Astronomy and Astrophysics

Ambipolar diffusion is increasingly recognised as a key process in the lower solar atmosphere. Its highly non-linear behaviour has many non-intuitive aspects. We seek to (a) study 1D Cartesian ambipolar diffusion near null points; (b) characterise the non-linear eigenmodes for ambipolar diffusion; and (c) propose tests for ambipolar diffusion solvers in MHD codes. (a) We employed a direct analysi…

The interaction between the solar wind and the atmosphere of Venus leads to the formation of an induced magnetosphere, within which pronounced dawn–dusk asymmetries are observed in magnetic field pileup and ion transport. These asymmetries are known to depend on the orientation of the interplanetary magnetic field (IMF), but the underlying physical mechanisms governing this dependence remain inco…

We aim to study the radial and vertical extents of 12 CO gas, millimeter (mm) dust thermal emission and optical/near-infrared scattered light by dust in highly inclined protoplanetary disks. These parameters are indicators of radial drift and vertical settling, and essential to setting better constraints on planet formation. Additionally, we aim to provide estimates of the dynamical stellar masse…

Dual active galactic nuclei (AGNs) are expected in hierarchical galaxy evolution models, in which low-mass galaxies merge to build more massive ones. While observational evidence for dual AGNs is growing in massive galaxies, no clear detection has yet been found in the low-mass regime. We used photometry and spectroscopy from the first Euclid Quick Data Release, combined with a collection of mult…

Dust substructures observed in protoplanetary disks are commonly attributed to embedded planets; however, intrinsic gas--dust interactions can also generate complex morphologies. We performed two-dimensional, axisymmetric simulations of gas and dust that include dust back-reaction and parameterized turbulence to investigate how the streaming instability (SI) and vertical shear instability (VSI) s…

The James Webb Space Telescope (JWST) has recently discovered a population of compact red sources at z ≥ 4 known as little red dots (LRDs). They are characterized by their V-shaped continuum spectra and prominent broad Balmer emission lines. As their underlying physical nature remains debated, and direct study at high redshift is challenging, we seek to identify and characterize LRD analogues in …

Parsec-scale jets of blazars have so far been spatially resolved only in millimeter and submillimeter wavelengths, where very long baseline interferometry can be used to obtain milliarcsecond-scale images of the jets. We have attempted to spatially resolve the near-infrared emission in jet-dominated blazars for the first time. We used the VLTI-GRAVITY instrument to obtain milliarcsecond-scale nea…

The megahertz spectral-resolution atmospheric radiative-transfer model for ground-based observatories working at millimeter and submillimeter wavelengths has been improved following an observational campaign with the Atacama Pathfinder EXperiment (APEX). Atmospheric spectra were acquired under different diurnal, seasonal, and general weather conditions, followed by a careful analysis of the valid…

Mid-infrared astronomy from the ground faces critical challenges in accurately detecting and quantifying sources due to the dominant spatially and time-variable background noise. Moreover, chopping and nodding, the traditional methods for dealing with these background issues, will not be technically feasible on the next generation of extremely large telescopes. This limitation requires the develo…

Magnetically arrested disks (MADs) are highly dynamic astrophysical systems characterized by strong variability and transient phenomena such as magnetic flux eruption events. We investigated the azimuthal structure of the equatorial inner accretion flow during flux eruption events and propose a physical mechanism for the formation and outward transport of vertical magnetic flux tubes. We analyzed…

The WISE source, J141046.00+740511.2, has been recently observed from radio to γ rays. Although the optical spectrum is consistent with a BL Lacertae (BL Lac) object, the source displays unusually weak radio emission, which challenges standard interpretations. Our aim is to understand the origin of the broadband emission from J141046.00+740511.2, using a leptonic model of an extended jet. To obta…

Protostellar streamers are elongated structures that channel material from larger scale onto disks, influencing their physical and chemical evolution. The M512 protostar in Orion/Lynds 1641 hosts one of the most massive and extended streamer discovered so far, offering a unique opportunity to study these processes. We investigated the morphology, chemistry, and origin of this streamer, along with…

Very long baseline interferometry (VLBI) measurements of the sizes of compact extragalactic radio sources, jetted active galactic nuclei, provide data for probing the angular size--redshift relation, offering a classical cosmological test complementary to other distance--redshift methods. Aiming to update and extend previous studies conducted in the 1990s, we analyse a significantly expanded and …

Star clusters and emission-line nebulae are valuable probes of stellar populations and the chemical evolution of nearby galaxies. NGC 7793, the flocculent spiral in the Sculptor Group, contains a rich population of clusters and nebulae, although only a few absorption line objects have been studied spectroscopically so far. Our goal is to confirm the membership of a selected sample of cluster and …

Ultra-compact X-ray binaries (UCXBs) are a subclass of low-mass X-ray binaries (LMXBs) characterised by tight orbits and hydrogen-poor donor stars. We present a spectral and timing study in the hard X-ray band of 11 of the 20 confirmed UCXBs, based on 37 archival νs observations. Using both X-ray colours and fractional root mean square values, we show that our sample spans the hard, soft, and int…

Identifying the physical mechanisms of continuum emission in solar flares is important for improving our understanding of energy transport in the chromosphere. This requires reliable detection of enhanced continuum emission across different flare classes. This study aims to quantify the occurrence statistics and spatial and temporal characteristics of near-ultraviolet (NUV) continuum enhancements…

We present a joint cosmological analysis combining data from the satellite, the Atacama Cosmology Telescope, and the South Pole Telescope. We construct a unified likelihood that reproduces the measured temperature and polarisation power spectra by jointly modelling the cosmic microwave background (CMB) signal, Galactic and extragalactic foregrounds, and instrumental systematics across all dataset…

As planetary nebulae evolve, they fade and dissipate into the surrounding interstellar medium, which makes them harder to detect. Modern, advanced amateur equipment can help to uncover this hidden population of ancient `ghost' planetary nebulae. Via careful processing of long-integration, narrow-band imagery with modest aperture telescopes at a dark-sky site, we detected three new candidate plane…

Multi-planetary systems provide key constraints on planet formation and evolution, as their architecture encodes the dynamical history of planets formed within a common protoplanetary disc. However, the current population remains strongly biased towards compact, short-period systems, and only a limited number of such systems with measured masses and radii are known. HIP 41378 is an exceptional sy…

Coronal mass ejections (CMEs) are complex transient solar phenomena often associated with solar flares, large-scale current sheets (CS), and the formation of dense plasma structures, known as plasmoids or plasma blobs. Multiwavelength observations are required to study the properties, onset, and evolution of these structures. We studied the properties of multiple plasma blobs that are likely rela…