichment with stellar age can give us a powerful avenue to identify thus far unexplained origin sites of the elements. We investigate stellar abundance trends using the GALAH DR3 high-resolution spectroscopic dataset of 6 234 solar-type stars. Our study explores the elemental abundance [X/Fe] of sodium (Na) with stellar age. We find a pronounced enrichment in [Na/Fe] at super solar metallicity (i.e. [Fe/H] $ \gt \,0$) in the old sequence of Milky Way disc stars, a trend demanding a deeper understanding of the underlying source(s) responsible for the nucleosynthesis. This progressive [Na/Fe] enrichment at the young end of the old sequence has essential implications for Galactic archaeology. In this work, we propose a novel selection technique for separating the Milky Way’s thick and thin disc stellar populations (i.e. old and young sequences) based on the observed [Na/Fe] rise of $\sim$0.1 dex for stars around 5–8 Gyr old. We also compare our selection method to the conventional [Mg/Fe] vs. [Fe/H] selection approach, and we find that our new Na-based selection method better disentangles the overlap between young- and old-sequence disc stars at these intermediate ages. This is especially true at super solar [Fe/H], where the [Mg/Fe] vs. [Fe/H] or [$\alpha$/Fe] vs. [Fe/H] separation approaches exhibit significant overlap. This new selection method should help us better understand the history of the formation of the Milky Way disc.

Results from some recent numerical works, including ours, lend credence to the thesis that the ambient environment, that is, the magnitude of external pressure, affects the star-forming ability of clouds and filaments. In continuation with our series of papers on this subject, we explore this thesis further by developing new hydrodynamic simulations of accreting filaments confined by external pressures in the range $10^{4 -7}$ K cm$^{-3}$. Our principal findings are – (i) irrespective of linemass, filament-fragmentation generally yields spheroidal cores. The initially sub-critical filaments in low to intermediate external pressure environments form broad cores suggesting that weakly self-gravitating filaments must fragment via the collect – and- collapse mode to form broad cores. Transcritical filaments, by contrast, become susceptible to the Jeans-type instability and form pinched cores; (ii) the ambient environment bears upon the physical properties of filaments including their FWHM$_{fil}$. Only the filaments initially suffused with subsonic turbulence in Solar-Neighbourhood-like environments, however, have FWHM$_{fil}$$\sim$ 0.1 pc. In high pressure environs such filaments not only have much smaller widths, but also become severely eviscerated. On the contrary, filaments suffused with initially supersonic turbulence are typically broader; (iii) the quasi-oscillatory nature of velocity gradients must be ubiquitous along filament lengths and its magnitude generally increases with increasing pressure. The periodicity of the velocity gradients approximately matches the fragmentation lengthscale of filaments; (iv) oscillatory features of the radial component of the velocity gradient are a unreliable proxy for detecting signatures of accretion onto filaments; and (v) filaments at either extreme of external pressure are inefficient at cycling gas into the dense phase which could reconcile the corresponding inefficiency of star-formation in such environments.

Fast radio bursts (FRBs) are millisecond-duration radio waves from the Universe. Even though more than 50 physical models have been proposed, the origin and physical mechanism of FRB emissions are still unknown. The classification of FRBs is one of the primary approaches to understanding their mechanisms, but previous studies classified conventionally using only a few observational parameters, such as fluence and duration, which might be incomplete. To overcome this problem, we use an unsupervised machine-learning model, the Uniform Manifold Approximation and Projection to handle seven parameters simultaneously, including amplitude, linear temporal drift, time duration, central frequency, bandwidth, scaled energy, and fluence. We test the method for homogeneous 977 sub-bursts of FRB 20121102A detected by the Arecibo telescope. Our machine-learning analysis identified five distinct clusters, suggesting the possible existence of multiple different physical mechanisms responsible for the observed FRBs from the FRB 20121102A source. The geometry of the emission region and the propagation effect of FRB signals could also make such distinct clusters. This research will be a benchmark for future FRB classifications when dedicated radio telescopes such as the square kilometer array or Bustling Universe Radio Survey Telescope in Taiwan discover more FRBs than before.

We present new Australia Telescope Compact Array (ATCA) radio observations towards N 49, one of the brightest extragalactic supernova remnants (SNRs) located in the Large Magellanic Cloud (LMC). Our new and archival ATCA radio observations were analysed along with Chandra X-ray data. These observations show a prominent ‘bullet’ shaped feature beyond the southwestern boundary of the SNR. Both X-ray morphology and radio polarisation analysis support a physical connection of this feature to the SNR. The ‘bullet’ feature’s apparent velocity is estimated at $\sim$1 300 km s$^{-1}$, based on its distance ($\sim$10 pc) from the remnant’s geometric centre and estimated age ($\sim$7 600 yr). we estimated the radio spectral index, $\alpha= -0.55 \pm 0.03$ which is typical of middle-age SNRs. Polarisation maps created for N 49 show low to moderate levels of mean fractional polarisation estimated at 7$\pm$1% and 10$\pm$1% for 5.5 and 9 GHz, respectively. These values are noticeably larger than found in previous studies. Moreover, the mean value for the Faraday rotation of SNR N 49 from combining CABB data is 212$\pm$65 rad m$^{-2}$ and the maximum value of RM is 591$\pm$103 rad m$^{-2}$.

We present the Pilot Survey Phase 2 data release for the Wide-field ASKAP L-band Legacy All-sky Blind surveY (WALLABY), carried-out using the Australian SKA Pathfinder (ASKAP). We present 1760 H i detections (with a default spatial resolution of 30′′) from three pilot fields including the NGC 5044 and NGC 4808 groups as well as the Vela field, covering a total of $\sim 180$ deg$^2$ of the sky and spanning a redshift up to $z \simeq 0.09$. This release also includes kinematic models for over 126 spatially resolved galaxies. The observed median rms noise in the image cubes is 1.7 mJy per 30′′ beam and 18.5 kHz channel. This corresponds to a 5$\sigma$ H i column density sensitivity of $\sim 9.1\times10^{19}(1 + z)^4$ cm$^{-2}$ per 30′′ beam and $\sim 20$ km s$^{-1}$ channel and a 5$\sigma$ H i mass sensitivity of $\sim 5.5\times10^8 (D/100$ Mpc)$^{2}$ M$_{\odot}$ for point sources. Furthermore, we also present for the first time 12′′ high-resolution images (“cut-outs”) and catalogues for a sub-sample of 80 sources from the Pilot Survey Phase 2 fields. While we are able to recover sources with lower signal-to-noise ratio compared to sources in the Public Data Release 1, we do note that some data quality issues still persist, notably, flux discrepancies that are linked to the impact of side lobes associated with the dirty beams due to inadequate deconvolution. However, in spite of these limitations, the WALLABY Pilot Survey Phase 2 has already produced roughly a third of the number of HIPASS sources, making this the largest spatially resolved H i sample from a single survey to date.

We investigate the impact of relativistic SZ corrections on Planck measurements of massive galaxy clusters, finding that they have a significant impact at the $\approx$5–15% and up to $\approx$ 3$\sigma$ level. We investigate the possibility of constraining temperature directly from these SZ measurements but find that only weak constraints are possible for the most significant detections; for most clusters, an external temperature measurement is required to correctly measure integrated Compton-y. We also investigate the impact of profile shape assumptions and find that these have a small but non-negligible impact on measured Compton-y, at the $\approx$ 5% level. Informed by the results of these investigations, we recalibrate the Planck SZ observable-mass scaling relation, using the updated NPIPE data release and a larger sample of X-ray mass estimates. Along with the expected change in the high-mass end of the scaling relation, which does not impact Planck mass estimation, we also find hints of a low-mass deviation, but this requires better understanding of the selection function in order to confirm.

The Ultra Violet Imaging Telescope (UVIT) onboard India’s first dedicated multiwavelength satellite AstroSat observed a significant fraction of the sky in the ultraviolet with a spatial resolution of 1.4$^{\prime\prime}$. We present a catalogue of the point sources observed by UVIT in the far ultraviolet (FUV; 1 300–1 800 Å) and near ultraviolet (NUV; 2 000–3 000 Å). We carried out astrometry and photometry of 428 field pointings in the FUV and 54 field pointings in the NUV band, observed in 5 filter bands in each channel, respectively, covering an area of about 63 square degrees. The final catalogue contains about 102 773 sources. The limiting magnitude(AB) of the F148W band filter, that has the largest number of detections is $\sim$$21.3$. For the NUV channel, we find the limiting magnitude at around $\sim$23. We describe the final catalogue and present the results of the statistical analysis.

Contact binaries challenge contemporary stellar astrophysics with respect to their incidence, structure, and evolution. We explore these issues through a detailed study of two bright examples: S Ant and $\varepsilon$ CrA, that permit high-resolution spectroscopy at a relatively good S/N ratio. The availability of high-quality photometry, including data from the TESS satellite as well as Gaia parallaxes, allows us to apply the Russell paradigm to produce reliable up-to-date information on the physical properties of these binaries. As a result, models of their interactive evolution, such as the thermal relaxation oscillator scenario, can be examined. Mass transfer between the components is clearly evidenced, but the variability of the O’Connell effect over relatively short-time scales points to irregularities in the mass transfer or accretion processes. Our findings indicate that S Ant may evolve into an R CMa type Algol, while the low mass ratio of $\varepsilon$ CrA suggests a likely merger of its components in the not-too-distant future.

New advancements in radio data post-processing are underway within the Square Kilometre Array (SKA) precursor community, aiming to facilitate the extraction of scientific results from survey images through a semi-automated approach. Several of these developments leverage deep learning methodologies for diverse tasks, including source detection, object or morphology classification, and anomaly detection. Despite substantial progress, the full potential of these methods often remains untapped due to challenges associated with training large supervised models, particularly in the presence of small and class-unbalanced labelled datasets.

Self-supervised learning has recently established itself as a powerful methodology to deal with some of the aforementioned challenges, by directly learning a lower-dimensional representation from large samples of unlabelled data. The resulting model and data representation can then be used for data inspection and various downstream tasks if a small subset of labelled data is available.

In this work, we explored contrastive learning methods to learn suitable radio data representations by training the SimCLR model on large collections of unlabelled radio images taken from the ASKAP EMU and SARAO MeerKAT GPS surveys. The resulting models were fine-tuned over smaller labelled datasets, including annotated images from various radio surveys, and evaluated on radio source detection and classification tasks. Additionally, we employed the trained self-supervised models to extract features from radio images, which were used in an unsupervised search for objects with peculiar morphology in the ASKAP EMU pilot survey data. For all considered downstream tasks, we reported the model performance metrics and discussed the benefits brought by self-supervised pre-training, paving the way for building radio foundational models in the SKA era.

We present the Sydney Radio Star Catalogue, a new catalogue of stars detected at megahertz to gigahertz radio frequencies. It consists of 839 unique stars with 3 405 radio detections, more than doubling the previously known number of radio stars. We have included stars from large area searches for radio stars found using circular polarisation searches, cross-matching, variability searches, and proper motion searches as well as presenting hundreds of newly detected stars from our search of Australian SKA Pathfinder observations. The focus of this first version of the catalogue is on objects detected in surveys using SKA precursor and pathfinder instruments; however, we will expand this scope in future versions. The 839 objects in the Sydney Radio Star Catalogue are distributed across the whole sky and range from ultracool dwarfs to Wolf-Rayet stars. We demonstrate that the radio luminosities of cool dwarfs are lower than the radio luminosities of more evolved sub-giant and giant stars. We use X-ray detections of 530 radio stars by the eROSITA soft X-ray instrument onboard the Spectrum Roentgen Gamma spacecraft to show that almost all of the radio stars in the catalogue are over-luminous in the radio, indicating that the majority of stars at these radio frequencies are coherent radio emitters. The Sydney Radio Star Catalogue can be found in Vizier or at https://radiostars.org.