Papers for Wednesday, Feb 04 2026

GenASiS (General Astrophysical Simulation System) is a code being developed initially and primarily, though not exclusively, for the simulation of core-collapse supernovae on the world's leading capability supercomputers. This paper -- the second in a series -- documents capabilities for Newtonian self-gravitating fluid dynamics, including tabulated microphysical equations of state treating nuclei and nuclear matter (`baryonic matter'). Computation of the gravitational potential of a spheroid, and simulation of the gravitational collapse of dust and of an ideal fluid, provide tests of self-gravitation against known solutions. In multidimensional computations of the adiabatic collapse, bounce, and explosion of spherically symmetric pre-supernova progenitors -- which we propose become a standard benchmark for code comparisons -- we find that the explosions are prompt and remain spherically symmetric (as expected), with an average shock expansion speed and total kinetic energy that are inversely correlated with the progenitor mass at the onset of collapse and the compactness parameter.

The fundamental question of baryogenesis and the problem of matter-antimatter asymmetry motivate this study into the formation and evolution of antimatter objects in the early Universe. Hypothesize is the existence of isolated antimatter domains in a baryon-asymmetric Universe that survive until the era of first star formation ($Z \approx 20$). By assuming CPT-symmetry, the thermodynamics, mechanics, and energy dynamics of an antimatter gas cloud (composed of antihydrogen and antihelium) are treated symmetrically to their primordial matter counterparts. Analysis demonstrates the physical feasibility of the gravitational collapse process for a conservatively estimated antimatter domain ($\approx 5 \times 10^3 M_{\odot}$). The initial conditions easily satisfy the Jeans and Bonnor-Ebert mass criteria, indicating a high propensity for instability and runaway collapse. The subsequent dynamical evolution, driven by $\bar{H}_2$ cooling, is predicted to proceed identically to that of Population III star formation, leading to the formation of a dense, adiabatic anti-protostellar core. The theoretical viability of a true antistar hinges upon a critical assumption: the physical possibility of antinuclear fusion (e.g., the antiproton cycle) under extreme core conditions. Assuming this symmetry holds, the collapse is predicted to yield massive antistars ($\gtrsim 22 M_{\odot}$). This suggests that if antimatter domains formed in the early Universe, they likely underwent stellar formation. Observational constraints on the existence of these objects must rely on the detection of characteristic high-energy $\gamma$-ray or X-ray signals resulting from matter-antimatter annihilation at the domain boundaries or during mass accretion.

We examine non-singular bounce cosmology within the framework of a phantom scalar field coupled to the Gauss-Bonnet term in both non-viscous and bulk-viscous cases. Using the scale factor ansatz $\alpha(t)=\left(\frac{\alpha}{\eta}+t^2\right)^{\frac{1}{2 \eta}}$, we reconstruct the scalar field potential $V(t)$, and observe a smooth potential well centered at the bounce point. The resulting energy density, pressure, and equation-of-state parameter show NEC violation necessary for successful bounce, while viscosity controls post-bounce dynamics with a positive and smooth squared speed of sound. In contrast, for the non-viscous model, sharp divergences occur just at the bounce and continues to be negative in the expanding phase, which in turn emphasises the stabilising role of dissipative effects. The energy condition analysis indicates a temporary NEC and SEC violation in the viscous scenario, whereas its persistent violation within the non-viscous model suggests a continuous accelerated expansion. Observational viability is found through Bayesian MCMC fitting in regards to the Pantheon+ supernova data, with best-fit parameters providing a reduced chi-squared of $\chi_{red}^2 =0.995$ while the inflation observables derived from the reconstructed potential place our model predictions inside $68\%$ CL Planck 2018 confidence contours. Our findings suggest that bounce cosmologies could offer a physically reasonable and observationally acceptable alternative or pre-inflationary scenario, while highlighting the role that viscosity could play for a stable and smooth cosmological evolution.

Core-collapse supernovae (SNe) are sources of gravitational waves (GWs) produced by hydrodynamical instabilities and highly time-dependent anisotropies of the neutrino radiation. In this work we analyze both contributions to the GW signal for two state-of-the-art three-dimensional (3D) SN models computed with the Prometheus-Vertex neutrino-hydrodynamics code. In contrast to the far majority of models analyzed for GWs so far, our core-collapse simulations were started with 12.28 M_sun (18.88 M_sun) progenitors, whose final hour (7 min) of convective oxygen-shell burning was computed in 3D and featured a vigorous oxygen-neon shell merger. The corresponding large-scale asymmetries in the oxygen layer are conducive to buoyancy-aided neutrino-driven explosions. The models were continuously evolved in 3D from the pre-collapse evolution until 5.11 s (1.68 s) after the core bounce. The GW signals result from the well-known dynamical phenomena in the SN core such as prompt postshock convection, neutrino-driven convection, the standing accretion shock instability, proto-neutron star oscillations, and anisotropic ejecta expansion. They do not exhibit any new or specific features that can be unambiguously connected to the powerful pre-collapse activity in the progenitors, but we identify interesting differences compared to results in the literature. We also discuss measurement prospects by interferometers, confirming that GW signals from future Galactic SNe will be detectable with existing and next-generation experiments working in the frequency range f ~ 1-2000 Hz.

WLM is an archetypal dwarf irregular galaxy that has not experienced interactions with major Local Group galaxies within the past 8 Gyr. It has recently been shown that WLM is losing its gas due to ram pressure forces exerted by the surrounding intergalactic medium (IGM). In this work, we explore how ram pressure may also affect the WLM gas kinematics, and we show that its dynamics is especially perturbed at its outskirts, explaining the asymmetric rotation between the approaching and receding sides. Moreover, we have been able to decompose WLM in two main components, a compact one with a solid-body rotation that resembles a bar-like structure, and a more extended one with a characteristic double-horn profile suggesting an edge-on disk. The former is relatively unaffected by ram pressure while the latter has its dynamics considerably affected by ram pressure. This study shows that mass estimates of a dwarf galaxy like WLM should account for a full modeling of its dynamical components, especially accounting for its asymmetric rotation curve.

Quasi-periodic eruptions (QPEs) are recently discovered transients of unknown nature occurring near supermassive black holes, which feature bright X-ray bursts separated by hours to days. A promising model for QPEs is the star-disc collisions model, where a star repeatedly interacts with an accretion disc around a black hole, creating shocks that expel dense outflows of gas from which radiation emerges. We investigate the dynamics of the star-disc collisions, the properties of the outflows, and the resulting radiation signatures. Our study focuses on the generic case where the star remains unperturbed by the collision and the stellar crossing time through the disc is sufficiently long for shocked gas to flow around the star. We performed a three-dimensional (3D) radiation-hydrodynamics simulation of the star-disc collision. The star was modeled as a solid, spherical body, and the interaction was simulated for a small, local section of the accretion disc. We found that star-disc collisions generate a nearly paraboloidal bow shock. The heating of gas is not confined to the column of gas directly ahead of the star but also extends laterally as the shock front expands sideways while traveling with the star. As the star crosses the disc, it injects momentum preferentially along its direction of motion, leading to an asymmetric redistribution of energy and momentum. As a result, two outflows emerge on opposite sides of the disc with different properties: the forward outflow expands faster, contains more mass, carries more energy, and is about twice as luminous as the backward outflow. Our findings suggest that the asymmetry in outflow properties and luminosity arises naturally from the collision dynamics, offering a possible explanation for the alternating strong-weak flare patterns observed in several QPE sources.

We investigate the physical origin of the star formation scaling relations between the gas depletion time, the star-forming gas mass fraction, and the gas surface density, $\Sigma_{\rm gas}$, on kiloparsec scales, all of which are the key ingredients of the observed Kennicutt-Schmidt relation. To elucidate these trends, we employ an analytical framework that explicitly connects these kiloparsec-scale properties to the timescales governing the rapid, continuous ISM gas cycle on the scales of individual star-forming regions, including the formation, dispersal, and local depletion of star-forming gas. Using a suite of idealized disk galaxy simulations spanning a range of environments from dwarf and Milky Way-mass systems to a gas-rich starburst analog, we measure the timescales of the gas cycle and relate them to the dynamical and turbulent properties of the interstellar medium (ISM). We find that star-forming regions form on a timescale close to the vertical turbulent crossing time of the galactic disk, $\sim$3-30 Myr, which decreases at higher $\Sigma_{\rm gas}$ due to the increase in turbulent velocities in the ISM and the decrease in the disk thickness. In contrast, the local star formation and dispersal of such gas are set by the local conditions. Specifically, the local depletion time, $\sim$200-2000 Myr, is decreasing at higher $\Sigma_{\rm gas}$, as star-forming gas becomes denser and more efficient in forming stars. The lifetime of such gas is very short, $\sim$0.4-1 Myr, and only weakly increases with $\Sigma_{\rm gas}$. Together, our results demonstrate how the star formation properties of galaxies on kiloparsec scales emerge directly from the interplay between the galaxy-scale dynamics, ISM turbulence, and the state of star-forming gas.

Molecular gas, modest in mass yet pivotal within the cosmic inventory, regulates baryon cycling as the immediate fuel for star formation. Across most of cosmic history, its reservoir has remained elusive, with only the tip of the iceberg revealed by luminous carbon monoxide (CO) emitting galaxies. Here we report the first detections of the mean cosmic CO background across its rotational ladder at 7$\sigma$, together with ionized carbon ([CII]) at 3$\sigma$, over $0<z<4.2$. This uses tomographic clustering of diffuse broadband intensities with reference galaxies, directly probing aggregate emission in the cosmic web. From CO(1-0) we infer the total molecular gas density, $\Omega_{\rm H_2}$, finding it about twice that resolved in galaxy surveys. The global depletion time is $\sim$1 Gyr, shorter than the Hubble time, requiring sustained inflow. CO excitation links to star-formation surface density and, with depletion time, yields a super-linear Kennicutt-Schmidt law that appears universal. Together these results establish a global picture of galaxy growth fueled by a larger, short-lived molecular reservoir. The CO and [CII] detections mark a turning point for line-intensity mapping, replacing forecasts with empirical line strengths and defining sensitivity requirements for upcoming 3D experiments poised to open new windows on galaxy formation and cosmology.

The Electromagnetically Isolated Global Signal Estimation Platform (EIGSEP) is a new instrument designed to measure the global 21-cm signal from Cosmic Dawn and the Epoch of Reionization, redshifted to frequencies below 250 MHz. To reduce spectral structure in the antenna beam associated with ground scattering, EIGSEP uses a shaped bowtie antenna suspended in a canyon 100 m above the ground. We describe the current system design of EIGSEP, including the rotating antenna platform, a transmitter antenna to characterise the beam of the bowtie antenna, and auxiliary ground antennas. We then discuss the EIGSEP calibration scheme, which incorporates traditional Dicke switching in the receiver, and novel approaches that include beam mapping, beam modulation, and interferometric cross-correlation. The instrument has been deployed near Marjum Pass, Utah, for testing and initial data collection. We discuss the site characteristics and present initial field measurements.

Measuring stellar motions at the Milky Way's Galactic center (GC) provides unique insight into the dynamical processes within galactic nuclei. We present proper motion measurements for 23 SiO-maser emitting stars within 45'' of SgrA*, including four previously reported to have velocities exceeding their local escape velocities (i.e., they are "locally unbound" from the GC). Derived from 14 epochs of HST WFC3-IR observations (2010 - 2023), our measurements have a median precision of 0.038 mas/yr - up to ~100x more precise then previous constraints for some sources. By combining these proper motions with published radial velocities, we derive updated 3D velocities for the masers and find that only one is locally unbound (IRS 9; v3d = 370 +/- 1.2 km/s). Orbit integrations place the first constraints on the orbit of IRS 9, which is bound to the GC at larger radii with r_peri >= 0.100 +/- 0.005 pc and r_apo >= 5.25 +/- 0.18 pc. IRS 9's high velocity relative to stars at similar radii in the Nuclear Star Cluster makes it a candidate to have experienced a strong dynamical interaction in order to place it on its orbit. We explore the Hills mechanism as a possible origin, but binary evaporation and ejection velocity limits indicate that IRS 9 is unlikely to have experienced such an event in the past 0.4 Myr (the timescale constrained by the orbit integrations). Alternative mechanisms that could produce IRS 9 include binary supernova disruption, two-body interactions, and stellar collisions. Identifying additional stars like IRS 9 will be essential for understanding these various dynamical processes.

[Abridged] Some cosmological theories propose that the observable universe is a small part of a much larger universe in which parameters describing the low-energy laws of physics vary from region to region. How can we reasonably assess a theory that describes such a mostly unobservable universe? We propose a Bayesian method based on theory-generated probability distributions for our observations. We focus on basic principles, leaving aside concerns about practicality. (We also leave aside the measure problem, to discuss other issues.) We argue that cosmological theories can be tested by standard Bayesian updating, but we need to use theoretical predictions for "first-person" probabilities -- i.e., probabilities for our observations, accounting for all relevant selection effects. These selection effects can depend on the observer, and on time, so in principle first-person probabilities are defined for each observer-instant -- an observer at an instant of time. First-person probabilities should take into account everything the observer believes about herself and her surroundings -- i.e., her "subjective state". We advocate a "Principle of Self-Locating Indifference" (PSLI), asserting that any real observer should make predictions as if she were chosen randomly from the theoretically predicted observer-instants that share her subjective state. We believe the PSLI is intuitively very reasonable, but also argue that it maximizes the expected fraction of observers who will make correct predictions. Cosmological theories will in general predict a set of possible universes, each with a probability. To calculate first-person probabilities, we argue that each possible universe should be weighted by the number of observer-instants in the specified subjective state that it contains. We also discuss Boltzmann brains, the humans/Jovians parable of Hartle and Srednicki, and the use of "old evidence".

In this study, we present a comprehensive analysis of the structural, astrophysical, and dynamical properties of eight open clusters: NGC 559, NGC 1817, NGC 2141, NGC 7245, Ruprecht 15, Ruprecht 137, Ruprecht 142, and Ruprecht 169, using precise astrometric and photometric data from Gaia Data Release 3. By fitting the King model to the radial density profiles, we determined the structural parameters of the clusters, including core and limiting radii, which were found to range from 3.07 to 16.21 arcmin and from 9.97 to 25.97 arcmin, respectively. Fundamental astrophysical parameters were derived by fitting PARSEC isochrones to the colour-magnitude diagrams. The results show that the clusters have logarithmic ages between 7.95 and 9.34, metallicities in the range 0.007 to 0.015, and heliocentric distances between 1640 and 5203 pc. The total stellar masses of the clusters were estimated to lie between 257 and 1916 solar masses. For most of the clusters, the mass function slopes are consistent with the Salpeter initial mass function. Our dynamical analysis indicates that all clusters, except Ruprecht 15, are dynamically relaxed. In addition, the spatial distribution and the bimodal structure observed in the radial density profile of NGC 7245 provide strong evidence that this object is a binary cluster candidate. Finally, kinematic analysis and orbit integrations demonstrate that all clusters exhibit dynamical properties fully consistent with membership in the Galactic thin disc.

A population of anomalous ultra-massive white dwarfs discovered with Gaia, often referred to as the Q branch, show high (multi-Gyr) cooling delays produced by exotic physical mechanisms. They are believed to be the products of stellar mergers, but the exact origin and formation channel remain unclear. We obtained a spectroscopically complete, volume-limited sample of the Q branch region within 100 pc, and found significant differences in atmospheric composition and rotation rates as a function of tangential velocity. In particular, we discover that stellar remnants with the longest cooling delays do not show strong magnetism nor detectable short-period rotational variability, as opposed to what is generally believed for double-degenerate mergers. This indicates that either these white dwarfs arise from a formation channel with no strong magnetism induced, or that the magnetism produced from the merger dissipates over the cooling delay timescales. Our follow-up photometry has also discovered pulsations in the second and third hydrogen-dominated DAQ white dwarfs, one hotter than 15,500 K, possibly extending the boundaries of the DAV instability strip for white dwarfs with thin hydrogen layers.

We fit the multi-band light curves of 2,205 Type Ia supernovae (SNe~Ia) from the Zwicky Transient Facility DR2 with a one-zone radioactive decay model with a phenomenological addition to include Fe recombination physics. We find a strong correlation between inferred nickel mass and SALT2 stretch, which within our simplified modelling is linked to larger ejecta masses providing longer diffusion times, providing a physical basis for the brighter-slower relation. SN~Ia in low-mass hosts ($\log_{10}(M_*/M_\odot) < 10$) produce $12\%$ more $^{56}$Ni than those in high-mass hosts ($\Delta M_{\rm Ni} = 0.13~M_\odot$), linking the host-galaxy mass step to ejecta properties and hinting at metallicity or age-dependent burning efficiencies. This suggests that standardisation based on physical parameters may remove the mass-step. SN~1991T-like events show higher ejecta masses (median $1.64~M_\odot$ vs. $1.38~M_\odot$ for normals) and produce $30\%$ more $^{56}$Ni, with $84\%$ having super-Chandrasekhar masses. Through Hierarchical modelling of $902$ SNe ($z \leq 0.06$), we find thermonuclear supernovae can be well described by a Gaussian distribution in ejecta mass and nickel mass with $\mu_{\rm ej} = 1.26 \pm 0.01~M_\odot$ ($\sigma_{\rm ej} = 0.33 \pm 0.01~M_\odot$) and $\mu_{\rm Ni} = 0.64 \pm 0.06~M_\odot$ ($\sigma_{\rm Ni} = 0.42 \pm 0.02~M_\odot$), respectively. This leads to inferred fractions of $43 \pm 2\%$ sub-$M_{\rm Ch}$ ($<1.2~M_\odot$), $34 \pm 1\%$ near-$M_{\rm Ch}$ ($1.2$--$1.5~M_\odot$), and $24 \pm 2\%$ super-$M_{\rm Ch}$ ($>1.5~M_\odot$) events. This work provides a step towards holistic physical characterization of the local SN~Ia population, reinforcing the physical basis of SN~Ia standardization while quantifying diversity and environmental dependencies critical for understanding progenitor physics and mitigating systematics in precision cosmology.

We present near-infrared (NIR) spectroscopy of the hydrogen- and helium-poor (Type Ic) supernova (SN) 2024aecx that displays a strong NIR excess emerging 32 days post peak. SN 2024aecx is a peculiar SN Ic that exhibited luminous shock-cooling emission at early times, suggestive of close-in circumstellar medium (CSM), unexpected for this class of SNe. Its early NIR spectra are typical for a SN Ic but with strong CI absorption features. By ~32 days post peak, the spectra show a strong NIR excess, while maintaining normal optical colors, unprecedented for SNe Ic. We find that the NIR excess is well fit with a single-temperature, optically thin dust model with declining temperature, increasing mass, and roughly constant luminosity over time. The NIR excess appears too promptly for dust to have formed in the SN ejecta, indicating an IR echo from pre-existing dust in the CSM. The IR echo is likely powered by the relatively slowly evolving SN peak light, and not the brief shock cooling emission, as the latter requires unrealistically high CSM densities to explain the observed dust mass. We consider different potential CSM geometries and find that a thick face-on disk with an inner edge around $5\times 10^{16}$ cm can best explain the dust mass and temperature evolution. In this scenario, the SN shock should start interacting with this CSM $440\pm200$ days post explosion. CSM around SN Ic is rare, and follow-up observations of SN 2024aecx will probe the mass-loss process responsible for removing hydrogen and helium from their progenitor star.

The Sloan Digital Sky Survey-V (SDSS-V) Magellanic Genesis survey is a spectroscopic program designed to map the kinematic and chemical structure of the Magellanic Clouds using APOGEE and BOSS spectroscopy. This overview describes the survey's design, target selection, and science goals, and highlights some first results using these data. In the inner regions of the Large and Small Magellanic Clouds (LMC and SMC), the survey obtained high-resolution near-infrared APOGEE spectra (S/N~45) of ~14,000 bright, oxygen-rich asymptotic giant branch (AGB-O) stars. These data provide contiguous spatial coverage of the Clouds' main bodies, enabling detailed chemo-dynamical studies. To explore extended structures, the survey includes BOSS optical spectroscopy of fainter red giant (RG) stars selected with \gaia~DR3 data, reaching G~17.5. Many of these targets extend to the outer regions of the Clouds, which are known to span ~20 deg (LMC) and ~12 deg(SMC) and contain diffuse substructures of unclear origin. BOSS data in the inner regions also complement APOGEE by providing elements inaccessible in the near-infrared and enabling cross-calibration between instruments. The survey further includes APOGEE and BOSS observations of ~300 evolved massive stars and a small sample of symbiotic binaries previously observed by APOGEE-1 and -2, enhancing our understanding of massive stellar evolution and complementing the SDSS-V main-sequence massive star program.

Double-plane gravitational lensing is a rare but increasingly observed phenomenon in which the light from a distant source is lensed by two foreground objects at different redshifts. Such systems can be used to provide simultaneous constraints on the Hubble constant $H_0$ and the dark-energy equation of state, independent of and complementary to other probes. However, just as for single-plane gravitational lenses, the precision of these constraints is limited by the so-called mass-sheet degeneracy (MSD) -- a fundamental limit to the knowledge of the mass profiles of lens galaxies and the line of sight that can be obtained from imaging constraints alone. In this work, we show explicitly how contributions from the line of sight appear in double-plane systems. Because these contributions modify angular diameter distances, we argue that cosmological priors should not be used to simply fix the ``cosmological scaling factor'', a ratio of angular diameter distances which is key to the modelling of double-plane lenses. Motivated by this fact, we generalise the double-plane MSD to account for this uncertainty in the scaling factor. While this complicates the time-delay function, we show that, using the ``unfolding relation'', a geometric relation between distances which holds even in the presence of line-of-sight corrections, the uncertainty in the Hubble constant reduces to the familiar mass-sheet transformation of the first lens plane, and a line-of-sight contribution between the observer and the second lens plane. Our main message is therefore a prescription for reducing the degrees of freedom within double-plane models, while still safely accounting for the MSD in measurements of $H_0$.

In this work, we explore several ways to detect possible exocomet transits in the TESS (The Transiting Exoplanet Survey Satellite) light curves. The first one has been presented in our previous work, a machine learning approach based on the Random Forest algorithm. It was trained on asymmetric transit profiles calculated as a result of the modelling of a comet transit, and then applied to real star light curves from Sector 1 of TESS. This allowed us to detect 32 candidates with weak and non-periodic brightness dips that may correspond to comet-like events. The aim of this work is to analyse the events identified by the visual inspection to make sure that the features detected were not caused by instrumental effects. The second approach to detect possible exocomet transits, which is proposed, is an independent statistical method to test the results of the machine learning algorithm and to look for asymmetric minima directly in the light curves. This approach was applied to \b{eta} Pictoris light curves using TESS data from Sectors 5, 6, 32, and 33. The algorithm reproduced nearly all previously known events deeper than 0.03 % of the star flux, showing that it is efficient to detect shallow and irregular flux changes in the different sectors of the TESS data and at the different levels of noise. The combination of machine learning, visual inspection, and statistical analysis facilitates the identification of faint and short-lived asymmetric transits in photometric data. Although the number of confirmed exocomet transits is still small, the growing amount of observations points to their likely presence in many young planetary systems.

We compile a sample of 83 Little Red Dots (LRDs) with JWST imaging and find that a substantial fraction ($\sim$43%, rising to $\gtrsim$85% for the most luminous LRDs) host one or more spatially offset, UV-bright companions at projected separations of $0.5\rm \, kpc \lesssim d\lesssim 5 \rm \,kpc$, with median of $\langle d \rangle = 1.0\,\mathrm{kpc}$. This fraction is even higher when smaller spatial scales are probed at high S/N ratio: we show that the two most strongly lensed LRDs known to date, A383-LRD and the newly discovered A68-LRD, both have UV-bright companions at separations of only $d\sim0.3$ kpc, below the resolution limit of most unlensed JWST samples. We explore whether these ubiquitous red/blue configurations may be physically linked to the formation of LRDs, in analogy with the "synchronized pair" scenario originally proposed for direct-collapse black hole formation. In this picture, ultraviolet radiation from the companions, which typically have modest stellar masses ($M_\ast \sim 10^{8-9}M_\odot$), suppresses molecular hydrogen cooling in nearby gas, allowing nearly isothermal collapse and the formation of extremely compact objects, such as massive black holes or quasi-stars. Using component-resolved photometry and SED modeling, we infer Lyman-Werner radiation fields of $J_{21,LW} \sim 10^{2.5}$-$10^{5}$ at the locations of the red components, comparable to those required in direct-collapse models, suggesting that the necessary photodissociation conditions are realized in many LRD systems. This framework provides a simple and self-consistent explanation for the extreme compactness and distinctive spectral properties of LRDs, and links long-standing theoretical models for early compact object formation directly to a population now observed with JWST in the early universe.

Double-peaked H$\alpha$ emission profiles can serve as potential signatures of accreting intermediate-mass black holes (IMBHs), particularly those residing outside galactic nuclei. Such features are expected to arise from rotating disk-like structures around black holes and can be used to identify elusive IMBH candidates. \citet{Almeida2022ApJ...934..100S} reported a sample of such double-peaked H$\alpha$ sources in the MUSE-Wide survey, interpreting them as potential signatures of wandering IMBHs after systematically excluding alternative explanations. Their method relied on constructing H$\alpha$ maps around central galaxies and visually identifying compact emission clumps in the surrounding halo regions. In this work, we revisit the analysis using the deeper MUSE Extremely Deep Field (MXDF) data and an automated detection algorithm tailored to identify such features. However, we do not recover any candidate population in MXDF, resulting in a null detection. This outcome is nevertheless informative, as it (1) highlights the inherent challenges in detecting IMBHs, and (2) demonstrates the potential of automated approaches for future systematic searches, even though it did not yield a positive outcome in this case.

Understanding planetary habitability requires a comparative approach that explores the divergent evolutionary outcomes of Earth and Venus. The Habitable Worlds Observatory (HWO) will be uniquely positioned to conduct a statistical and physical census of terrestrial exoplanets spanning the Venus Zone (VZ) and the Habitable Zone (HZ), enabling the detection and atmospheric characterization of post-runaway greenhouse worlds (``exoVenuses''). We present an updated list of VZ exoplanets, which raises the number of known candidates to 370. We describe a science case and an observing strategy for VZ exoplanets that integrates precursor exoplanet detection data and stellar characterization with HWO direct imaging, spectroscopy across the UV/optical/IR, and spectropolarimetry. Our proposed framework emphasizes a pathway toward the diagnosis of sulfur chemistry (SO$_2$) and aerosol physics (H$_2$SO$_4$ clouds/hazes), planetary redox states (O$_2$/O$_3$ false positives from hydrogen loss), and cloud microphysics detection (rainbow polarization). We quantify implications for HWO requirements, including UV access to 0.2--0.4 $\mu$m, optical/NIR coverage to $\gtrsim$1.5 $\mu$m, inner working angle (IWA) reaching 0.3--1.5 AU around nearby Sun-like stars, and the SNR/resolution needed for key features. Finally, we outline a community-driven path to producing robust demographic inferences and target selection for optimizing HWO observations.

The results of spectroscopic and photometric monitoring of the classical T Tauri star RY Tau are presented. The observation series span 220 nights from 2013 to 2024. During the observation period, the star's brightness varied within the range of V=9-11 mag. The rotation axis of the "star + accretion disk" system is tilted at a large angle, so the line of sight intersects the wind region and accreting flows in the star's magnetosphere. Variability in the short-wavelength wing of the Halpha emission line and the profile of the D NaI resonance doublet are analyzed. It is shown that the wind and accretion flows vary on a time scale of approximately 20 days. When the predominant flow direction changes, a time lag is observed: initially, accretion increases, and after two days, absorption in the line-of-sight wind decreases. It is concluded that the spectral line profiles are formed in the magnetospheric accretion flows and the conical wind originating from the boundary of the star's magnetosphere. The time lag is determined by the tilt of the magnetic dipole and the opening angle of the conical wind. It is assumed that RY Tau operates in an unstable propeller mode, and fluctuations in the accretion and wind flows are caused by density waves in the accretion disk.

High-redshift quasars have been an excellent tracer to study the astrophysics and cosmology at early Universe. Using 216,949 high-redshift quasar candidates ($5.0 \leq z < 6.3$) selected via machine learning from the Legacy Survey Data Release 9 and the Wide-field Infrared Survey Explorer, we perform wide-field clustering analysis to investigate the large-scale environment of those high-redshift quasars. We construct the projected auto correlation function of those high-redshift quasars that is weighted by its predicted probability of being a true high-redshift quasar, from which we derive the bias parameter and the typical dark matter halo mass of those quasars. The dark matter halo mass of quasars estimated from the projected auto correlation function is $\log(M_h/M_{\odot})=12.2 ^{+0.2}_{-0.7}$ ($11.9^{+0.3}_{-0.7}$), with the bias parameter $b$ of $12.34 ^{+4.26}_{-4.37}$ ($11.52^{+4.02}_{-4.14}$) for the redshift interval of $5.0 \leq z <5.7$ ($5.7 \leq z <6.3$). Our results, combined with other measurements of dark matter halo masses for quasars or active galactic nucleus which obtain a lower dark matter halo mass of $\sim 10^{11.5}$ M$_\odot$ at similar redshift, suggest a more complex, and possibly non-monotonic evolution of quasar hosting dark matter halo. Moreover, we estimate the duty cycle of those quasars, which is $0.008^{+0.135}_{-0.007}$ ($0.003+^{+0.047}_{-0.003}$) for the redshift interval of $5.0 \leq z <5.7$ ($5.7 \leq z <6.3$).

Complete catalogs of molecular clouds in the Milky Way allow analysis of the molecular medium and the star formation properties of the Milky Way that closely follows the method used for nearby galaxies. We explore whether the big dip in the radial distribution of molecular gas in the Milky Way is peculiar and find several other galaxies with similar patterns, all with similar morphological classifications of YClxxGnR, indicating a clearly defined, long bar leading to a grand-design spiral. This category is fairly rare among galaxies in the PHANGS sample, but all galaxies with this classification have some evidence for dips in the radial distribution of CO emission. The lengths of the bars correlate with the extents of the dips. The Milky Way and the other galaxies with dips have similar stellar masses and star formation rates, both lying near the high ends of the distributions for all PHANGS galaxies.

Strong gravitational lensing has to deal with many modeling degeneracies, the most notable being the Mass Sheet Degeneracy (MSD). We review the MSD when one needs to model more lens planes, each one with an internal mass sheet. We take into account the non-linear lens-lens coupling and line of sight effects, the latter treated as external mass sheets with associated shear. If second order shear terms on external and internal mass sheets can be neglected, we show that the MSD is always retained, and the mass sheets influence can be reabsorbed in the redefinition of angular diameter distances. In particular, internal and external mass sheets can be placed on the same footing. The version of the MSD discussed here does not require any particular relation between the internal mass sheets in the different planes. Even when including time delays from all sources, a residual degeneracy involving time delays, mass sheets and $ H_0 $ remains. We develop a framework which shows what can actually be constrained in multiple plane lens systems.

We present four newly validated transiting brown dwarfs identified through TESS photometry and confirmed with high-precision radial velocity measurements obtained from the FEROS and PLATOSpec spectrographs. Notably, three of these companions exhibit orbital periods exceeding 100 days, thereby expanding the sample of long-period transiting brown dwarfs from two to five systems. The host stars of long-period brown dwarfs show mild subsolar metallicity. These discoveries highlight the expansion of the metal-poor, long-period distribution and help us better understand the brown dwarf desert. In our comparative analysis of eccentricity and metallicity demographics, we utilize catalogues of long-period giant planets, brown dwarfs, and low-mass stellar companions. After accounting for tidal influences, the eccentricity distribution aligns with that of low-mass stellar binaries, presenting a different profile than that observed within the giant planet population. Additionally, the metallicity of the host stars reveals a noteworthy trend: short-period transiting brown dwarfs are predominantly associated with metal-rich stars, whereas long-period brown dwarfs are more often found around metal-poor stars, demonstrating statistical similarities to low-mass stellar hosts. This trend has also been previously observed in studies of hot and cold Jupiters and points to a period-coded mixture of channels. A natural explanation is that most brown dwarfs originate from fragmentation at wider separations, with long-period systems retaining this stellar-like imprint, while only those embedded in massive, long-lived, metal-rich protoplanetary discs are efficiently delivered and stabilised to short orbits.

We present a dedicated study of CCD serial ($x$-direction) charge transfer efficiency (CTE) in ACS/WFC. Following past studies of parallel ($y$-direction) CTE, we use the serial CTE trails behind hot pixels in calibration dark frames to characterize charge trapping and release in the serial registers of the WFC detectors. Serial CTE trails are sharper and longer than parallel CTE trails. Many fewer charge traps come into play during serial pixel transfers than parallel transfers, which explains why parallel CTE is much worse than serial CTE. We find that serial CTE can cause losses of $\sim$0.005-0.02~mag in stellar photometry and shift stellar centroids by $\sim$0.01-0.035 pixels. The pixel-based algorithm in CALACS that corrects for parallel CTE losses in WFC data has been modified to include a correction for serial CTE losses. The PCTETAB reference file has also been updated to include serial CTE parameters. The pixel-based correction for serial CTE currently runs only on full-frame WFC images obtained after SM4 (May 2009). Shortly following the publication of this report, science data corrected for both parallel and serial CTE will be available in the MAST archive.

Observations of ultra-hot Jupiters offer an unprecedented opportunity to study the physics of some of the most extreme planetary atmospheres known. With exceedingly high amounts of irradiation blasting their upper atmospheres, ultra-hot Jupiters have dayside temperatures comparable to some late type stars enabling refractory metals otherwise condensed in colder planets to exist in the gas phase, all the while still maintaining comparatively cool nightsides. The ensuing intense temperature contrasts can give rise not only to strong day-to-night winds, but also to vastly different chemical and cloud properties on opposing hemispheres. With its ability to resolve spectral features that are unique to individual chemical species, high resolution spectroscopy can unambiguously disentangle atmospheric signals of exoplanetary origin, which follow a well-defined Keplerian motion, from stationary or pseudo-stationary telluric and stellar lines. Combined, the high temperature of ultra-hot Jupiters providing access to refractory metals with narrow spectral features and the ability of high-resolution spectroscopy to resolve said narrow lines provides access to a wealth of information about these atmospheres that would otherwise be unavailable at lower resolving powers or for other types of planets. In this chapter we explore some of the key physical and chemical transitions that differentiate ultra-hot Jupiters from their colder counterparts and highlight the unique opportunities arising from probing their atmospheres using high resolution spectroscopy.

The Ca ii 854.2 nm line is widely used to study the chromosphere of the Sun. In the quiet Sun, the spatially averaged line profile shows a red asymmetry and a redshift of the line center. It is known that the effect of isotopic splitting must be taken into account in the forward modeling to reproduce the observed asymmetry. So far, no numerical model could match an average observed line profile in terms of the line width and asymmetry. Our goal is to investigate how well a simulation computed with the chromospheric extension of the MURaM code (MURaM-ChE) reproduces the spatially averaged Ca ii 854.2 nm line profile. We aim to determine the contributions from the isotopic splitting versus the dynamics in the atmosphere to the resulting line width and asymmetry. We solve the radiative transfer problem three times, once considering only the most abundant isotope of calcium in the atmosphere, once taking six calcium isotopes into account, and finally using a single composite atom model. We find the forward modeled spatially and temporally averaged spectra to be in good agreement with an average observation of the quiet Sun. In order to match the observed line width, the simulated atmosphere must be sufficiently dynamic. The typical red asymmetry can only be reproduced by taking the isotopic splitting effect into account, as suggested in the literature.

This review article is based on a seminar presented at the Higgs pairs workshop 2025. Stochastic gravitational wave backgrounds can serve as probe of the diverse phenomenology encountered in beyond-Standard-Model scenarios featuring phase transitions in the early Universe. Focussing on gravitational wave production from first-order phase transitions, we present the main results of a recent analysis by the LISA Cosmology Working Group concerning the detectability of such signals with LISA. Strong degeneracies, both among the parameters controlling the phase transition and between these and the parameters of the beyond-Standard-Model scenario underlying the phase transition, complicate the reconstruction of the model from a potential signal. Nonetheless, once a specific scenario is assumed, LISA observations can supply constraints possibly complementary to those obtainable from present and future particle colliders.

The surface-brightness-color (SBC) relationship for Red Clump stars provides a critical foundation for precision distance ladder measurements, including the 1\% distance determination to the Large Magellanic Cloud. Current SBC calibrations rely on angular diameter measurements of nearby Red Clump stars obtained through long-baseline optical interferometry using the Very Large Telescope Interferometer. We explore the application of intensity interferometry to measure limb-darkened angular diameters of Red Clump stars, offering a complementary approach to traditional amplitude interferometry. We describe the framework for extracting angular diameters from squared visibility measurements in intensity interferometry, accounting for limb darkening through the stellar atmosphere models. For the Red Clump star HD~17652, we show that intensity interferometry in the $H$ band at baselines matching PIONIER ($\sim$100~m) could achieve $<1$\% angular size uncertainties in 2-hour exposures by measuring the primary peak of the visibility function, enabling direct comparison with existing measurements. Critically, observations at shorter wavelengths probe the secondary visibility maximum, providing independent checks of both measurement and systematic errors that are largely insensitive to limb-darkening assumptions. Exploiting the multiplex advantage of simultaneous multi-bandpass observations and the large number of baselines available with telescope arrays such as the Cherenkov Telescope Array Observatory can reduce observing times to practical levels, making intensity interferometry a viable tool for validating the angular sizes for a subset of the Red Clump star calibration sample.

We use rotation splittings derived from very long and long time series, namely 25.2, 12.6 and 6.3 year long, computed by Korzennik (2023) independent methodology to characterize the solar tachocline and its variation with latitude and time. We use two different inversion methodologies and a model of the tachocline to derive its position, width and the amplitude of the radial shear. To validate our methodology we present results from simulated rotational splittings, whether including or not random noise commensurable with the current observational precision. We also describe how we leverage the fact that one of our methodologies uses an initial guess that can be chosen to include a priori information. In order to try to resolve the tachocline, we increased the radial density of the inversion grid and showed how it affect the inferences. We also show how the trade off between smoothing and noise magnification affects these, as well as the effectiveness of using an informed initial guess. Results derived from high-precision rotational splittings show clearly that the location of the tachocline at low latitudes is different for its position at high latitudes. The latitudinal variation of its width is not significantly constrained, but our results agree with estimates based on forward modeling. When using splittings derived from somewhat shorter time series, we find temporal variations that are neither definitive nor significant, since we see systematic differences when using different methodologies.

We combine Gaia Data Release 3 and artificial intelligence to enhance the current statistics of substellar companions, particularly within regions of the orbital period vs. mass parameter space that remain poorly constrained by the radial velocity and transit detection methods. Using supervised learning, we train a deep neural network to recognise the characteristic distribution of the fit quality statistics corresponding to a Gaia DR3 astrometric solution for a non single star. We generate a deep learning model, ExoDNN, which predicts the probability of a DR3 source to host unresolved companions based on those fit quality statistics. Applying the predictive capability of ExoDNN to a volume limited sample of F,G,K and M stars from Gaia DR3, we have produced a list of 7414 candidate stars hosting companions. The stellar properties of these candidates, such as their mass and metallicity, are similar to those of the Gaia DR3 non single star sample. We also identify synergies with future observatories, such as PLATO, and we propose a follow up strategy with the intention of investigating the most promising candidates among those samples.

Massive stars have been proposed as candidates to be major factories of Galactic cosmic rays (GCRs).However, this claim lacks enough empirical evidence, especially for isolated this http URL powerful stellar winds from massive stars impact the ambient medium producing strong shocks suitable for accelerating relativistic this http URL detection of non-thermal emission-particularly synchrotron emission in low radio frequencies-serves as a key proof of particle acceleration this http URL aim to assess the potential of isolated massive stars as sources of this http URL observed the Wolf-Rayet bubble, NGC 2359, using the upgraded Giant Metrewave Radio Telescope at Band 3 (250-500 MHz) and Band 4 (550-950 MHz).Additionally, we used complementary archival radio datasets at different frequencies to derive the broad spectral energy distribution (SED) for several regions within the this http URL further characterize the interaction between the stellar wind and the ambient medium, we introduced a composite SED model including synchrotron and free-free emission, and two low-frequency turnover processes, the Razin-Tsytovich (RT) effect and free-free absorption (FFA).We used a Bayesian inference approach to fit the SEDs and constrain the electron number density and magnetic field this http URL SEDs of several regions reveal spectral indices steeper than -0.5, indicative of synchrotron emission. and show a turnover below ~1 this http URL SED modelling suggests that the observed turnover is primarily caused by the RT effect, with a minor contribution from internal this http URL analysis confirms the presence of synchrotron radiation within NGC this http URL is the second detection of non-thermal emission in a stellar bubble surrounding a WR star, reinforcing the idea that such environments are sites of relativistic particle acceleration and supporting the hypothesis that isolated massive stars are sources of GCRs of at least GeV energies.

Reliable nebular emission line diagnostics are essential for accurately inferring the physical properties (e.g. electron temperature, density, pressure, and metallicity) of H II regions from spectra. When interpreting spectra, it is typical to adopt a single zone model, e.g. at fixed density, pressure, or temperature, to infer H II region properties. However, such an assumption may not fully capture the complexities of a turbulent interstellar medium. To understand how a complex density field driven by supersonic turbulence impacts nebular emission lines, we simulate 3D H II regions surrounding a single O star, both with and without supersonic turbulence. We find that turbulence directly impacts the values of common strong line ratios. For example turbulent H II regions exhibit systematically higher [N II]/H$\alpha$, lower [O III]/H$\beta$, and lower O32, compared to homogeneous H II regions with the same mean density and ionizing source. These biases can impact inferences of metallicity, ionization parameter, excitation, and ionization source. For our choice of turbulence, direct $T_e$ method metallicity inferences are biased low, by up to 0.1 dex, which is important for metallicity studies, but not enough to explain the abundance discrepancy problem. Finally, we show that large differences between measured electron densities emerge between infrared, optical, and UV density indicators. Our results motivate the need for large grids of turbulent H II regions models that span the range of conditions seen at both high and low redshift to better interpret observed spectra.

We present a cosmological zoom-in radiation magneto-hydrodynamic (RMHD) simulation, using FORGE'd in FIRE, that follows the formation, growth, and evolution of a single metal-free Pop. III (proto)star at redshift $z \sim 14$. The simulation captures a rotationally supported circumstellar disk and protostellar jets, both resolved down to $<100$ au scales. We find the star grows to $\sim 27$ M$_{\odot}$ over $31,000$ years, with its final mass regulated by accretion and protostellar jets. Protostellar jets form because the magnetic mass-to-flux ratio lies within the regime that allows jet launching, and they are further enabled by a rotating circumstellar disk with sufficient gas-magnetic-field coupling, both present in this simulation. These jets regulate accretion onto the (proto)star and drive outflows that collide with infalling gas, slowing inflow at large radii due to the substantial momentum they carry. A circumstellar disk forms, extending out to $\sim 0.01$ pc, which remains gravitationally stable (Q $\gg 1$). The stability of the disk is maintained through both thermal support and turbulence. In this paper we focus on how jets play a critical role not only in shaping the final masses of Pop. III stars but also in directly influencing their surroundings by regulating accretion. These results will provide important insights into the initial mass function and feedback processes in the earliest star-forming regions of the Universe.

Line-Intensity Mapping (LIM) has emerged as a powerful technique for studying large-scale structure and the high-redshift universe, enabling three-dimensional maps of line emission across vast cosmological volumes. In this review, we summarize the LIM framework, its key scientific goals, and its future prospects. We describe the landscape of emission line tracers, theoretical modeling approaches, anticipated signals, and data-analysis methodologies. We also discuss experimental challenges, particularly those posed by astrophysical foregrounds, and review possible mitigation strategies. Further, we highlight a range of cross-correlation science cases, linking LIM with other cosmological surveys. Finally, we summarize current and upcoming experiments and early results, including recent first detections, while outlining the outlook for future discoveries. Specifically, LIM may offer new insights into galaxy formation and evolution and cosmology, while revealing the Epoch of Reionization, Cosmic Dawn, and possibly the Cosmic Dark Ages. LIM enables cosmological measurements that complement other probes and provide unique access to the high-redshift universe, potentially shedding light on dark matter, dark energy, and cosmic inflation.

We present a deep photometric study of the globular cluster NGC 5466 and its tidal stream using Subaru/Hyper Suprime-Cam (HSC) imaging with the metallicity-sensitive narrowband filter NB395. We develop an improved member-selection technique based on a k-nearest neighbor algorithm applied to the color-color-magnitude diagram (CCMD), enabling reliable candidate identification down to $i_{2,0} < 23.5$. Photometric metallicities derived from NB395 colors agree with previous measurements, supporting the robustness of our calibration. While modest residual contamination and possible offsets - potentially driven by variations in light-element abundances - may remain beyond 10 arcmin, the metallicity distribution of high-probability inner members matches the known mean metallicity of NGC 5466, demonstrating the effectiveness of our method. The spatial distribution of NB395-selected stars clearly delineates the tidal stream. Beyond the tidal radius, the azimuthally averaged radial surface density profile follows a power law with slope $\alpha = -4.53_{-0.14}^{+0.13}$. We also detect a power-law component perpendicular to the stream, suggestive of multiple apogalactic passages. A density gap is identified at a projected distance of $\sim200$ pc from the cluster center, consistent with eTidal N-body predictions and possibly associated with a recent pericentric passage or Galactic disk interaction. Analysis of the main-sequence mass function reveals a strong negative radial gradient in the slope within the tidal radius, whereas the slope along the outer stream is relatively flat, consistent with preferential tidal stripping of low-mass stars. These results highlight the power of HSC/NB395 photometry for identifying metal-poor populations and deriving photometric metallicities, underscoring its value for future wide-field surveys.

We report a revised spectroscopic redshift for the dusty massive galaxy S1, previously inferred with an exceptionally high baryon-to-star conversion efficiency from NIRCam slitless grism data at $z_{\rm grism}=5.58$. Our new JWST/NIRSpec IFU observations reveal multiple rest-frame optical and NIR emission lines, yielding a secure spectroscopic redshift of $z_{\rm spec}=3.2439\pm0.0002$. We show that the earlier grism-based redshift resulted from contamination by a nearby galaxy whose dispersed spectral trace overlaps with S1, illustrating a known challenge of slitless spectroscopy when only a single dispersion angle and single emission feature are available. In addition, we present new ALMA 1 mm observations, which robustly detect dust emission ($S_{\rm 1mm}=0.99\pm0.03$ mJy) and show a dust half-light radius ($R_{\rm e,1mm}=0.73\pm0.10$ kpc) slightly smaller than the stellar size ($R_{\rm e, F444W} = 0.97\pm0.01$ kpc). Using the revised redshift and compiled multi-wavelength photometry, we update the UV-to-FIR SED and find that S1 is less extreme than previously inferred, yet remains a very massive (log$M_{\star}/M_{\odot}\sim10.6$), heavily obscured star-forming galaxy. The updated SED modeling reveals S1 to be a very dust- and gas-rich system with a moderate star formation rate and a long gas depletion time ($\tau_{\rm dep} \sim 1.4$ Gyr), deviating from SMGs and OFGs, but more closely resembling typical massive main-sequence galaxies. We note that, although this revision reduces the number of ultra-massive galaxies reported in Xiao et al. 2024, it does not alter the main conclusions of that work. Overall, our study clarifies the nature of S1 and underscores the importance of multi-line spectroscopic confirmation, slitless observations at multiple position angles, and IFU data for robust redshift and physical characterization of rare massive galaxies in the early Universe.

We investigated how Gamma-Ray Burst (GRB) prompt emission measurements are affected by increasing distance to the source. We selected a sample of 26 bright GRBs with measured redshifts $z<1$ observed by the Burst Alert Telescope (BAT) on board the Neil Gehrels Swift Observatory (Swift) and simulated what BAT would have observed if the GRBs were at larger redshifts. We measured the durations of the simulated gamma-ray signals using a Bayesian block approach and calculated the enclosed fluences and peak fluxes. As expected, we found that almost all durations (fluences) measured for simulated high-$z$ GRBs were shorter (less) than their true durations (energies) due to low signal-to-noise ratio emission becoming completely dominated by background, i.e., the ``tip-of-the-iceberg'' effect. This effect strongly depends on the profile and intensity of the source light curve. Due to the uniqueness of GRB light curves, there is no common behavior in the evolution of measured durations with redshift. We compared our synthetic high-$z$ (i.e., $z>3$) GRBs to a sample of 72 observed high-$z$ bursts and found that the two samples were not inconsistent with being drawn from the same underlying population. We conclude that: (i) prompt emission durations (fluences) of high-$z$ GRBs observed by Swift/BAT are most likely underestimations, sometimes by factors of $\sim$several tens ($\sim2$), and (ii) changes in the average GRB prompt emission duration and fluence with increasing redshift are consistent with the tip-of-the-iceberg effect.

Anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) are believed to be manifestations of magnetars. Typically, AXPs exhibit higher X-ray luminosities, whereas SGRs are generally fainter and display significantly high signal-to-noise ratios only during their outburst phases. In this work, we report the long-term timing evolution of four AXPs: 1E 2259+586, 4U 0142+61, 1RXS J170849.0-400910 and 1E 1841-045, which were regularly monitored with NICER from 2017 to 2024. Over this period, we identify a total of 10 timing events. In addition to one glitch and one anti-glitch in 1E 2259+586 reported in literature, we detect another 8 new timing events: 5 glitches, 2 anti-glitches, and 1 unusual state transition event. Notably, both anti-glitches were observed in 4U 0142+61, making it the most frequent source of such events, and there is a hint of regular evolution in its pulse profile. In the case of 1RXS J170849.0-400910, it continues to exhibit pronounced high-frequency timing anomalies and undergoes a state transition event. Finally, we study the evolution of the pulse profiles and find that the profiles of 1E 2259+586 and 4U 0142+61 both evolve. This is consistent with the earlier finding that pulse profile evolution is a generic feature of magnetars.

Cluster environments influence galaxy evolution by curtailing star formation activity, notably through ram-pressure stripping (RPS). In this study, using spatially resolved spectroscopic data from the SAMI Galaxy Survey, we identify galaxies undergoing or recently affected by RPS in eight nearby clusters ($0.029 < z < 0.058$), through a visual classification scheme based on the ionised gas ($\rm H\alpha + [NII]\lambda 6584$) morphologies, split into unperturbed, asymmetric, and truncated. The projected phase-space analysis shows that asymmetric galaxies are found in a narrow region in cluster-centric distance ($\rm 0.1 < R/R_{200} < 0.6$) and have a larger dispersion in line-of-sight velocity ($\sigma(|v_{pec}|)_\mathrm{Asym} = 0.71^{+0.09}_{-0.07}\ \sigma_{200}$) compared to the truncated and unperturbed samples. In terms of star formation activity, RPS candidates yield a much steeper resolved star-forming main sequence (rSFMS; $\Sigma_\mathrm{SFR} - \Sigma_\ast$) relation compared to the unperturbed counterparts, primarily emerging from having lower $\Sigma_\mathrm{SFR}$ values for the low mass density regime, with the steepest gradient deriving from the truncated sample. Moreover, radial star formation profiles reveal that star formation in RPS candidates is suppressed in the outskirts relative to unperturbed galaxies and is more prominent for the truncated sample. In contrast, central ($\rm r/r_{eff}<0.5$) star formation activity in RPS candidates is comparable with that in their unperturbed and field counterparts, suggesting no elevated activity. Taken together, this suggests an evolutionary trend linked to the RPS stage, where unperturbed galaxies likely represent recently accreted systems (pre-RPS), while asymmetric and truncated galaxies may correspond to populations undergoing RPS and post-RPS phases, respectively, favouring outside-in quenching.

General Relativity (GR) faces challenges from cosmic acceleration and observational tensions, necessitating stringent tests at cosmological scales. In this work, we probe GR deviations via a $\mu$-$\Sigma$ modified gravity parameterization, integrating KiDS-Legacy weak lensing (1347 deg$^2$, $z\leq 2.0$), joint CMB data (Planck/ACT/SPT), DESI DR2 BAO, and DES-Dovekie supernovae. KiDS-Legacy significantly improves constraint precision: $\mu_0$ (matter clustering) by $\sim 43\%$ and $\Sigma_0$ (gravitational light deflection) by $\sim 60\%$ relative to CMB alone. In the $\Lambda$CDM background, $\mu_0 = 0.21\pm 0.21$ is consistent with GR, while $\Sigma_0 = 0.149\pm 0.051$ deviates from GR at the 3.0$\sigma$ level -- attributed to large-scale CMB lensing from ACT/SPT. This precise separation of GR-consistent matter clustering and deviant light deflection provides key observational clues for new physics or data systematics. Our work underscores the critical role of synergizing high-precision CMB and WL data in advancing GR tests.

The outer Galaxy (galactocentric distance $\gtrsim$13.5 kpc) serves as an excellent laboratory for investigating the chemical complexity in low-metallicity environments. Here, we present the chemical analyses for the outer Galactic hot core Sh 2-283-1a SMM1 ($D_\mathrm{GC}$ = 15.7 kpc and $Z$ $\sim$0.3 $Z_\odot$), recently detected by Ikeda et al. (2025) using ALMA. Toward this source, a variety of molecular species, including complex organic molecules (COMs: CH$_3$OH, $^{13}$CH$_3$OH, CH$_2$DOH, and CH$_3$OCH$_3$) are detected. The molecular abundances relative to CH$_3$OH are similar to those of another outer Galactic hot core, demonstrating that chemically rich hot cores exist in different regions of the outer Galaxy. We also compared molecular abundances among hot cores in the inner Galaxy, outer Galaxy, and Magellanic Clouds. This comparison revealed that the metallicity-corrected $N$(SO$_2$)/$N$(H$_2$) ratios of outer Galactic hot cores are significantly lower than those of the inner Galactic ones, while their $N$(CH$_3$OH)/$N$(H$_2$) ratios are similar. The Magellanic hot cores show different trends despite having metallicities similar to those of the outer Galaxy, indicating that the chemical complexity of hot cores is governed by environmental conditions (e.g., cosmic ray intensity and dust temperature) rather than simple metallicity scaling. These environmental differences would also affect the production efficiency of COMs derived from CH$_3$OH, as the $N$(CH$_3$OCH$_3$)/$N$(CH$_3$OH) and $N$(C$_2$H$_5$OH)/$N$(CH$_3$OH) ratios in the outer Galactic sources are moderately lower than those of inner Galactic sources. The $N$(CH$_2$DOH)/$N$(CH$_3$OH) ratio of Sh 2-283-1a SMM1 is 1.5$^{+3.9}_{-1.2}$$\%$, comparable to that of inner Galactic high-mass sources.

We report on the periodic flux variations in the 6.7 GHz $\mathrm{CH_3OH}$ maser associated with the high-mass protostar G353.273+0.641, based on 13 yr of monitoring mainly by the Hitachi 32 m telescope. We identified a periodicity of 309 days based on a nearly complete light curve, with 833 epochs every few days. A strong correlation is found between the maser and the mid-infrared fluxes at 3.4 and 4.6 $\mu$m observed by NEOWISE during these periods, suggesting that the maser emission responds to variations in the protostellar luminosity. The average profile of the maser light curve is asymmetric and shows a steep drop in intensity just before the brightening, resembling that of some pulsating variable stars. Assuming a protostellar pulsation as the origin of maser periodicity, the observed period implies a cool and highly bloated, red supergiant-like structure. Such a bloated structure is consistent with a theoretical model of protostellar evolution under high accretion rates. The inferred protostellar parameters are broadly consistent with the theoretical model of pulsational instability during the early phase of high-mass star formation. However, a periodic accretion scenario caused by an unresolved compact protobinary cannot be completely ruled out. Several irregular peaks that deviate from the periodicity may result from episodic accretion phenomena or jet-launching events independent of the protostellar pulsation. Extremely high-resolution imaging with next-generation interferometers such as the ngVLA will provide a conclusive test for both the protostellar pulsation and the binary accretion scenarios.

Stars with masses between roughly 1 and 8~$M_\odot$ end their lives on the asymptotic giant branch (AGB), when intense mass loss takes place. The outflows are generally accepted to be driven by radiation pressure acting on dust grains that form in the dense extended atmospheres created by the action of convection and stellar pulsations. The complex physics underlying convection, stellar pulsations, and dust nucleation precludes predicting AGB mass loss from first principles. We investigated the evolution of two lobes observed to be expanding away from the AGB star Mira~A using images of polarized light obtained at six epochs using SPHERE on the VLT and of molecular emission at two epochs obtained with ALMA. While dust seems confined to the edges of the lobes, gas fills the lobes and displays higher densities than expected at the observed radii based on the large-scale mass-loss rate of Mira~A, with a total gas mass in the lobes of $\sim 2 \times 10^{-5}~M_\odot$. We find the expansion of the lobes to be consistent with both a constant velocity (ejection time in 2010 or 2011) or a decelerating expansion (ejection time in 2012). If ejection events with a similar magnitude happen periodically, we derive periods between 50 and 200~years to account for the mass-loss rate of Mira~A. This periodicity is uncertain because the average mass-loss rate of Mira A on larger scales is uncertain. We find abundances in the lobes of $\sim 1.5 \times 10^{-6}$ and $\sim 2.5 \times 10^{-6}$ for SO and SO$_2$, respectively, and of $2\times10^{-10}$, $6.5\times10^{-10}$, and $4\times10^{-7}$ for AlO, AlF, and PO. The strong variation in brightness of the different features identified in the polarized-light images is puzzling. We suggest that an asymmetric stellar radiation field preferentially illuminates specific regions of the circumstellar envelope at a given time, producing a lighthouse-like effect.

We present SQUIDPOL, a low-cost, multi-channel optical imaging polarimeter that performs simultaneous linear polarization measurements using a rotating half-wave plate, a non-polarizing beam splitter, and four wire-grid filters. We show that the off-the-shelf non-polarizing beam splitter introduces measurable polarization-dependent systematics, which can bias polarimetric measurements if left uncorrected. We quantify this effect for both transmitted and reflected beams and incorporate a correction scheme into the data-analysis pipeline. On-sky validation demonstrates stable and reproducible performance, achieving a polarization accuracy of about 0.15 percent for bright polarized standard stars. Mounted on the 60-cm Ritchey-Chretien telescope (focal length 4200 mm, f/7) at the Pyeongchang Observatory of Seoul National University, SQUIDPOL provides an effective common field of view of 13.5 by 8.2 arcminutes with a pixel scale of 0.45 arcseconds per pixel and supports standard B, V, R_C, and I_C filters.

Identifying mergers from observational data has been a crucial aspect of studying galaxy evolution and formation. Tidal features, typically fainter than 26 ${\rm mag\,arcsec^{-2}}$, exhibit a diverse range of appearances depending on the merger characteristics and are expected to be investigated in greater detail with the Rubin Observatory Large Synoptic Survey Telescope (LSST), which will reveal the low surface brightness universe with unprecedented precision. Our goal is to assess the feasibility of developing a convolutional neural network (CNN) that can distinguish between mergers and non-mergers based on LSST-like deep images. To this end, we used Illustris TNG50, one of the highest-resolution cosmological hydrodynamic simulations to date, allowing us to generate LSST-like mock images with a depth $\sim$ 29 ${\rm mag\,arcsec^{-2}}$ for low-redshift ($z=0.16$) galaxies, with labeling based on their merger status as ground truth. We focused on 151 Milky Way-like galaxies in field environments, comprising 81 non-mergers and 70 mergers. After applying data augmentation and hyperparameter tuning, a CNN model was developed with an accuracy of 65--67\%. Through additional image processing, the model was further optimized, achieving an accuracy of 67--70\% when trained on images containing only faint features. This represents an improvement of $\sim$ 5\% compared to training on images with bright features only. This suggests that faint tidal features can serve as effective indicators for distinguishing between mergers and non-mergers. The future direction for further improvement based on this study is also discussed.

The 21 cm intensity mapping provides a promising probe of the large-scale structure. Astrophysical foregrounds, as the main source of contamination to the cosmological 21 cm signal, persist in a wedge-like region of Fourier space due to the inherent chromaticity in radio interferometric observations. The foreground avoidance strategy focuses on utilizing data from relatively clean regions with minimal foreground leakage, at the cost of losing large-scale information. Non-linear structure formation, however, couples Fourier modes across scales, leaving imprints of the missing large-scale modes in the remaining data. In this work, we employ a deep learning approach to test whether large-scale features of the 21 cm brightness temperature fields, particularly the baryon acoustic oscillations (BAO), can be recovered at the field level using only short-wavelength modes that are beyond the linear scales. To explicitly assess the dependence on the training cosmology, we train the network exclusively on de-wiggled simulations, providing a controlled test of whether the reconstruction arises from physical non-linear mode coupling rather than implicit encoding of BAO features. In the ideal noise-free case, the amplitude and phase of the lost modes can be restored with high fidelity. With instrumental noise included, the reconstructed amplitude becomes biased, while the phase information remains robust. The trained network also exhibits reasonable robustness to variations in the underlying cosmological model. Together, these results suggest that mode restoration offers a complementary approach for extracting cosmological information from future 21 cm intensity mapping analyses.

We explore the potential of cross-correlating galaxies and peculiar velocities on non-linear scales to enhance cosmological constraints. Leveraging the \textsc{AbacusSummit} simulation suite and the halo occupation distribution (HOD) formalism, we train emulator models to describe the non-linear clustering of galaxies and velocities in redshift space. Our analysis demonstrates that combining galaxy and peculiar velocity clustering, provides tighter constraints on both HOD and cosmological parameters, particularly on $\sigma_8$ and $w_0$. We further apply our models to realistic mock catalogues, reproducing the expected density and peculiar velocity errors of type-Ia supernovae and Tully-Fisher/fundamental plane measurements for the combined ZTF and DESI measurements. While systematic biases arise in the HOD parameters, the cosmological constraints remain unbiased, yielding $3.8\%$ precision measurement on $f\sigma_8$ compared to $4.7\%$ using galaxy clustering alone. We demonstrate that, while combining tracers with realistic velocity measurements still yields improvement, the gains are diminished, highlighting the need for further efforts to reduce velocity measurement uncertainties and correct observational systematics on small scales.

Circumstellar discs, and especially their inner regions, covering ranges from <1 au to a few astronomical units, are the birthplaces of terrestrial planets. The inner regions are thought to be similarly diverse in structure as the well-observed outer regions probed by ALMA. Combining data and results from previous studies of the VLTI/PIONIER and VLTI/GRAVITY instruments with new, multi-epoch VLTI/MATISSE observations, we aim to provide a comprehensive picture of the structure of the inner regions of the circumstellar disc around the F-type Herbig Ae/Be star HD 142527 A, the primary of a binary star system. We model the multi-wavelength interferometric data using a parametrised, geometrically thin disc model, allowing for azimuthal asymmetry, exploring a first-order disc modulation and an off-centre Gaussian component. We find time-variable structures in the N-band observables, which we reproduce with time-dependent models. This variability manifests as azimuthally asymmetric emission, evidenced by strong, non-zero closure phases in the N-band data. Fits to individual epochs of the N-band observations yield better $\chi^2_\text{r}$ values than fits to all epochs simultaneously. This suggests substantial changes in the geometry of the inner disc emission from ~1 au up to a few astronomical-unit scales from one year to the next. Moreover, our models produce a very close-in inner disc rim $R_\text{rim}\approx0.1$ au. All together, we find a very complex, substantially non-point symmetric and temporally-variable disc ($r_\text{out}\lesssim6$ au) around the primary. The very close-in inner rim indicates the presence of material inside the typical wall-like sublimation radius $R_\text{rim,literature}\approx0.3$ au. The complex, temporally variable inner-disc geometry is likely affected or even caused by the close passing (~5 au) and short orbit ($P\approx24$ yr) of the companion HD 142527 B.

The dynamics of the inner regions of young stellar objects (YSOs) is driven by a variety of physical phenomena, from magnetospheres and accretion to the dust sublimation rim and inner disk flows. These inner environments evolve on timescales of hours to days, exactly when bursts, dips, and rapid structural changes carry the most valuable information about star and planet formations, but remain hardly reachable with current facilities. A better reactive infrastructure with six or more telescopes, combined with alerts from large time-domain surveys (e.g., at the era of LSST/Rubin type facilities), and equipped with instruments spanning from the V-band to the thermal infrared (N), would provide the instantaneous uv-coverage and spectral diagnostics needed to unambiguously interpret and image these events as they happen. Such a world's first time-domain interferometric observatory would enable qualitatively new science: directly linking optical and infrared variability to spatially resolved changes in magnetospheric accretion, inner-disk geometry, and dust and gas dynamics in the innermost astronomical unit. Crucially, connecting these processes to outer-scale unresolved information from JWST, ALMA, and the ELT would yield a complete tomography of the planet-forming region.

In this paper, we extend a paper by Milgrom (2009, MNRAS 398, 1023) dealing with the existence of a quasi-universal surface density for object of all mass and structure, if they are in the Newtonian regime, i.e., that their mean acceleration is larger than MOND typical acceleration $a_0$. This result is in agreement with Donato et al. (2009)'s results, claiming the existence of a quasi-universal surface density in all masses in galaxies. The Milgrom paper also predicts that objects with mean inner acceleration smaller than the values discussed do %es not show the quasi-universal behavior of the surface density discussed. In the present paper, we extend the result of Milgrom's paper, based on a point mass model, considering spiral galaxies, modelled with a double exponential disk. Similar to Milgrom's results, we find the existence of a universal surface density for galaxies with large surface density, and a different behavior for galaxies having small surface density.

Young transiting exoplanets provide unique opportunities to probe planetary atmospheres during the critical early phases of evolution. HIP~67522~b, a 17~Myr old hot Jupiter with an extraordinarily low bulk density, represents an ideal target for high-resolution transmission spectroscopy. We aim to characterize the atmospheric composition, thermal structure, and dynamics of HIP~67522~b using ground-based high-resolution near-infrared spectroscopy. We obtained high-resolution spectra with VLT/CRIRES+ in the K2166 band during a transit on 30 January 2025. We applied cross-correlation techniques and Bayesian nested sampling retrievals to constrain molecular abundances, temperature structure, and atmospheric dynamics. We detect H$_2$O at 20$\sigma$ and CO at 5$\sigma$, confirming the extremely extended atmosphere of this low-mass giant. A velocity offset of $-2.9 \pm 0.2$~km~s$^{-1}$ indicates day-to-night winds. The rotation velocity is constrained to $<1.8$~km~s$^{-1}$ at 3$\sigma$, consistent with tidal locking. Retrieval analysis suggests a planetary mass of 29.8 $\pm$ 3 Earth masses and a vertically isothermal atmosphere. This mass is two times larger than the mass estimated from JWST atmospheric observations and inconsistent at 3$\sigma$ hence leaving a doubt on the actual planetary density of the planet. Using the mass derived derived from the CRIRES+ data, we derive a C/O ratio of $0.83 \pm 0.09$, about 1.5 times solar, and a subsolar metallicity [C+O/H]~$= -0.8 \pm 0.4$ which can be increased if the atmosphere is cloudy, a degeneracy our data alone cannot resolve. We report a tentative 2$\sigma$ detection of HDO with an extreme enrichment factor of $\sim$1000 relative to the protosolar D/H ratio. If confirmed, this would be the first detection of deuterium in an exoplanet atmosphere and would require intense escape rate to be explained.

Quasi-periodic pulsations (QPPs) are oscillatory signatures commonly detected in the light curves of solar and stellar flares, offering valuable diagnostics of the underlying magnetic and plasma processes. This review compares the observational characteristics, detection methods, and physical interpretations of QPPs in both solar and stellar contexts. Solar flare QPPs, extensively studied in X-rays and EUV bands using instruments such as GOES, STIX, and Fermi, display typical periods of tens of seconds and show correlations with flare duration and magnetic loop length. Stellar QPPs, observed in X-rays and white light by missions such as Kepler, TESS, and XMM-Newton, exhibit much longer periods - ranging from minutes to hours - consistent with larger-scale magnetic structures in more active stars. Despite differences in scale and observing band, statistical and comparative studies reveal common scaling relations and damping behaviors, suggesting that both solar and stellar QPPs are manifestations of the same fundamental mechanisms, likely magnetohydrodynamic oscillations or oscillatory reconnection within flare loops. The comparison underscores a continuity between solar and stellar magnetic activity, linking the solar detailed physical processes to stellar-scale phenomena and providing constraints for future models and surveys.

We present the results of three-dimensional magnetohydrodynamic (3D MHD) simulations of the plasma flow structure in the vicinity of a compact cluster of young massive stars. The cluster is considered at the evolutionary stage dominated by Wolf-Rayet stars. This stage occurs in clusters with ages of several million years, close to the onset of supernova explosions; the well-known objects Westerlund 1 and 2 are the prototypes. The collisions of powerful winds from massive stars in the cluster core, calculated as interactions of individual outflows, are accompanied by their partial thermalization and produce a collective cluster wind. The MHD dynamics of the cluster wind bubble expansion into the interstellar medium is considered, depending on the density of the surrounding medium with a uniform magnetic field. We show that when expanding into a cold neutral medium, the cluster wind is able to reshape its surrounding environment over the Wolf-Rayet star lifetime, sweeping up more than $10^4$ $M_{\odot}$ of gas in $\sim 2 \times 10^5$ yr and producing extended, thin and dense shells with an amplified magnetic field. In a cold neutral medium with a density of $\sim 20$ cm$^{-3}$ and a magnetic field of $\sim 3.5$ $\mu$G, a thin shell forms around the cluster wind bubble, characterized by a cellular structure in its density and magnetic field distributions. The cellular magnetic field structure appears in parts of the shell expanding transversely to the orientation of the external magnetic field. Magnetic fields in the shell are amplified to strengths $\gtrsim 50$ $\mu$G. The formation of the cellular structure is associated with the development of instabilities. The expansion of the bubble into a warm neutral interstellar medium also leads to the formation of a shell with an amplified magnetic field.

Recent theoretical and observational analysis of the interaction between the Milky Way (MW) and LMC suggest that it has a significant dynamical impact on the MW's stellar halo. We investigate this effect using simulations from the Latte project, a simulation suite from the Feedback In Realistic Environments 2 (FIRE-2) Project. By comparing simulations with and without an LMC-analog interaction, we show that fully cosmological LMC interactions create prominent velocity asymmetry in the stellar halo of the MW, resulting from both barycentric displacement (the "reflex motion") and the dynamical wake of the LMC. The strength and direction of this asymmetry depend on the mass ratio at pericenter and orbit of the LMC analog. We perform a spherical-harmonic decomposition of the velocities of halo star particles to confirm that the identified signatures are LMC-induced and persist even when LMC star particles are removed. We also show that this strategy separates and individually detects the dipole (l=1) of the global reflex motion and the quadrupole (l=2) of the local wake. These asymmetries are consistent with those identified in previous work using non-cosmological simulations; the dipole is easily distinguishable from other complex halo substructure using spherical harmonics while the quadrupole is sometimes confused. These findings support the detectability of MW--LMC interaction signatures in upcoming observational surveys of the MW stellar halo.

The present work aims at analyzing the nature of millimeter (mm) emission observed during the post-impulsive phase of the solar flare SOL2022-05-04T08:45 (M5.7), detected by the RT-7.5 radio telescope of the Bauman Moscow State Technical University at 93 GHz. We investigate the relationship of mm and extreme ultraviolet (EUV) emission with variations in the temperature and coronal plasma emission measure obtained from SDO/AIA and GOES data. The results show that the enhanced mm emission at the post-impulsive phase of the flare coincides with the increase of EUV emission, indicating a connection with moderately hot (~1 MK) plasma. Based on the calculation of the differential emission measure, we determine the parameters of the post-impulsive flare plasma and conclude that the optically thin coronal plasma may contribute of about 20% to the mm emission.

Narrow interstellar absorption features in supernova (SN) spectra serve as valuable diagnostics for probing dust extinction and the presence of circumstellar or interstellar material. In this third paper in a series, we investigate how the strength of narrow interstellar absorption lines in low-resolution spectra varies with SN type and host galaxy properties, both on local and global scales. Using a dataset of over 10000 spectra from $\sim1800$ low-redshift SNe, we find that Type Ia SNe (SNe Ia) in passive galaxies exhibit significantly weaker narrow absorption features compared to CC-SNe and SNe Ia in star-forming hosts (SNe Ia-SF), suggesting lower interstellar gas content in quiescent environments. Within the star-forming hosts, the Na I D equivalent-width distribution of SNe II is much lower than that of both SNe Ia-SF and stripped-envelope SNe (SE-SNe). This result is somewhat unexpected, since CC-SNe are generally associated with star-forming regions and occur deeper within galactic disks, where stronger line-of-sight extinction would be anticipated. This suggests that the observed behaviour cannot be explained solely by absorption from the integrated interstellar medium (ISM) along the line of sight. Instead, if part of the absorption arises from material near the explosion, the similarity between the Na I D EW distributions of SNe Ia-SF and SE-SNe implies that comparable absorption signatures can emerge from distinct progenitor pathways. Possible explanations include (a) circumstellar material (CSM) expelled by the progenitor system before explosion, or (b) interaction of SN radiation with nearby patchy ISM clouds. Our results highlight the diagnostic power of interstellar absorption features in revealing the diverse environments and progenitor pathways of SNe.

Context: The role of Pluto contributing to the long-term evolution of the trans-Neptunian region has been considered significant only over its neighboring Plutinos. However, it has recently been found that the long-term stability of the Twotino population is strongly affected when including Pluto as a massive object in simulations, while Eris, with a similar mass, has a negligible effect. Aims: We hypothesize that the effect of Pluto on Twotinos results from the latter being trapped in a 4:3 mean motion resonance (MMR) with Pluto. In this work, we aim to demonstrate the resonant behavior of Twotinos within Pluto's 4:3 MMR and the significance of this resonance for the long-term evolution of the population. Methods: We run high-resolution, 10 Myr REBOUND simulations of the observed Twotino population in the Kuiper belt, under the perturbations of the Sun, the four giant planets, and Pluto, as massive objects. Results: We find that all objects trapped in the 2:1 MMR with Neptune are locked in a weak 4:3 MMR with Pluto. The 4:3 resonant angles of most objects trapped in the leading and trailing islands of the 2:1 MMR, librate with amplitudes lower than $360^\circ$. Objects in the symmetric islands of the 2:1 MMR librate in the 4:3 MMR with amplitudes greater than $360^\circ$, but, contrary to circulating objects, will oscillate by up to $840^\circ$ visiting preferred angles on Pluto's co-rotating frame, indicating a diluted resonant effect that may also perturb their orbits on secular timescales. Conclusions: The importance of Pluto in shaping the structure of the trans-Neptunian region should be reconsidered, especially for resonant populations. Moreover, with current computational power, its exclusion from simulations can not be justified.

Thermal radiation transport is a challenging problem in computational physics that has long been approached primarily in one of a few standard ways: approximate moment methods (for instance P$_1$ or M$_1$), implicit Monte Carlo, discrete ordinates, and long characteristics. In this work we consider the efficacy of the Method of (Long) Characteristics (MOC) applied to thermal radiation transport. Along the way we develop three major ideas: transporting MOC particles backwards in time from quadrature grids at the end of the timestep, limiting the computational cost of these backward characteristics by terminating transport once optical depths along rays become sufficiently large, and timestep-dependent closures with multigroup MOC solutions for a gray low-order system. We apply this method to a suite of standard radiation transport and radiation hydrodynamics test problems. We compare the method to several standard analytic and semi-analytic solutions, as well as implicit Monte Carlo, P$_1$, and discrete ordinates (S$_n$). We see that the method: gives excellent agreement with known results, has stability for large time steps, has the diffusion limit for large spatial cells, and achieves $\sim$20-70\% performance improvement when terminating optical depths at O(10-100) in the grey Marshak and crooked pipe problems. However, for the Coax radiation-hydrodynamics problem, we see that MOC is approximately two to three times slower than IMC-DDMC and S$_n$ in its current implementation.

In isolated binary evolution, binary black hole (BBH) mergers are generally formed through stable mass transfer (SMT) or common envelope evolution. In recent years, the SMT channel has received significant attention due to detailed binary models showing increased mass transfer stability compared to previous studies. In this work, we perform a full zero-age-main-sequence to compact object merger analysis using detailed binary models at eight metallicities between $10^{-4}Z_\odot$ and $2Z_\odot$ to self-consistently model the population properties of BBH mergers in the SMT channel, determined their progenitor initial conditional, and investigate the binary physics governing their formation and metallicity dependence. We use the population synthesis code POSYDON to determine the population of BBH mergers from SMT. Using its extended grids of MESA binary models, we determine the essential physics in the formation of BBH mergers. SMT produces BBH mergers predominantly from systems with $P_{ZAMS}\leq10$ days. In these systems, both the initial mass transfer between two stars and the subsequent interaction between the remaining star and the first-born BH take place while the respective donor star is on the main-sequence (Case A). We find a limited contribution from wider Case B/C systems. Without a natal kick, the SMT channel does not produce BBH mergers above $Z>0.2Z_\odot$ due to orbital widening from stellar wind mass loss. The primary BH mass distribution shows a strong dependence on metallicity, while the mass ratio prefers unity independent of metallicity due to mass ratio reversal. Additionally, the $\chi_{eff}$ distributions contain peaks at $\chi_{eff}=0$ and ~0.15 of which the former disappears at high metallicities. A mass-scaled natal kick leave this sub-population unchanged but introduce a low-mass, unequal mass ratio sub-population that merges due to their high eccentricity.

Type II supernovae (SNe II) are the most common terminal stellar explosions in the Universe. With SNe now being detected within days after explosion, there is growing evidence that the majority of Type II SNe show signs of interaction with a confined, dense cirumstellar material (CSM) in the first few days post explosion. In this work we aim to bridge the gap between single SN studies showing early-time interaction in their spectra, and the statistical studies of early-time SN light curves, which imply the existence of CSM. We present a sample of 68 Type II SNe with both early photometric data, obtained with the ATLAS survey, and spectroscopic data, obtained with the ePESSTO+ collaboration. A subset of the sample is classified based on the presence or absence of narrow spectral features with electron-scattered broadened wings in the early spectra, indicative of interaction with CSM. We characterise the photometric and spectroscopic properties of the sample by measuring rise times to maximum light, peak magnitudes, decline rates and line velocities. Additionally, we measure the ratio of absorption to emission (a/e) of the H alpha P-Cygni profile. Our analysis reveals that SNe II showing early spectroscopic signs of interaction with CSM decline faster and are brighter than those without. However no difference is found in rise times between the two groups. A clear separation is observed in the a/e ratio: SNe with signs of interaction exhibit lower a/e ratios at all epochs compared to those without. Our results highlight that understanding SN II ejecta-CSM interaction requires large, uniform samples of photometric and spectroscopic data, such as the one presented in this work.

Massive O-type stars ($M\gtrsim15\,M_\odot$) with an X-ray quiet black hole (BH) companion represent a crucial stage in massive binary evolution leading to binary BH mergers. The population of such binaries remains elusive, with $\lesssim5$ candidate or confirmed systems. The Tarantula nebula harbors thousands of massive stars, 2-3 % of which are expected to have BH companions. It is therefore an ideal place to hunt for such systems. Here we analyse 30 epochs of VLT/FLAMES IFU high-resolution observations of the H$\delta$ region, as well as archival FLAMES spectroscopy, of VFTS 812, a 17-day single-lined spectroscopic binary with an O4V primary and a minimum secondary mass of $5.1\,M_\odot$. Following careful removal of the nebular contamination, spectral disentangling on the new data did not reveal any signature of the hidden companion. We derive $T_\mathrm{eff}=49^{+3}_{-4}$ kK, $\log L/L_\odot=5.7\pm0.1$ and $v_\mathrm{rot,max}{\rm \,sin\,}i=110^{+25}_{-35}$ km/s for the O4V component, yielding a (single star) evolutionary mass of $53^{+6}_{-5}$ $M_\odot$ and an age in the range of 0-1.6 Myr. Using injection tests of various luminous artificial companions in our data, we exhaustively rule out the presence of any luminous signature from a main sequence star more massive than $6\,M_\odot$. We discuss the possible nature of the companion, suggesting that the rejuvenated O star + BH companion is the most suitable scenario to consistently explain the location, (rejuvenated) young age, eccentricity and lack of companion signature. While this establishes VFTS 812 as a strong candidate O+BH system, follow-up observations are deemed necessary for robust confirmation and to search for accretion signatures on the O4V star.

Deuterium fractionation is highly efficient during the early stages of star formation, particularly in starless and prestellar cores where temperatures are low (<10 K) and molecular freeze-out onto dust grains is significant. Methanol forms early in these environments following CO freeze-out via successive hydrogenation reactions on grain surfaces, while the production of deuterated methanol requires elevated gas-phase D/H ratios generated through dissociative recombination of deuterated H3+. Consequently, large abundances of deuterated methanol are observed toward young stellar objects where prestellar ices have recently sublimated. Here, we present laboratory infrared spectra of methanol and its deuterated isotopologues in astrophysical ice analogues, complemented by anharmonic vibrational calculations used to guide band assignments. Experiments were performed at the CASICE laboratory using a Bruker Vertex 70v spectrometer coupled to a closed-cycle helium cryostat, with isotopologue ices deposited at 10 K under high-vacuum conditions. Infrared transmission spectra were recorded over 6000-30 cm-1 (1.67-333 um) and compared with spectra of pure isotopologue ices. Distinctive mid-infrared band patterns are identified for each deuterated species. In particular, CH2DOH exhibits a characteristic doublet at 1293 and 1326 cm-1 (7.73 and 7.54 um), while CHD2OH shows a similar doublet at 1301 and 1329 cm-1 (7.69 and 7.52 um), both remaining largely invariant across all studied ice mixtures. These robust spectral signatures provide reliable tracers for identifying deuterated methanol in JWST observations and for constraining astrochemical gas-grain models of deuterium enrichment prior to star and planet formation.

The current census of planetary systems displays a wide range of architectures. Extending earlier work, this paper investigates the correlation between our classification framework for these architectures and host stellar properties. Specifically, we explore how planetary system properties depend on stellar mass and stellar metallicity. This work confirms previously detected trends that jovian planets are less prevalent for low-mass and low-metallicity stars. We also find new, but expected trends such as that the total mass in planets increases with stellar mass, and that observed planetary system masses show an upper limit that is roughly consistent with expectations from the stability of circumstellar disks. We tentatively identify potential unique trends in the host stars of super-puffs and hot jupiters and a possible subdivision of the class of hot jupiter systems. In general, we find that system architectures are not overly dependent on host star properties.

The most productive tracer of exoplanetary atmospheric escape is the measurement of excess absorption in the near-infrared metastable helium triplet during transits. Atmospheric escape of a close-in planet's atmosphere plays a role in its evolutionary pathway, but to which extent remains unknown. It could explain demographic features like the radius valley and Neptunian desert. We will describe the development of instrumental, reduction, and modelling techniques to study exoplanetary atmospheric escape, focusing on the helium triplet. One such development is the NIGHT spectrograph, intended to provide the first survey of escaping atmospheres. NIGHT spectra will be processed with ANTARESS, a state-of-the-art workflow for reducing high-resolution spectral time-series of exoplanet transits and computing transmission spectra in a robust and reproducible way. Transmission spectra contain the potential signature of the planetary atmosphere as well as distortions induced by the occultation of local regions of the stellar surface along the transit chord. Transmission spectra cannot be corrected for those stellar distortions without biasing the planetary signal. They must instead be directly interpreted using a numerical model like the EvE code, which generates realistic stellar spectra that account for the system's 3D architecture, the planet's atmospheric structure, and its local occultation of the stellar disc. This global approach, from the measurement and computation of transmission spectra to their interpretation, will be a legacy of the NCCR PlanetS, becoming the standard procedure to study high-resolution spectroscopy of planetary transits.

Interstellar medium studies rely on magnetohydrodynamic (MHD) turbulence as a framework for interpretation. In this context, the statistical characterization of interstellar observations is of prime importance. We open a new perspective on diffuse interstellar matter by analyzing James Webb Space Telescope (JWST) observations of the Pleiades nebula with NIRCam. These observations are remarkable in that they provide a microscope view at the cold neutral medium (CNM) with a spatial resolution of 0.2 mpc (40 au). A two-dimensional Fourier analysis is used to characterize the structure of PAH emission in regions near and far from the Pleiades star Merope. To produce maps of the interstellar emission, stars and galaxies are filtered out. The final step in the data cleaning involves subtracting a component, in Fourier space, which we infer to be a residual of the near-infrared cosmic background. The PAH emission power spectra are highly anisotropic. They are well fitted with a break-free power-law, suggesting that we do not observe a specific scale for energy dissipation. Power-law indices are -3.5 near Merope and -3 in the more distant field. The magnetic field orientation, as derived from the Planck dust polarization data, aligns with the PAH anisotropy. The power anisotropy is constant across scales. These findings are discussed in relation to interstellar turbulence that may be driven by the Pleiades stars. The JWST observations of the Pleiades offer a new viewpoint for comparing observations and theoretical models, as they examine physical scales at which turbulence in the CNM is subsonic and decoupled from the thermal instability. The observations may indicate that the turbulent energy cascade in the CNM is anisotropic.

Numerical simulations are a key tool to decipher the dynamics of gravitation. Yet, they fail to spatially reproduce the Universe we observe, limiting comparison between observations and simulations to a statistical level. This is highly problematic for rare, faint or well studied nearby objects that are observed in a single environment. The computational cost of recovering this environment in random simulations is prohibitive. We present Hamlet-PM, a method that enables the constraining of initial conditions for cosmological simulations so as to produce evolved numerical universes that can be directly compared to observations of the Local Universe: constrained simulations. Our method implements the field-level forward modeling of the early-time density field from sparse and noisy measurements of late-time peculiar velocities. The dynamics are integrated with a particle-mesh gravity solver, thus probing the mildly non-linear regime. The code is applied to the Cosmicflows-4 compilation of peculiar velocities up to z < 0.05 (160 Mpc/h). The constrained ICs a re-simulated with a high precision N-body code. A series of one hundred dark-matter only cosmological constrained simulations with a resolution of 512^3 particles in a 500^3 [Mpc/h]3 box is presented. Special attention is given to twelve prominent nearby galaxy clusters, whose simulated counterparts are matched on criteria of mass and separation. We provide a mass estimate constrained by the dynamical environment for each cluster. Field-level forward modeling of the initial conditions produces highly constrained cosmological simulations. Currently, this method already overtakes in quality the pipeline in use in the peculiar-velocity community, although systematic biases still need to be addressed. Furthermore, improving the model is easy thanks to the inherent flexibility of the Bayesian approach.

Tidal interactions play a crucial role in the orbital evolution of close-in star-planet systems. There are numerous manifestations of tides, including planetary orbital migration, breaking resonant chains, tidal heating, orbital circularization, spin-orbit alignment, and stellar and planetary spin synchronization. In the present study, we focus on the dissipation of internal gravity waves within stars. We examine two mechanisms: wave breaking in stars with radiative cores and magnetic wave conversion in stars with convective cores. Applying tidal prescriptions modelling these processes, we demonstrate that the enhanced stellar rotation of both TOI-2458 and GJ 504 can be explained by the previous engulfment of a hot Jupiter caused by gravity wave damping. Furthermore, we show that the observed population of hot Jupiters can be divided into two distinct subsamples: those that are too young for gravity wave dissipation and those where it is ongoing. These subsamples exhibit qualitatively different orbital period distributions: young systems have a uniform distribution, while older systems show a steep decline at short orbital periods. Using a population synthesis approach, we successfully reproduce the main features of the older hot Jupiter sample based on the distribution of the younger systems. According to our estimates, up to 20% of the main-sequence stars within the mass range [0.7,1.5] $M_{\odot}$ that once hosted a hot Jupiter may have since engulfed it. Our results highlight the key role of internal gravity wave dissipation in shaping the orbital architectures of hot Jupiter systems.

We study the temporal evolution of solar inertial modes over the solar cycle using observations from GONG and SDO/HMI. We focus on the high-latitude mode with azimuthal wavenumber $m=1$ and the equatorial Rossby modes with $3 \le m \le 16$. We use maps of horizontal flows near the solar surface from the GONG and HMI ring-diagram pipelines at a cadence of approximately one day, covering the period 2002--2024. The data are divided into overlapping four-year windows, with central times separated by six months. Within each time window and for each inertial mode, we measure the frequency and the power of the mode from the GONG and HMI data. We find good agreement between the GONG and HMI measurements throughout their overlapping period from 2010 to 2024. In general, the magnitude of the frequency variations increases with increasing $m$, while relative changes in mode power typically exceed 100\%. For the $m=1$ high-latitude mode, the measured power is anti-correlated with the sunspot number, while its frequency shows no significant temporal variation. For the equatorial Rossby modes, the frequencies are generally anti-correlated with the sunspot number, whereas the mode powers tend to correlate positively with the sunspot number. An exception is the $m=3$ equatorial Rossby mode, whose mode power is strongly anti-correlated with the sunspot number, in contrast to the other equatorial Rossby modes, highlighting its distinct behavior. We find that the frequencies and power of the Sun's inertial modes exhibit significant variability on solar-cycle timescales over the past 23 years. The mode parameters are however not uniformly synchronized with the sunspot number; clear differences are observed both from mode to mode and from one solar cycle to the next. The sensitivity of inertial modes to solar-cycle changes indicates their potential as a diagnostic of solar interior dynamics and magnetism.

Two-photon polymerization (2PP) enables fabrication of high-precision micro-optics with complex freeform geometries, opening a new parameter space for custom astronomical optics. Among available resins, the newly developed IPX Clear is particularly well suited for visible applications, offering high transmission across the visible-near-IR, low surface roughness, and excellent shape fidelity. However, Fresnel reflections at the air-polymer interface introduce significant optical losses, which are detrimental in low-signal astronomy. Previous studies show grass-like alumina coatings on glass and fused silica can raise average transmission from 91.9% to approximately 99% over 400-900 nm. Here we explore the feasibility of Atomic Layer Deposition (ALD) to apply such coatings to IPX-Clear micro-optics over 400-1700 nm. Grass-like alumina anti-reflective (AR) coatings can approximate the ideal index condition by creating a gradual refractive-index transition from air to bulk IPX Clear, suppressing surface reflections. While grass-like coatings are established on bulk optics and conformal ALD films have been applied to 2PP micro-optics, we demonstrate - for the first time - alumina grass on 2PP microlenses made with the new IPX-Clear resin. We discuss key challenges and process steps, and observe that alumina-grass-coated microlenses lose only approximately 0.3% of photons to reflection in the 400-850 nm range. Future work will test performance across the full 400-1700 nm band and explore improved environmental resilience, e.g., a SiO2 overcoat. Combined with the high optical transparency of IPX Clear, these coatings enable custom-designed, highly efficient microlenses for astronomical applications.

Lunar regolith, the layer of unconsolidated material covering the Moon's surface, is central to the science and technology developed for the Moon, notably related to in-situ science investigations, resource utilization, surface infrastructure, and mobility systems. However, data on lunar soil properties remain fragmented across decades of mission reports, often in formats that are difficult to access or interpret. We present a newly compiled database of lunar regolith physical and geotechnical properties, including data collected by direct in-situ measurements from crewed missions, estimates inferred from surface interactions on the Moon and using remote sensing, as well as laboratory analyses of samples returned to Earth. The data collected include, among others, the angle of internal friction and cohesion (both Mohr-Coulomb model parameters), bulk density, and static bearing capacity, extracted from Luna and Apollo-era historical mission documentation all the way to contemporary Lunar programs. The dataset specifies the type and location of the tests from which each value was obtained. Our database also includes parameters for lunar regolith simulants, providing a direct link between mission data and laboratory studies. In addition to centralizing this information, we developed a user interface that facilitates data retrieval, filtering, and visualization. This interface enables users to generate customized plots for comparative analysis. Developed in an open-science perspective, it is designed to evolve in response to the community's needs. The database and its associated tools significantly enhance the accessibility and usability of lunar regolith and simulants data for scientific and engineering research.

Ultra-fast outflows (UFOs) are thought to be a driving mechanism of large-scale winds driven by active galactic nuclei, which cause significant galactic feedback through quenching star formation and regulating supermassive black hole growth. We present James Webb Space Telescope (JWST) Mid-Infrared Instrument Medium-Resolution Spectrometer observations of two nearby ultraluminous infrared galaxies (ULIRGs), F11119+3257 and F05189-2524, with nuclear X-ray detected UFOs and kiloparsec-scale outflow. These galaxies show remarkably similar mid-infrared continuum and emission line features, notably including a high-velocity $v_{90}$ $\sim$ 4000 km s$^{-1}$ outflow detected in highly ionized neon emission lines, e.g., \nevi. In F05189-2524, we see a slightly slower biconical outflow extending up to $\sim2$ kpc in the same neon emission lines. Both sources show evidence of AGN-driven radiative feedback through a deficit of rotational molecular hydrogen lines in the nuclear region, $<$1 kpc from the central quasar, but no clear evidence of any molecular gas entrained in the quasar-driven outflow. Energetic analysis shows that the warm ionized gas in both of these sources contributes minimally ($\sim0.1-5\%$) to the momentum outflow rate of these sources and leaves the conclusions of previous literature unchanged: the energetics of these sources are broadly consistent with a momentum-conserving outflow.

We investigate whether late-time modifications of gravity in the teleparallel framework can impact the current tension in the Hubble constant $H_0$, focusing on $f(T)$ cosmology as a minimal and well-controlled extension of General Relativity. We consider three representative $f(T)$ parametrisations that recover the teleparallel equivalent of General Relativity at early times and deviate from it only at late epochs. The models are confronted with unanchored Pantheon+ Type~Ia supernovae, DESI DR2 baryon acoustic oscillations, compressed Planck cosmic microwave background distance priors, and redshift-space distortion data, allowing us to jointly probe the background expansion and the growth of cosmic structures. Two of the three models partially shift the inferred value of $H_0$ towards local measurements, while the third worsens the discrepancy. This behaviour is directly linked to the effective torsional dynamics, with phantom-like regimes favouring higher $H_0$ and quintessence-like regimes producing the opposite effect. A global statistical comparison shows that the minimal $f(T)$ extensions considered here are not favoured over $\Lambda$CDM by the combined data. Nevertheless, our results demonstrate that late-time torsional modifications can non-trivially redistribute current cosmological tensions among the background and growth sectors.

We investigate a bouncing cosmological model within the Weyl-type $f(Q)$ gravity framework, employing a power-law form of the non-metricity scalar $Q$. The model successfully resolves the initial singularity problem by demonstrating a nonsingular bounce, where the universe transitions from a contracting phase $ \dot{a}(t)<0 $ to an expanding phase ($ \dot{a}(t)>0 $) at the bouncing point $t \approx 0.$ Key features include the violation of the null energy condition (NEC) near the bounce and the crossing of the phantom divide line ($\omega=-1$) by the equation of state (EoS) parameter, indicating quintom-like behavior. The model exhibits accelerated expansion post-bounce, suggesting an inflationary phase. Stability analysis via the adiabatic index reveals instability near the bouncing point, while energy conditions highlight the dominance of dark energy. Additionally, the study explores scalar fields, showing that quintessence-like kinetic energy becomes negative and phantom-like kinetic energy peaks positively near the bounce, aligning with dark energy dynamics. The Hubble parameter, deceleration parameter, and Hubble radius further validate the bouncing scenario, with the latter displaying symmetric behaviour around the bounce. These results underscore the viability of Weyl-type $f(Q)$ gravity as a framework for nonsingular bouncing cosmologies, offering insights into early universe dynamics and dark energy behaviour.

We construct a charged Bardeen black hole (BH) surrounded by perfect fluid dark matter (PFDM) and coupled to a cloud of strings (CS). The metric function combines the magnetic monopole charge from nonlinear electrodynamics, the PFDM logarithmic correction, and the CS parameter that renders the spacetime asymptotically non-flat. We analyze the horizon structure, identifying parameter ranges yielding non-extremal BHs, extremal configurations, and naked singularities. The null geodesics, photon sphere radius, and shadow are computed, revealing that both CS and PFDM enlarge the shadow. For neutral particle dynamics, we derive the specific energy, angular momentum, and innermost stable circular orbit location. Quasiperiodic oscillations (QPOs) are examined through the azimuthal, radial, and vertical epicyclic frequencies, where notably the azimuthal frequency is independent of the CS parameter. Scalar field perturbations governed by the Klein-Gordon equation yield an effective potential whose peak decreases with both parameters, yet the transmission and reflection probabilities respond oppositely to CS and PFDM variations. The greybody factor bounds are obtained using semi-analytical methods. Our results demonstrate that the distinct effects of $\alpha$ and $\beta$ on various observables could allow independent constraints on these parameters through shadow measurements, QPO timing, and gravitational wave ringdown observations.

We construct a charged Bardeen black hole (BH) surrounded by perfect fluid dark matter (PFDM) and coupled to a cloud of strings (CS). The metric function combines the magnetic monopole charge from nonlinear electrodynamics, the PFDM logarithmic correction, and the CS parameter that renders the spacetime asymptotically non-flat. We analyze the horizon structure, identifying parameter ranges yielding non-extremal BHs, extremal configurations, and naked singularities. The null geodesics, photon sphere radius, and shadow are computed, revealing that both CS and PFDM enlarge the shadow. For neutral particle dynamics, we derive the specific energy, angular momentum, and innermost stable circular orbit location. Quasiperiodic oscillations (QPOs) are examined through the azimuthal, radial, and vertical epicyclic frequencies, where notably the azimuthal frequency is independent of the CS parameter. Scalar field perturbations governed by the Klein-Gordon equation yield an effective potential whose peak decreases with both parameters, yet the transmission and reflection probabilities respond oppositely to CS and PFDM variations. The greybody factor bounds are obtained using semi-analytical methods. Our results demonstrate that the distinct effects of $\alpha$ and $\beta$ on various observables could allow independent constraints on these parameters through shadow measurements, QPO timing, and gravitational wave ringdown observations.

This letter proposes a new avenue for understanding the cosmological singularity. The standard cosmological model contains a generic initial singularity usually referred to as the {\em big bang}. Herein, we present a novel idea to extend the description of our Universe beyond this limit. The proposal relies on rewriting physics in a purely Riemannian, {\em i.e.} locally Euclidean, 4-dimensional space and the emergence of Lorentzian patches owing to the interaction of all matter fields to a clock field that is responsible for a signature change. If our universe is contained within one of these patches, the initial singularity is replaced by a smooth boundary on which the signature of the physical metric flips. In this letter, we first define the model and draw the necessary conditions on its arbitrary functions for solutions to exist. Next, we prove the existence of solutions that lead to an emergent universe with a primordial (almost) de Sitter phase. To finish, we discuss the consequences of this construction for the universe on scales much larger than our observable universe: a large ``Euclidean sea'' in which Lorentzian islands locally emerge and host an expanding universe potentially similar to ours. While speculative, this scenario has specific features that can be tested, and the present letter sets the basis for further phenomenological investigations.

If a strong first-order phase transition takes place at sufficiently high rest-mass densities in the equation of state (EOS) modelling compact stars, a new branch will appear in the mass-radius sequence of stable equilibria. This branch will be populated by stars comprising a quark-matter core and a hadronic-matter envelope, i.e., hybrid stars, which represent ``twin-star'' solutions to equilibria having the same mass but a fully hadronic EOS. While both branches are stable to linear perturbations, it is unclear which of the twin solutions is the ``favoured'' one, that is, which of the two configurations is expected to be found in nature. We assess this point by performing a large campaign of general-relativistic simulations aimed at assessing the response of compact stars on the two branches to perturbations of various strength. In this way, we find that, independently of whether the stars populate the hadronic or the twin branch, their response is characterised by a critical-perturbation strength such that the star will oscillate on the original branch for subcritical perturbations and migrate to the neighbouring branch for supercritical perturbations while conserving rest-mass. Because the critical values are different for stars with the same rest-mass but sitting on either branch, it is possible to define as favoured the part of the branch that has the largest critical perturbation, thus correcting the common wisdom that stellar models on the twin branch are the favoured ones. Interestingly, we show that the binding energies on the two branches can be used to deduce without simulations which of the stellar configurations is more likely to be found in nature.

A system of classical interacting spins can develop collective instabilities which, in the nonlinear regime, mimic the motion of a gyroscopic pendulum. Known as the flavor pendulum, this behavior appears among the collective modes of a dense neutrino plasma after a strong reduction of phase space through symmetry assumptions. It has been identified in homogeneous slow and fast flavor systems and, most recently, in single-wave solutions of the fast system. We explain the reasons for its ubiquitous appearance. We show that a system of three classical spins must always be pendular, or only two in the presence of an external field. Furthermore, such a system always defines a continuum of vectors with time-independent length. If these are identified as interacting spins, they immediately lead to the continuum cases of slow and fast flavor pendula. As another new insight, any of these spins can be chosen as the pendulum, periodically exchanging flavor with the rest of the system.

We revisit the Hartle-Hawking no-boundary proposal. To extract probabilities, one must use the gravitational path integral (GPI) to compute not only the no-boundary amplitude, but also the norms by which its square is divided. We find that this dramatically alters predictions: the probability for any closed universe is either nearly 1, or exactly 1. That is, in the Hilbert space of closed universes defined by the GPI, the states of interest in cosmology are all nearly parallel to the Hartle-Hawking state up to nonperturbative corrections in $G_N^{-1}$. We also consider a statistical interpretation of the GPI, as an average of arbitrary products of amplitudes. We find that all amplitudes are exactly 1 in this case, consistent with recent arguments that the statistical approach to the GPI with a closed boundary computes an average over one-dimensional Hilbert spaces. As an example, we illustrate the consistent evaluation of the no-boundary proposal in inflationary cosmology.

Motivated by the recent evidence of a stochastic gravitational wave background found by pulsar timing array experiments, we focus on one of the prime cosmological explanations, i.e. a supercooled first order phase transition. If confirmed, it would offer a unique opportunity to probe early Universe dynamics and the related physics beyond the Standard Model of particles and interactions. However, the prediction of the gravitational wave spectrum from a given particle physics scenario requires theoretically and computationally demanding methods. While several tools have been put forward to reduce uncertainties and automatize these computations, we study here the possibility to perform the full pipeline of computations semi-analytically in the $4D$ theory, thus avoiding computationally intensive simulations. Our approach yields accurate results that can be used in phenomenological studies and allow for an efficient exploration of the connection between the particle physics models and their cosmological predictions.

Second-order structure functions and power spectral densities are popular tools in the study of statistical properties across scales, particularly for the analysis of turbulent flows. Although intimately related, analyses primarily use one or the other. We introduce a framework for estimating the power spectrum using the second-order structure function without applying Fourier transforms -- enabling one to take advantage of the real-space structure function calculations. We validate and showcase this method, comparing it to classical Fourier power spectrum estimates determined from analytical calculations, fractional Brownian motion, turbulence simulations, and space-physics and astrophysical observations of turbulence. We show that this method is able to robustly obtain the expected power law behaviour where we use turbulence ranges as test-cases.

A major source of uncertainty in modeling the strangeness-rich interiors of neutron stars arises from the poorly constrained two-body and three-body interactions among hyperons and nucleons. We perform a comprehensive Bayesian analysis of the $\Lambda\Lambda$ and $\Lambda\Lambda N$ interaction parameters within the Skyrme Hartree-Fock framework, constrained by both hypernuclei experimental data and astrophysical observations. Our results show that the parameter space of the $\Lambda\Lambda$ interaction is tightly constrained by combining nuclear and astrophysical data, while the parameters of the $\Lambda\Lambda N$ three-body interaction remain sensitive to astrophysical inputs alone. Specifically, the local, momentum-independent two-body interaction parameter $\lambda_0$ is tightly constrained and predominantly attractive, while the momentum-dependent parameters $\lambda_1$ and $\lambda_2$ contribute repulsive effects at high densities. A key role is played by the $\Lambda\Lambda$ potential depth in pure $\Lambda$ matter, which effectively constrains the two-body $\Lambda\Lambda$ interaction and governs the balance between attraction at low densities and repulsion at high densities. The repulsive components of $\Lambda\Lambda$ interactions then decrease hyperon fractions and reconcile hyperon-rich equations of state with the observed $\sim2\,M_{\odot}$ neutron stars, increasing the maximum mass by up to 22\%. The inclusion of $\Lambda\Lambda N$ three-body forces further stiffens the EOS, raising the maximum mass by up to $\sim 0.1\,M_{\odot}$. Our study represents a promising step toward a complete, experimentally grounded description of dense matter across a wide range of densities and strangeness compositions.

We analyze \emph{Parker Solar Probe} and \emph{Solar Orbiter} measurements of magnetic-field reversals (``switchbacks'') across the Alfvén surface ($M_a\simeq 1$), where $M_a$ is the Alfvén Mach number. The reported ``sub-Alfvénic switchback dropout'' follows from two diagnostic biases: conditioning on an instantaneous $M_a$, which is transiently elevated above unity by radial-velocity enhancements during large-amplitude Alfvénic rotations, and short-window local-mean backgrounds that partially track these rotations and suppress deflection angles. Treating $M_a$ as a bulk-stream property via rolling medians and referencing deflections to event-independent backgrounds -- a Parker-spiral direction or a sufficiently long rolling median -- recovers sub-Alfvénic switchbacks systematically. The mean deflection $\langle \theta \rangle$ separates into two regimes with $M_a$. For $M_a \lesssim 1$, $\langle \theta \rangle$ rises rapidly with weak dependence on the background window, consistent with expansion-driven amplification of Alfvénic fluctuations. For $M_a \gtrsim 1$, the evolution becomes scale dependent: large-scale $\langle \theta \rangle$ continues to grow with $M_a$ at reduced rate, while small-scale growth saturates, consistent with turbulent decay and dissipation. Collectively, these results indicate that switchbacks need not originate only in the super-Alfvénic solar wind. Instead, they are consistent with a formation pathway in which coronal fluctuations are amplified by large-scale expansion through the sub-Alfvénic regime, with subsequent propagation into the super-Alfvénic wind where turbulent decay modifies their scale-dependent properties.

Ultra-high-energy cosmic rays (UHECRs) can be detected via the broadband radio pulses produced by their extensive air showers. The Giant Radio Array for Neutrino Detection (GRAND) is a planned radio observatory that aims to deploy autonomous antenna arrays over areas of order $\sim 10^5\,\mathrm{km}^2$ to detect this emission. However, Galactic and instrumental radio backgrounds make the identification of low signal-to-noise ratio (SNR) pulses a central challenge. Here, we present a deep convolutional denoiser model that jointly processes each GRAND antenna trace in the time and frequency domains, allowing the network to learn transient pulse morphology and broadband spectral features while suppressing background noise. By training the model on $4.1\times 10^5$ simulated traces that include detailed UHECR radio emission and realistic detector response and noise, we find a median output-SNR improvement of $\sim 15-23\,\mathrm{dB}$ in the $50-200~\mathrm{MHz}$ band and a reduction of the normalized mean squared error of the waveform by about an order of magnitude relative to a Hilbert-envelope denoiser baseline. We also verify that applying the denoiser to noise-only windows does not produce spurious pulse candidates. Near the detection threshold, the denoiser increases the number of antennas contributing reliable pulse timing by a factor of $\sim 2-3$, which correspondingly tightens direction reconstruction uncertainties. When we additionally require accurate recovery of the waveform shape, the denoiser yields a median gain of $\sim 3-4$ antennas usable for energy reconstruction at SNR$\simeq 5-6$, strengthening event-level direction and energy estimates in sparse radio arrays.

Recent theoretical work has revealed that basic observables of quantum field theory in de Sitter space, known as in-in or cosmological correlators, exhibit surprisingly simple mathematical structure reminiscent of scattering amplitudes in flat space. For many theories, this simplicity can be made manifest using a set of ``cosmological dressing rules'' which uplift flat-space Feynman diagrams to in-in correlators in de Sitter space by attaching auxiliary propagators to the interaction vertices. In this paper, we show that discontinuities of cosmological correlators with respect to internal energy variables can be obtained by applying auxiliary propagators to unitarity cuts of flat space Feynman diagrams. Moreover, discontinuities with respect to external energy variables can be obtained by cutting auxiliary propagators attached to Feynman diagrams. This observation in turn implies highly non-trivial constraints on cosmological correlators in the form of simple sum rules. We illustrate these ideas in a number of examples at tree-level and 1-loop for conformally coupled scalar theories, although they hold more generally. Finally, we show how to reconstruct cosmological correlators from their discontinuities using dispersion relations, providing a powerful new approach to computing cosmological observables by systematically reconstructing them from data uplifted from flat space.