Papers for Wednesday, Apr 15 2026

We study the effect of temperature on secular, compositional $g$-modes in the core of inviscid neutron stars. Using a chiral $SU(2)_f$ sigma model, we construct isentropic temperature profiles for hot and dense matter and find that the frequency of the global core $g$-mode's dependence on temperature is governed by the nuclear symmetry energy slope parameter $L$. As a result, the $g$-mode frequency of a warm neutron star can be either higher or lower than that of its cold counterpart, depending on $L$. Our results highlight the interplay of thermal effects and composition gradients, and demonstrate the potential of neutron star $g$-mode observations to constrain the density dependence of the symmetry energy.

The advent of high-fidelity imaging of supermassive black holes calls for efficient and robust data-analysis methods. In this work, we use $\texttt{Jipole}$, a differentiable, $\texttt{ipole}$-based radiative transfer code, to enable gradient-based analyses of images generated from state-of-the-art general relativistic magnetohydrodynamic (GRMHD) simulations. We compute image sensitivities, i.e., pixel-wise derivatives of the intensity with respect to model parameters, which form the Jacobian of the forward model and define a local map from parameter space to image space. Using these sensitivities in a mock data analysis, we find that GRMHD-based images generate a structured error landscape for parameter fitting, with anisotropies and local minima, making parameter exploration nontrivial but still tractable when guided by gradient information. We characterize this landscape through the Jacobian and assess the feasibility of gradient-based recovery under idealized, blurred, and noisy conditions. Our results show that automatic differentiation-computed image gradients can guide parameter exploration effectively even in the presence of noise. These findings establish a basis for efficient, high-precision model--data comparisons in black hole imaging and motivate the integration of these sensitivities into advanced inference frameworks.

We investigate the possibility of a binary supermassive black hole system at the center of MCG+11--11--032, a local (z = 0.036) Seyfert 2 galaxy. Prior work with stacked Swift/XRT spectra suggested the presence of two Fe K$\alpha$ lines (at 6.16 keV and 6.56 keV) with 2$\sigma$ confidence. This could be consistent with a prediction of several hydrodynamical models, in which each black hole hosts a mini-disk and contributes one Doppler-shifted Fe K$\alpha$ line to the total spectrum. Another study using a single exposure from Chandra/ACIS did not find evidence for a double line. Here, we conduct follow-up with two epochs of XMM-Newton/EPIC data spaced $\sim$6 months apart. After fitting our spectra with models from the previous two studies, we do not find evidence for a double iron line in either observation. Our best-fit model yields $\Gamma = 1.63^{+0.20}_{-0.21}$ and $N_\text{H}/10^{22} \text{ cm}^{-2} = 17.9^{+2.7}_{-2.4}$ for the first epoch, and $\Gamma = 1.46^{+0.22}_{-0.24}$ and $N_\text{H}/10^{22} \text{ cm}^{-2} = 17.1^{+2.7}_{-2.4}$ for the second. We compare our spectral parameters with those derived in past work on this source, finding broad agreement with prior datasets. Lastly, we discuss the properties of MCG+11--11--032 alongside samples of Seyfert 2 galaxies from the literature, finding that it is consistent with this population and the single AGN scenario.

Relativistic jets launched by active galactic nuclei are fundamental for understanding the physics of accreting supermassive black holes and their immediate environment, yet the mechanisms driving jet launching remain uncertain. In this study, we investigate the sub-parsec jet of 3C 84 using multi-epoch, multi-frequency, very long baseline interferometry (VLBI) observations with the European VLBI Network and the Very Long Baseline Array at 22 and 43 GHz. We analyse the evolution of the spectral index gradient in the core region to relate the observed structure to physical interpretations and to discriminate between competing jet launching models. Furthermore, we examine the impact of the ambient medium and magnetic field configuration on jet morphology and dynamics over time, and explore their connection to a coinciding $\gamma$-ray flare. Our spectral analysis reveals significant changes across three epochs, indicating dynamic activity between filamentary structures on sub-parsec scales, evolving magnetic fields, and a complex interaction with the surrounding medium, all of which shape the innermost jet and may influence its high-energy emission.

We present an Atacama Large Millimeter/submillimeter Array (ALMA) spectroscopic follow-up survey of an 870 $\mu$m-selected sample of dusty star-forming galaxies (DSFGs) in the GOODS-S field. We use these linescans to identify or confirm spectroscopic redshifts (spec-zs) for 20 sources. Including spec-zs from the literature, there are now secure or tentative spec-zs for 52 out of 75 DSFGs (69%). At $f_{870}>2.5$ mJy, the sample is 97% spectroscopically complete, allowing us to model the full DSFG redshift distribution down to nearly the confusion limit for a 15-m telescope at 850 $\mu$m. This is the highest completeness for an unbiased sample at this flux limit to date. We find that nearly all of the DSFGs in our sample that were targeted with JWST/NIRSpec were spectroscopically identified, without much dependence on near-infrared or submillimeter flux or redshift. However, only 29% of our sample have JWST spectroscopic coverage. We use the spec-zs to evaluate various photometric redshift (photo-z) estimates, finding that all methods exhibit an outlier fraction of at least $>20$%. Nearly all of the photo-z methods tend to overshoot the redshifts, leading to overestimates of the number of DSFGs at high redshift ($z>4$). Our results suggest that $\lesssim10$% of $f_{870} \gtrsim 2$ mJy DSFGs lie at $z>4$ and $\lesssim2$% lie at $z>5$, reflecting a steep decline in the abundance of massive dusty galaxies in the first 1.5 Gyr.

Galactic radio transients (GRTs) are mysterious short-lived (~days to months) radio transients that are quiet at all other wavelengths. Until now, roughly half a dozen such sources have been reported, predominantly towards the Galactic center. However, no unifying properties have been identified among these, leaving their nature, emission mechanism, and even classification poorly understood. Due to the lack of periodic and uniform radio observations over wide areas of the Galactic plane until now, the sample size of such transients remained limited. Here, we use radio observations from the Australian SKA Pathfinder's Variables and Slow Transients survey to discover six new radio transients along the Galactic plane that resemble GRTs. Detailed investigation of archival data suggests that these sources may be divided into two classes: sources that exhibit sporadic, pulse-like (minutes) radio emission, and sources that exhibit long-term (weeks) flaring-type radio emission. For the short-time variable sources, we draw similarities between optically bright long-period radio transients and our sample to propose wide-orbit (~days) white dwarf binaries as underlying sources. For sources that show long-term outbursts, we draw comparisons between dust-obscured outbursts from WD binaries and our sample. These results could imply that the ongoing wide-field radio surveys are uncovering radio emission from sub-populations of WD binaries that were previously unexplored.

The multiply imaged SN 2022riv was discovered through a search of galaxy cluster fields as part of a Hubble Space Telescope (HST) SNAP program to find highly magnified stars. The supernova (SN) was detected in the last-to-arrive image of a galaxy at redshift $z=1.522$ strongly lensed by the foreground galaxy cluster RX J2129.7+0005. Follow up James Webb Space Telescope (JWST) NIRSpec G140M and PRISM spectroscopy yields a Type Ia SN classification. Using the SALT3-NIR light-curve fitter, we obtain a cosmology-independent measurement of the magnification of $5.35\pm1.01$ for the last-to-arrive image of the SN, with multiple SALT SN spectral time-series models yielding consistent constraints. The last-to-arrive image of SN 2022riv we detect appeared adjacent to the brightest cluster galaxy (BCG) at a location with an exceptionally high stellar mass density ($\sim 1-2$ dex higher than that of SN Refsdal), where microlensing is expected to introduce a 20-50% modulation of the magnification. Analyzing six independent lens models of the cluster, we find that four predict the magnification with much greater precision ($p < 0.05$) than would be expected by random chance, given the large effect anticipated from microlensing. Five models yield magnifications of roughly $4-7$ (within $1\sigma$) prior to accounting for microlensing, whereas HoliGRALE favors a significantly higher value of $15.39 \pm 0.85$. After incorporating nominal microlensing, the HoliGRALE prediction is within $1\sigma$ tension with our measurement. A companion paper (Dalrymple et al.) will present constraints on the relative time delay of the image that arrived earlier.

Recent analyses combining DESI DR2 BAO with CMB and SNe Ia data have reported $2.8$--$4.2\sigma$ evidence for dynamical dark energy, but the significance depends strongly on the supernova sample, raising the question of whether this signal reflects new physics, dataset-specific systematics, or the choice of dark energy parameterization. We investigate this question by analyzing four SNe Ia compilations (Pantheon, Pantheon+, DES-Dovekie, and Union3) with DESI DR2 BAO and Planck CMB distance priors, using flux averaging, model-independent expansion rate extraction, parametric ($w_0 w_a$CDM) fits, and a non-parametric reconstruction of the dark energy density ratio $X(z) \equiv \rho_{\rm DE}(z)/\rho_{\rm DE}(0)$. Flux averaging reduces the $\Omega_m$ difference between SNe and DESI from ${\sim}2\sigma$ to ${\sim}1\sigma$ for Pantheon+ and DES-Dovekie. The reconstructed $X(z)$ for DESI DR2 + CMB + SNe is consistent with $\Lambda$CDM for Pantheon, Pantheon+, and DES-Dovekie except at $0.5<z<1$, consistent with Wang \& Freese (2026). The largest deviation occurs at $z=2/3$, reaching ${\sim}2.7\sigma$ for Pantheon+ but only $1.6$--$1.7\sigma$ for Pantheon and DES-Dovekie. The $X(z)$ for DESI DR2 + CMB + Union3 is consistent with these within $1\sigma$, but shows an additional $2.4\sigma$ deviation at $z=1/3$ besides the ${\sim}2.7\sigma$ deviation at $z=2/3$. Across all analyses, the departure from $\Lambda$CDM correlates with each dataset's $\Omega_m$ preference. We demonstrate that a pure $\Lambda$CDM universe with the measured $\Omega_m$ differences can reproduce the observed $X(z)$ pattern, providing a viable alternative interpretation of the observed $X(z) \neq 1$ pattern. Future surveys by Euclid and Roman with sub-percent $\Omega_m$ constraints will be essential to determine whether the signal reflects genuine dark energy evolution or residual inter-probe $\Omega_m$ inconsistencies.

Stellar abundances reveal non-monotonic [Y/Eu] and [Sr/Eu] evolution, a systematic decline with increasing [Eu/H] at low metallicity, a minimum at $[\rm{Eu/H}] \sim -0.3$ and then a rise at high metallicity. This behavior requires at least three distinct neutron-capture sources operating on different timescales. We develop a one-zone chemical-evolution model constraining their typical delay-times, rates, and yield ratios. Reproducing the observed $\rm{[Y/Eu]}$ and $\rm{[Sr/Eu]}$ sequences requires, a delayed $r$-process channel (most likely binary neutron-star mergers) dominating Eu production ($\gtrsim 95\%$ of total Eu). A prompt channel preferentially producing first-peak elements with minimal Eu, explaining the increasing [Y/Eu] at decreasing [Eu/H] below $[\rm{Eu/H}] \lesssim -2.5$; and delayed AGB $s$-process enrichment with delays greater than $t_{min} = 0.3-0.6$\,Gyr reproducing the late-time upturn in Y (Sr). Our model quantitatively reproduces all constraints, including the large $\Delta[\rm{Y/Eu}] \approx 0.6$ dex variation between the late-time rise [Eu/H] and the minimum value, the location of the minimum at [Eu/H] $\sim -0.3$ and late-time rise. The first-to-second peak yield ratios correspond to $[\rm{Y/Eu}] \approx -0.3$ (prompt) and $\approx -0.8$ (BNS mergers). The observed $\Delta[\rm{Y/Eu}]$ amplitude establishes a model-independent lower limit on the first to second peak yield ratio $\gtrsim 3.4$ between the prompt and delayed channels, ruling out models with similar prompt and delayed yield ratios. These results demonstrate that explaining the observed heavy-element abundance patterns requires multiple channels with distinct nucleosynthetic signatures and operational timescales, providing constraints on the relative rates, delay times, and yield patterns of candidate production sites.

The lopsidedness of galaxies is a commonly observed phenomenon, and through different studies, it has been observed that nearly 30% of galaxies show this phenomenon. In this work, we study morphological lopsidedness in both stellar and gas disks in the inner and outer regions using Fourier analysis techniques and compare the results for a sample of nearby galaxies with different morphologies and environments. Although lopsidedness can result from diverse factors like tidal interactions, gas accretion, and internal instability, recent studies suggest it is a common feature that is not solely reliant on rare events, and moderate lopsidedness most likely results from the disk's response to a lopsided dark matter halo potential. Assuming lopsidedness originates due to a lopsided halo, we find the morphological and kinematic halo perturbation parameters in the same radial range. Unlike previous studies, we use 3D kinematic modelled rotation curves for finding kinematic lopsidedness and, hence, kinematic halo perturbation parameter. Although the detected linear correlation between them is not statistically significant for our small sample of eleven galaxies, this approach provides a more uniform and physically consistent framework to test the theoretically expected similarity between morphological and kinematic halo perturbation parameters. Further, within this framework, the discrepancy between them does not appear to depend on the nature of the rotation-curve asymmetry of the two sides of the galaxy, in contrast to trends seen in earlier studies. In future work, we plan to extend this analysis to a substantially larger sample in order to robustly assess these findings.

Polarized emission from dust and synchrotron radiation from the ISM are the dominant foregrounds for CMB polarization and are a major challenge for extracting the primordial signal on large angular scales. A key characteristic of the galactic foreground emission is its $EE/BB$ ratio. We argue that MHD shocks play an important role in setting the observed $EE/BB$ ratio. To support this, we first analyze quasi-linear magnetohydrodynamics (MHD) simulations to obtain an $EE/BB$ ratio that increases as $\sim k^2$, then show that with increasing energy injection rates, the $EE/BB$ ratio flattens to a value $\gtrsim 1$, approaching observational results. Looking at the distribution of the velocity divergence, a tail with power law $-7/2$ develops around the same injection rates where the $EE/BB$ ratio flattens. While the system becomes more isotropic, MHD shocks are intrinsically anisotropic and lead to the $E/B$ power asymmetry. We also observe total pressure balance among all our simulations, indicating slow wave dominance. Therefore, in the regime we consider, it is important to go beyond linear MHD equations to understand the foreground radiation.

Understanding how galaxies ignite and extinguish their star formation remains a cornerstone question in modern astrophysics. Recent JWST surveys have revealed an overabundance of massive quiescent galaxies in the first billion years of the Universe, challenging current models of galaxy evolution. In the nearby Universe, ram pressure stripping (RPS) is a major environmental mechanism capable of rapidly shutting down star formation, yet direct observation remains scarce at redshift $z\gtrsim1$, and its role at $z>2$ is even poorly constrained by simulations. Here, we utilize JWST and ALMA observations to present direct evidence of RPS in the post-starburst galaxy A2744-JF-z3, residing in a galaxy group at redshift 3.06, the earliest such detection to date. Spectroscopic diagnostics and spectral energy distribution modeling reveal the ongoing removal of cold gas and dust, coincident with the abrupt cessation of star formation. Contrary to hydrodynamical simulations that predict a reduced incidence of RPS at high redshift, our results instead imply that RPS can operate at $z>3$, suggesting a highly stochastic and impulsive stripping within a clumpy, filamentary intra-group and circumgalactic medium. These observations extend environmental quenching well into the epoch of galaxy assembly, highlighting RPS as a previously overlooked decisive pathway to rapid quenching in nascent groups and protoclusters in the early Universe.

Cosmic ray (CR) transport is usually modeled with a single diffusion coefficient, but this description captures only the growth of the variance and not the full transport process. Distinct transport mechanisms can share the same effective diffusion coefficient while producing different particle distributions and approaches to the diffusive limit. This limitation is especially relevant in realistic multiphase, structured, and time-dependent media, and is also reflected in observed environmental variations in CR transport near pulsar wind nebulae, supernova remnants, and molecular clouds. Particle-tracing studies also show clear departures from standard diffusion, including both superdiffusion and subdiffusion. We therefore develop a propagator-based framework centered on $P(x,t)$, the probability distribution of particle positions, or equivalently its Fourier-Laplace transform $P(k,s)$. This object is compact and statistically complete, and naturally exposes memory: the CR flux can depend on earlier gradients when unresolved trapping or phase changes are coarse-grained away. Using the Montroll-Weiss formalism, we show how to measure $P(k,s)$ directly from trajectories, how to recover the associated memory kernel, and how to represent broad kernels efficiently with a Prony expansion. Applied to a multiphase medium, the framework shows that slow regions can regulate escape without dominating the total residence-time budget. We also introduce an accelerated Monte Carlo method for coarse-grained transport, and show that if trapping structures evolve while particles are still sampling them, the static long-time limit need not be reached. This paper provides the foundation for future observational applications, particle-tracing measurements, and CR-MHD closures.

JWST has revealed an overabundance of very bright, blue galaxies at z>10, raising fundamental questions about how star formation and feedback operate at Cosmic Dawn. We present new JWST/NIRSpec MSA PRISM/CLEAR spectroscopy of JADES-GS-z14-0 (z=14.18) obtained with the JADES and OASIS programmes. While the rest-frame UV continuum flux level and shape are consistent between the two datasets, the OASIS spectrum shows a 10$\sigma$ detection of the CIII]$\lambda\lambda1907,1909$ emission line, with a luminosity three times higher than that measured in the JADES data. This difference is naturally explained by the offset in shutter placement between OASIS and JADES, implying that the CIII] emission is spatially displaced by $\sim400$ pc from the stellar continuum. The non-detection of CIII] in NIRCam medium-band imaging indicates that the emitting region is extended on scales $\gtrsim165$ pc, with a surface brightness below the detection threshold. Interpreting this diffuse, carbon-enriched gas as the result of ongoing or past outflows, we infer a mass outflow rate of $\dot{M}_{\rm out}\sim160~{\rm M_\odot\,yr^{-1}}$. We compare it with the star-formation rate (SFR) and derive a mass-loading factor of $\eta = \dot{M}_{\rm out}/{\rm SFR} = 4-15$, suggesting highly efficient feedback at very early times. Finally, we show that, if outflows are one of the mechanisms regulating star formation in JADES-GS-z14-0, the instantaneous star-formation efficiency in massive haloes is constrained to $\epsilon_\star\lesssim0.08$. These results support a scenario in which outflows play a crucial role during the earliest phases of galaxy formation. Comparing our results with the current theoretical galaxy formation model, we conclude that a combination of moderate star-formation efficiency and reduced dust attenuation can account for the emergence of luminous galaxies at the highest redshifts.

In this second paper in a series dedicated to characterizing shear layers via 2D hybrid (kinetic ions -- fluid electrons) simulations, we study the dynamical role of nonthermal particles (cosmic rays, CRs), either spontaneously generated or pre-existing. We initialize Kolmogorov-type sinusoidal velocity shear flows unstable to the Kelvin--Helmholtz instability, which evolve nonlinearly into turbulence. Particles with large gyroradii act as long-range messengers that promote momentum exchange between layers, hence introducing a form of CR viscosity. Even when not energetically dominant, increasing the CR energy density generally enhances momentum transfer, provided that their gyroradii are smaller than the shear lengthscale. We consider flows ranging from subsonic to supersonic and assess the rate of shear dissipation, the partition of the initial kinetic energy among heating, thermal ion acceleration, CR reacceleration, and magnetic-field amplification, and the maximum energy attained by accelerated particles.

We introduce a new kinematic disturbance parameter, $\Delta V_{\star-g}$ (pronounced `DVSG'), which takes advantage of integral field spectroscopy (IFS) to quantify differences between a galaxy's stellar and gas velocity maps. The motivation behind $\Delta V_{\star-g}$ is to capture disturbances in the kinematics of a galaxy that might be missed by alternative methods, while also attempting to minimize bias towards galaxy properties or features of the IFS data. We first detail the reasons for introducing this parameter, and explain how the $\Delta V_{\star-g}$ value of a galaxy can be calculated. We then present initial results using $\Delta V_{\star-g}$ to quantify the kinematic disturbance of obscured active galactic nuclei (AGN) found in the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. We find that there is no statistically significant difference between the $\Delta V_{\star-g}$ distributions of AGN and a control sample (matched in mass and redshift) of inactive galaxies. This suggests that AGN triggering may not be preferentially caused by any distinct kinematic disturbance process, or combination of processes, beyond those observed in inactive galaxies.

We summarise the properties and nature of a peculiar group of B-type stars called FS CMa stars. These stars show the B[e] phenomenon, i.e., their spectra exhibit both forbidden emission lines and infrared excess. Such properties point to an extended circumstellar gas and dust component. Although the phenomenon has been explained in most B[e] stars, the origin and nature of FS CMa stars is disputed. Here, we focus on the merger hypothesis, for which evidence has recently been discovered.

We anticipate that hundreds of thousands of distant, strongly gravitationally lensed sources will be detectable with the European Space Agency's (ESA) Euclid mission and the Rubin Observatory Legacy Survey of Space and Time. We consider the virtues and shortcomings of the Singular Isothermal Elliptical Potential (SIEP) with Parallel External Shear (XS_||) for these systems. Its principal virtue is that it admits an analytic forward model that gives image positions and magnifications as functions of the source position (and shape for extended sources). Preliminary experiments suggest a speed-up of a factor in excess of 10,000 compared with conventional models that instead map from the image plane to the source plane and require iteration to converge upon a unique source. A second virtue is that the Witt--Wynne geometric representation of SIEP+XS_|| permits the quick visual verification of the model's adequacy for a particular lensed system. Unfortunately, the model's strictly elliptical lens equipotential is inconsistent with strictly elliptical surface mass density contours. The Witt--Wynne construction might nonetheless yield a sufficiently good first approximation to accelerate convergence to one's preferred lens model.

'Lava worlds'-Earth-sized planets hot enough (Teq >~ 1100 K) to melt their dayside silicate surfaces-have emerged as promising candidates for atmospheric detection and characterization. Thermal emission observations show an apparent dichotomy: the hottest lava worlds have colder daysides than the temperature of a maximally emitting bare rock, indicating the likely presence of thick and/or reflective atmospheres while the coldest ones do not. However, where in instellation flux this potential bifurcation occurs is uncertain. We present a JWST MIRI LRS eclipse of the ultra-short period (USP) lava world HD 3167 b (Teq = 1786 K, R = 1.6 Rearth, P = 0.96 d) that helps bridge this gap. We measure the white light eclipse depth to be 38 +/- 11 ppm, more than 5 sigma lower than the expected eclipse depth of a dark, maximally hot bare rock. We use this to derive a dayside brightness temperature that is best explained by the presence of an atmosphere that cools the dayside by reflecting incoming starlight and/or efficiently redistributing heat to the planet's nightside. An atmosphere is further compatible with the planet's slight under-density compared to an Earth-like composition. The corresponding dayside emission spectrum is not precise enough to constrain atmospheric composition, motivating follow-up spectroscopic observations with JWST NIRSpec. Lastly, we use our observation and existing data to refine key planetary parameters of the HD 3167 system. HD 3167 b is currently the least irradiated USP super-Earth with evidence for an atmosphere.

Recent population-level studies of sub-Neptune atmospheres have identified a parabolic trend in transmission spectrum amplitude for planets with Teq ~ 500-800 K. While the trend has been commonly attributed to hydrocarbon aerosols, we lack a first-principles explanation of its underlying chemical mechanism. Previous work has focused on the role of methane photolysis and subsequent polymerization, but with limited reaction networks that truncated at C2-species and couldn't reproduce the observed parabolic trend. In this work, enabled by a computer-automated, rate-based chemical network generator, we construct the most comprehensive carbon reaction network for exoplanet atmospheres to date. We explicitly model the formation of polycyclic aromatic hydrocarbons (PAHs), which are well established as soot precursors in combustion chemistry. We calculate the chemical timescales of hydrocarbon species through an eigenvalue timescale method and model their quenched abundances across a range of C/O, metallicities, and Teq. In this framework, the deep atmosphere acts as a "soot factory" analogous to a combustion engine, transporting the ingredients for hydrocarbon aerosol formation to the JWST-observable region of the atmosphere, where it may be further augmented by photochemistry. We find that the predicted abundances of PAHs peak near 600 K, and fall off toward higher and lower Teq, in agreement with the observed parabolic trend and existing JWST and HST observations. We also show that PAH abundances are expected to vary with C/O and metallicity, thus providing a natural explanation for observed diversity among planets with similar Teq.

In protoplanetary discs, the presence of dust traps can significantly alter the transport of solids from the outer to the inner regions, and hence they are often invoked as an explanation for the chemical diversity of inner discs observed with JWST (e.g., varying oxygen abundances and C/O ratios). As a detailed treatment of dust transport around dust traps is computationally expensive, earlier works investigating the impact of outer traps on the inner disc composition have often used simplified dust models representing the size distribution with a single effective size and drift speed. In this paper, we revisit the impact of outer traps on dust transport using the state-of-the-art one-dimensional dust evolution code \texttt{DustPy}, which simulates the transport and evolution of dust particles including detailed coagulation and fragmentation. We quantify and map the leakiness of dust traps across a broad parameter space, performing over 300 simulations while varying the disc viscosity, turbulence strength, planet mass and location, and dust fragmentation velocity. We find that dust traps are leakier than previously thought, on a broader parameter space, such that most outer traps (r > 5 au) will result in a long-lived O-rich inner disc with gas-phase C/O < 1. In similar conditions (e.g., carved by the same planet mass), we find inner traps are much leakier than outer traps, though their relative efficiency in reducing the pebble flux is time-dependent. Highly blocking traps altering the inner disc composition dramatically (leading, e.g., to C/O > 1) are possible to set up but necessitate low viscosity and weak turbulence, along with efficient planetesimal formation by the streaming instability. In that case, we find that is the formation of planetesimals, rather than the dust traps themselves, that is capable of significantly altering the inner disc composition.

Massive quiescent galaxies (QGs) at high redshifts are likely progenitors of massive elliptical galaxies in the local Universe. Recent observations, such as the discovery of QGs in overdensity (galaxy groups and proto-clusters) at high redshifts, have highlighted the importance of the relationship between star formation activity in galaxies and the surrounding environment. We spectroscopically confirm a galaxy group associated with a massive QG at $z_\mathrm{spec}=4.53$ from the Lyman break feature using Subaru/FOCAS. This group consists of at least three star-forming galaxies within 150 pkpc of the QG, which suggests the importance of physical association with other galaxies for galaxy quenching. In order to understand the role of the surrounding environment, we also perform a statistical analysis to characterize the typical environment of QGs at high redshifts. By selecting QGs using the SFR-based selection in the COSMOS field, we find that the fraction of QGs is higher in group or cluster-like environment at $1<z_\mathrm{phot}<5$. This means some of the processes that regulate galaxy quenching occurs more frequently in the overdensity regions. In particular, the elevated fraction of QGs within small-scale overdensities ($<100\mathrm{-}300$ pkpc) at $z>2$ demonstrates that environmental quenching (primarily driven by galaxy mergers and interactions) plays a major role in the formation and evolution of massive QGs at high redshifts.

RR Lyrae stars are widely considered tracers of ancient (greater than 10 Gyr), metal-poor stellar populations. However, recent kinematic and photometric studies suggest the existence of a metal-rich RRL sub-population associated with the thin disc and intermediate ages (approximately 2-5 Gyr), challenging canonical evolutionary models. We aim to provide the first spectroscopic confirmation of a member of this elusive population. Specifically, we target a metal-rich RRL candidate recently identified photometrically as a member of the intermediate-age open cluster Trumpler 5. We obtained high-resolution spectroscopy using PEPSI at the LBT and GHOST at Gemini-South Telescope. We measured radial velocities from multiple epochs to constrain cluster membership and derived detailed chemical abundances (Mg, Ca, Sc, Ti, Mn, Fe, Cu, Zn, Y, and Ba) to compare the RRL's composition with that of red clump stars in the cluster. The RRL's systemic velocity Vgamma = 50.57 +0.78/-0.36 km/s is in excellent agreement with the cluster mean V = 50.76 +/- 0.49 km/s. Combining RVs, proper motions, and parallax, the probability of the star being a background interloper is negligible (approximately 0.002%, better than 4 sigma). We derived a metallicity of [Fe/H] = -0.40 +/- 0.05, matching the cluster value. While most abundance ratios (Mg, Ti, Mn, Cu, and Zn) align with cluster members, the RRL exhibits significant depletion in Ca, Sc, Y, and Ba. Notably, [Sc/Fe] is under-abundant by approximately 0.6 dex relative to the cluster stars, following trends seen in field metal-rich RRLs. We provide strong constraints on the membership status between an RRL variable and an intermediate-age open cluster [...]

Phylogenetic methods, traditionally used in biology to trace the evolutionary relationships among species, are emerging as a powerful framework to reconstruct evolutionary processes in galaxies from chemical information. We apply galactic phylogenetics to study the chemical evolution of stellar populations in distinct regions of a simulated disc galaxy, assessing its capability to unveil assembly histories. We used a high-resolution simulation that follows the chemical enrichment of an isolated disc galaxy, by different stellar progenitors. We track gas particles as they turn into stars and inherit their parent gas chemical composition. Target particles are selected to store the chemical history of each chemical element considered in the simulation. Two regions were analysed: an inner ring, influenced by early bar-driven inflows, and an outer ring, shaped by spiral arms. We built phylogenetic trees for stellar populations in each region and quantified their structure using the Corrected Colless index, a standard metric of tree balance used in biology. The inner ring tree reveals a compact clade of old stars enriched by rapid SNII feedback, followed by a hierarchical sequence with increasing SNIa and AGB contributions. In contrast, the outer ring exhibits more symmetric, caterpillar-like trees with smoother abundance gradients, consistent with more prolonged star formation and efficient local mixing. Chemical enrichment rates corroborate these trends, showing fast early enrichment in the inner ring and gradual, spatially extended enrichment in the outer disc. The structural indices differ significantly between the two regions and converge robustly even for modest stellar samples (NSSP = 100). Galactic phylogenetics provides a novel and complementary tool to decode the fossil record of galaxies.

With n-body simulations and analytic approximations we study the dynamics and stability of low eccentricity misaligned test particles around binary systems with varying mass fraction and eccentricity. General relativity (GR) plays a primary role in determining the motion of an outer particle since it drives apsidal precession of the binary orbit. The effects of GR can drive particle instability close to the binary orbit, depending upon the binary parameters and the initial inclination of the particle. For the binary parameters we consider, we find instability up to a semimajor axis of about 8 ab, where ab is the binary semimajor axis. In particular, we identify and analyse three different regions of instability that are driven by GR in the phase plane of the initial semimajor axis and the initial inclination of the particle. The results have implications for circumbinary orbits and circumbinary disks on all scales, but are particularly important around supermassive black hole binaries where the effects of GR can be strong.

OB runaway stars are massive stars moving through interstellar space at high velocities (up to 200 km/s), produced by dynamical ejections in young massive clusters or supernova explosions in massive binaries. They can travel several hundred parsec before exploding as supernovae, affecting the dynamical and chemical evolution of the Galaxy. The Vel OB1 association, one of the largest OB associations, hosts about 20 O-type and more than 50 B-type stars. We aimed to identify OB runaways in this region, quantify their number, identify their parent clusters, and understand their production channels and impact on the surrounding medium. Using Gaia DR3 coordinates, parallaxes, and proper motions, we identified OB runaways by measuring their peculiar velocity. We inspected infrared WISE images to identify wind bow shocks and reconstructed runaway trajectories to locate parent clusters and estimate travel times. We identified six young stellar clusters hosting most of the massive-star population in Vel OB1 (distance 1.6-2.1 kpc; age 1-10 Myr) and derived a threshold velocity of 15 km/s to classify runaways. We identified 25 OB runaways (including HMXB VelaX-1) and one F-type runaway. We detected 16 arc-like features, six associated with runaways selected by peculiar velocity, and ten bow shocks aligned with runaway proper motions. Parent clusters are identified for seven runaways, most likely ejected dynamically. The runaway fraction is about 30%. Wind bow shocks from OB runaways reveal valuable information on local ISM conditions.

We discuss the effective field theory of large scale structure in terms of a single scalar degree of freedom, corresponding to the velocity potential of the matter fluid in a $\Lambda$CDM universe. This cosmic ``pion'' field is nonlinearly related to the overdensity and the gravitational potential, and corresponds to the Goldstone boson of spontaneously broken spacetime symmetry, allowing us to organize perturbation theory in a systematic way while keeping the symmetries manifest. We develop the effective field theory of the pion field to next-to-leading order, and we use it to calculate the corrections to the power spectrum and to check that these are consistent with the consistency relations of spontaneously broken spacetime symmetry. We compare our results against computer simulations for the evolution of large scale structure in the pion field picture, and we make use of N-body simulations to measure EFT coefficients and analyze the growth of additional degrees of freedom in the deep nonlinear regime. We conclude with a discussion of how the pion field picture may help suggest new variables for analyzing simulations and experimental surveys of large scale structure.

Cosmology is living through fascinating times, where new observations from ground and space telescopes are questioning the established paradigm, the so-called Lambda Cold Dark Matter model. The particle nature of Dark Matter is severely constrained by underground experiments, while recent observations by galaxy surveys indicate that the cosmological constant (Lambda) may not be constant after all. Furthermore, observations at high redshift of fully-formed galaxies with massive black holes at their centers by the James Webb Space Telescope, as well as black holes with unexpected properties observed by gravitational wave detectors LIGO-Virgo, are driving an in-depth revision of our assumptions in models of structure formation and the evolution of the universe. I propose to explore two new paradigms to account for Dark Matter and Dark Energy, based on known physics without the need for new particles nor new degrees of freedom. I will extend the primordial spectrum of fluctuations to small scales with new statistical properties to provide a viable Primordial Black Hole scenario for Dark Matter, and will include non-equilibrium thermodynamics in the expanding universe, in the form of General Relativistic Entropic Acceleration, to explain Dark Energy. My proposal could provide a unified explanation for a plethora of interrelated multi-epoch, multi-scale and multi-probe observations from present and future Gravitational Wave detectors, Large Scale Structure observatories and Cosmic Microwave Background experiments. It emphasizes the need to develop new theoretical ideas hand-in-hand with observations to acquire a deeper understanding of our universe. If these ideas are correct, they will open a new window into the early universe and a new fundamental understanding of gravity in the late universe.

We investigate the current viability of a well-known coupled dark energy scenario in which fermionic cold dark matter (DM) interacts with a spin-0 dark energy component through a non-trivial field dependence of the DM mass. This ultra-light scalar mediates a fifth force between DM particles, which can leave signatures on cosmological scales. We use state-of-the-art data on the cosmic microwave background from Planck's CamSpec likelihood, baryon acoustic oscillations from the second DESI data release as well as the supernovae of Type Ia (SNIa) from Pantheon+ and DES-Dovekie. We perform the analysis considering both a flat potential and a Peebles-Ratra (PR) potential for the scalar field in order to assess the impact of the potential slope on the fitting performance of the model. While for a constant potential the scalar field dynamics is insensitive to the sign of the coupling parameter $\beta$, the PR potential breaks the existing symmetry in the solutions at late times and could induce a difference at the phenomenological level between positive and negative values. We study for the first time if it is actually the case, finding no important asymmetry in the fitting results. In the light of the aforesaid datasets, we find in all cases a peak at $|\beta|\sim 0.03$ - less pronounced than reported in some recent works -, excluding the no-coupling scenario at $\sim 95\%$ CL. The model is able to explain an effective crossing of the phantom divide, with the equation-of-state parameter lying within the $2\sigma$ bands of model-agnostic reconstructions. Our results are very robust under changes in the SNIa sample used in the analysis and is not significantly altered when we replace a constant potential with the PR one, although the latter is crucial to produce the aforesaid crossing. In passing, we also provide constraints obtained with the PR potential in the uncoupled case.

Meteorites are classified as either non-carbonaceous- (NC) or carbonaceous (CC), representing bodies that likely formed in the inner- or outer solar system, respectively. Despite its location in the inner solar system, the Earth is thought to contain either minor- (~6 %) or substantial amounts (~40 %) of outer solar system material. However, because neither interpretation leverages variations among multiple isotopic systems simultaneously, Earth's provenance remains equivocal. Here, we examine variations in 10 nucleosynthetic isotope anomalies among planetary- and meteorite parent bodies to show that the linear extension of an array defined by NC bodies in any two isotopic anomalies always intersects the observed isotopic composition of the bulk silicate Earth to within 1 standard deviation. The Earth therefore formed exclusively from inner solar system material whose composition did not vary over the course of accretion and was, on average, unlike that of any chondrite. Extension of the NC array yields isotopic compositions for Mercury and Venus that are more extreme than for Earth, implying a spatial or temporal gradient during the formation of the terrestrial planets.

The jets and lobes of nearby radio galaxies are ideal laboratories to explore the spectral and dynamical evolution of the radio-emitting plasma that emanates from active galactic nuclei. Here, we present a high-resolution radio continuum study of the low-redshift (z=0.01713), Fanaroff-Riley I (FRI) radio galaxy 3C 449 performed by combining radio data at 145 MHz acquired with the LOw Frequency ARray (LOFAR) and archival Very Large Array (VLA) data at 1365, 1485, 4985, and 8485 MHz. Our LOFAR maps have angular resolutions of 20"x20" and 6.0"x6.0", and show the full extent of the known radio emission at the highest angular resolution to date. Our spectral index maps show the distribution of the spectrum in the 145-8485 MHz frequency range over a region that extends beyond 2.5'. The average 145-8485 MHz spectrum is consistent with a single power law and stays approximately constant over the inner ~50" of both jets. Beyond ~50", on both source sides, the higher-frequency spectrum steepens, indicating no significant downstream sites of particle acceleration. By modelling the spectrum under the assumption of equipartition and of a constant magnetic field across the source, we derive maps of the highest radiative age of the particles. At the outer edges of both the northern tail and southern lobe, the spectral age is ~150 Myr. If the latter age were representative of the dynamical source age, the average expansion speed of both jets during the source lifetime would be supersonic, with Mach numbers of M~4.1 and M~2.8 for the northern and southern jets, respectively. As numerical simulations of FRI jets suggest that the source's current expansion is subsonic, the high Mach numbers might arise either from the source being highly supersonic for a small fraction of its lifetime or from a severe underestimation of the spectral age due to particle acceleration on scales of hundreds of kpc.

Self-gravitating systems of $N$ particles are chaotic. We wonder how chaotic the Galaxy is, and what the consequences are. We therefore simulate the dynamical evolution of a galaxy-scale distribution of point masses in order to measure the degree of chaos in such a system. These calculations were performed using the softened gravitational $N$-body tree-code Bonsai, with up to 40 million equal-mass particles. Smaller simulations were performed to establish the scaling of the Lyapunov time $t_L$ with $N$. We establish the relations between the degree of chaos, the number of particles, and the softening length in the gravitational force calculation of large-scale $N$-body simulations. The moment the bar forms appears insensitive to infinitesimal perturbations to the initial realisation. In contrast, the bar strength and its further evolution sensitively depend on such perturbations. Interestingly enough, the run-to-run variation in the bar strength has its maximum around the maximum bar strength, and drops to the moment the bar buckles. The galaxies we simulated are highly chaotic, but the softening in the simulations suppresses chaos. Still, our models show considerable variations in the macroscopic behaviour due to infinitesimal perturbations to the initial conditions. Real galaxies, however, should be orders of magnitude more chaotic than our simulations, and we are unable to quantify their consequences. Smooth galactic potentials to study individual stellar orbits should be handled with caution on timescales longer than the Lyapunov time. Extrapolating to the number of stars in the Galaxy, ignoring planets and other minor bodies, we conclude that the Milky Way-size galaxies are chaotic on a timescale $\lesssim 0.1$ Myr.

Be/X-ray binaries, the most common class of high-mass X-ray binaries, are characterised by OBe companions, but display a rich variety of X-ray behaviours. One of the most atypical systems is X0726-260, which also has the earliest optical counterpart among the whole Milky Way and Magellanic Cloud sample. We intend to improve the characterisation of the optical counterpart, LS 437, and to constrain the physical mechanisms responsible for the anomalous properties of X0726-260. We analyse high-quality, high-resolution optical spectroscopy of LS 437 with standard quantitative methodology to derive stellar parameters. We also make use of archival X-ray monitoring. We derive a moderate projected rotational velocity v sin i $\approx$ 155 km/s and a spectral type O7.5 Ve (Teff = 36 000 K), which makes LS 437 substantially earlier than any other Oe star in an X-ray binary. At this spectral type, the stellar wind likely contributes significantly to mass accretion, and the X-ray light curve is strongly suggestive of an orbitally modulated wind accretor. The source shows marked carbon depletion, whereas nitrogen is only slightly above solar abundance. LS 437 is the earliest Oe star known in the Galaxy, alongside HD 155806. Long-term X-ray lightcurves of X0726-260 strengthen the identification of a persistent 34.5 d periodicity as the orbital period, demonstrating that the X-ray emission is orbitally modulated and no X-ray outbursts have occurred over the past 30 years. Likewise, emission features in the optical spectrum indicate a remarkably stable circumstellar disk, with no sign of major structural changes over the past 40 years. All these characteristics set X0726-260 clearly apart from typical Be/X-ray binaries.

Previous theoretical studies indicate that the inner disk in dwarf novae evaporates into a high-temperature, optically thin, and geometrically thick accretion flow during quiescence, with the inner edge moving toward the white dwarf at the onset of an outburst. We incorporate this process into the numerical model developed by Kimura & Osaki (2023) and test the code on two representative dwarf novae, SS Cyg and U Gem. By modeling the inner accretion flow, we calculate the optical, ultraviolet (UV), and X-ray luminosities. Our results show that evaporation suppresses the inside-out outbursts without requiring a radially dependent viscosity parameter in the cold state. The observed time delay between the rise in UV luminosity and the onset of the optical outburst is more than one day, which is successfully reproduced when the inner disk is truncated at several $\times 10^{9}$ cm in the standard evaporation model. However, while the modeled accretion rate at the inner disk edge in U Gem accounts for its quiescent X-ray luminosity, the rate in SS Cyg remains insufficient. This discrepancy in SS Cyg suggests that SS Cyg may require either more efficient evaporation or an additional mass supply into the coronal cavity via gas-stream overflow. By accounting for disk evaporation, our simulations offer a refined version of the disk instability model for dwarf nova outbursts that naturally explains the observed multiwavelength light curves.

The outgassing signatures of Io, Europa, Enceladus, Triton, and Io-like exomoons are the focus of this review chapter. The rocky volcanic world of Io is unique in our Solar System, with plumes reaching to hundreds of kilometres in altitude. Io-like exomoons could leave signatures strong enough to be detected with ground-based telescopes. The icy moons Europa and Enceladus, with their subsurface oceans, are currently the best candidates for life. Triton is different in many ways and raises unexplored questions. Our knowledge of these active moons is derived from space- and ground-based observations. To understand their origin, we discuss moon formation in general, before examining evidence and signatures of plumes on these moons. Given the accessibility of subsurface oceanic material through the occurrence of plumes, we expand on possibilities to investigate biosignatures.

Changing-Look AGN (CL-AGN) are AGN which transition between Seyfert types, challenging AGN unification models. Most CL-AGN have been identified via repeat spectroscopy, making it difficult to determine the duration and magnitude of the CL-AGN transition. As such, the physical mechanisms behind this transition are still unknown. We use synthetic photometry in combination with ZTF light curve data to develop a new criterion to identify photometric CL-AGN transitions based on changes in g-band magnitude and g-r color. We find that a CL-AGN criterion of $| \Delta g| > 0.4$ mag and $| \Delta (g-r)| > 0.2$ mag recovers a photometric transition in $9.6^{+4.9}_{-3.4}\%$ of CL-AGN hosts over the six-year ZTF survey, including a candidate repeating changing-look event in SDSS J084957.78+274728.9. Using simulated AGN light curves, we estimate the false positive rate among the simulated Seyferts to be $1.6^{+0.19}_{-0.17}\%$. We find that the rate of similar flares among Type 1 Seyferts is $1.2^{+0.87}_{-0.50}\%$ , and among Type 2 Seyferts is $\leq 0.39\%$ over six years. Photometric CL-AGN transitions last between 21 and 560 days, with a median duration of 360 days, consistent with the thermal or orbital timescales for AGN disks. We do not detect a correlation between black hole mass and transition duration, likely due to the small sample of detected photometric transitions. This method can be applied to the upcoming Legacy Survey of Space and Time to identify CL-AGN candidates and test theories of their origins

Turbulent mixing remains one of the primary uncertainties in the modeling of stellar interiors. In stellar evolution simulations, regions where mixing occurs are typically identified using instability criteria. A particularly interesting situation arises when nuclear reactions produce inversions in the mean molecular weight within stellar interiors. Under these conditions, the material can become unstable to either thermohaline or a Rayleigh-Taylor instabilities. We demonstrate that the standard criterion adopted in stellar evolution calculations does not accurately distinguish between these two regimes. We derive an alternative criterion and show that chemically driven convection in stellar interiors might be viable under much smaller mean molecular weight inversions than it is normally assumed. We investigate whether inversions in the mean molecular weight can trigger chemically driven convection above the red giant branch bump (RGBB) or during the helium core flash. We find that the inversion at the base of the convective envelope above the RGBB is too weak and short-lived to sustain steady-state convection. In contrast, rapid carbon production at the base of the He-flash-driven convective zone can maintain a steady chemically driven convective region. This process could significantly alter our understanding of the He-core flash and warrants further study.

We examine the positions of substellar objects in mid-infrared color-magnitude and color-color diagrams to distinguish between cloudy and cloud-free atmospheres. Using Spitzer mid-infrared spectra of 113 M5-T9 ultracool dwarfs, we derive synthetic photometry for the JWST MIRI F560W, E'770W, F1000W, and F 1280W filters, which cover key absorption features including the ~9 um silicate signa-ture. We find that diagrams involving F770W and F1000W best separate L-type objects with silicate clouds in their photospheres. L dwarfs with mE77ow - mF1000w < 0.03 mag are seven times more likely to host cloudy atmospheres. Diagrams using F1000W and F1280W are less informative due to the lower signal of the spectra at long wavelengths. Current model predictions struggle to reproduce the positions of cloudy, warm brown dwarfs, likely because atmospheric models underestimate the ~9 um silicate feature. Cloudy Sonora Diamondback models better match the observed trends, although this may reflect improvements capturing indirect effects of clouds on the 6.25 um water absorption feature rather than accurately modeling the silicate feature itself. Our analysis indicates that JWST MIRI photometry can efficiently identify new cloudy extrasolar atmospheres for targeted spectroscopic follow-up, optimizing the use of telescope time.

The 100,000-year problem concerns the dominant period of glacial-interglacial cycles over the past 800,000 years and their correlation with Earth's orbital eccentricity, despite eccentricity's weak influence on solar radiation. Two theories compete: the astronomical theory, in which orbital forcing drives the cycles with amplification from Earth system feedbacks, and the geochemical theory, in which internal dynamics dominate with orbital forcing synchronising oscillations. We investigate these theories using conceptual models. Augmentations to the Budyko energy balance model fail to reproduce the 100,000-year period, revealing formulation limitations. Linearised versions of existing non-linear ice volume models perform comparably to their full counterparts, indicating the data does not necessitate non-linear dynamics. We develop two simple linear models: a feedforward model aligned with the astronomical theory and a feedback model aligned with the geochemical theory. The feedforward model reproduces the ice volume record well and offers a novel explanation for the absence of eccentricity's 400,000-year period, arising from oceanic heat storage and tropospheric energy responding with differing phase lags. Conservative estimates show bulk ocean temperature variation can be explained by eccentricity alone, challenging the geochemical theory's core assumption. We also show that widespread use of Q65 may bias models towards geochemical explanations by underrepresenting eccentricity. The feedback model's improvement is concentrated around Marine Isotope Stage 11, suggesting this anomalous interglacial reflects Earth-based events rather than a general requirement for feedback mechanisms. We conclude that 800,000 years of glacial cycles can be largely reproduced by a linear astronomical model, emphasising the importance of parsimony when interpreting palaeoclimate data.

We model the dynamical mass density profiles of 14 strong gravitational lens galaxies from the Sloan Lens ACS (SLACS) sample using spatially resolved kinematics obtained from Keck KCWI integral-field spectroscopy. We use the Jeans Anisotropic Modeling (JAM) method, combining 2D kinematic maps with joint constraints from lens models from Hubble Space Telescope imaging. We use informative priors on the anisotropy and intrinsic shape from local galaxies to help break the residual mass-anisotropy degeneracy (MAD). We find nearly isothermal power-law total mass density slopes ($\rho_{\rm tot}\propto r^{-\gamma}$) for the sample with a mean of $\gamma = 2.04\pm0.02$ with intrinsic scatter of $0.08^{+0.03}_{-0.02}$. We fit explicitly for deviations from the pure power-law form that are fully sensitive to the mass-sheet degeneracy (MSD) and constrain the value of the mass-sheet parameter $\rm \lambda_{int}$ for each individual galaxy to an average precision of 5.8%. The mean value of $\rm \lambda_{int}$ for the sample is $1.01\pm0.03$, with intrinsic scatter of $0.11\pm0.03$. Values of $\rm \lambda_{int}$ for individual objects and the scatter in the sample are consistent to $1\sigma$ uncertainty with those found by the Time-Delay COSMOgraphy collaboration's 2025 milestone analysis, which used a spherical analysis of the same dataset, but azimuthally averaged. We thus conclude that on average power-law mass profiles are a good first-order description of the SLACS sample and do not introduce measureable bias in time-delay cosmography. However, our analysis indicates that more flexible mass models should be able to reproduce the highly detailed kinematic datasets more accurately.

Observations of ultra-dense substructures in strong lensing systems challenge the standard cosmological model at small scales. Self-interacting dark matter (SIDM), as an alternative to the cold and collisionless dark matter (CDM) of the standard cosmological model, provides a natural mechanism for forming such structures via gravothermal core collapse. We show that strong gravitational lensing of fast radio bursts (FRBs) provides an effective approach to detecting these substructures and probing dark matter self-interactions. Core-collapsed SIDM halos exhibit steeper central density profiles than CDM halos, enhancing the lensing cross section and producing longer time delays between FRB images. We compute lensing properties of core-collapsed subhalos and host halos, including maximal impact parameters and time-delay distributions. We demonstrate that future all-sky monitors, such as BURSTT, SKA2-Low, and SKA2-Mid, which are expected to detect $10^{5}$--$10^{7}$ FRBs over a decade, can measure time-delay distributions with high statistical significance. Modeling collapsed halos with a cored power-law density profile with inner slope $\gamma=3$ and assuming no excess beyond the singular isothermal sphere lens model, we show that our strategy can probe self-interaction cross section strengths of $\sigma_{\text{SI}}/m \gtrsim \min\{18,\, 40\lambda_{\text{sub}}\}\,\text{cm}^2/\text{g}$, where $\lambda_{\text{sub}}$ parameterizes the collapse time of a subhalo relative to that of the isolated case.

We present JWST/MIRI-MRS observations of ISO-Oph 37, a highly inclined flat-spectrum ($\lesssim$1 Myr old) source, to investigate the chemical composition and dynamical origin of its inner-disk gas. The spectrum reveals a rich combination of molecular emission and absorption: H$_2$O, CO, and OH are detected in emission, while strong absorption is observed from CO, H$_2$O, CO$_2$, HCN, C$_2$H$_2$, and CH$_4$, with no detectable ice absorption features. LTE slab modeling of the absorption yields excitation temperatures of $T_{\rm ex}\sim400-600$ K and column densities of $\log N/{\rm cm}^{2}\sim16-19$, characteristic of warm gas located within the inner few au. The absorption lines are significantly blueshifted relative to the systemic velocity, with mid-IR lines exhibiting larger shifts than near-IR CO absorption. This velocity structure points to a velocity- and temperature-stratified molecular disk wind. In this framework, the absorption directly samples disk material lifted from the inner disk surface, preserving the chemical imprint of the wind-launching region. Along the line of sight, ISO-Oph 37 is unusually hydrocarbon-rich compared to other known absorption systems (GV Tau N and IRS 46), exhibiting high (C$_2$H$_2$+CH$_4$)/HCN, (C$_2$H$_2$+CH$_4$)/CO and H$_2$O/CO column density ratios, while the CO and HCN columns remain broadly typical. We find that these molecular ratios are best explained by enhancement of both hydrocarbons and water, driven by inward drift and sublimation of icy pebbles and by thermal processing of carbonaceous grains at the soot line. ISO-Oph 37 thus demonstrates that carbon-rich inner-disk chemistry can be established early in disk evolution and that it can be directly probed through molecular absorption in disk winds.

We present a method of spatially mapping microwave kinetic inductance detector (MKID) arrays, in a dark setup. MKIDs are superconducting natively multiplexed resonators which enable kilopixel arrays, such as for the proposed Probe far-Infrared Mission for Astrophysics (PRIMA). In such telescope applications one must map the spatial location of each MKID with their individual resonance frequencies. Traditional LED arrays or beam-mapping methods become increasingly difficult as pixel spacing decreases, e.g., 900 {\mu}m separated MKIDs in the spectrometer module of PRIMA. Our new mapping technique uses a cryogenic interferometer in reflection mode. As on-resonance signals reflect from an MKID, they accrue a phase proportional to the path-length, exactly corresponding to their physical distance on the feedline. Specifically, we use a superconducting transmission line that has nonlinear kinetic inductance. The slow-wave structure of this nonlinear device is designed to have a signal speed of 0.64% the speed of light, enabling a compact system. Current biasing this line allows for varying the wave speed and ensuring that the phase measured is periodic within a nulling interferometric mode. Using this setup, we measure a length ordering that reflects the bimodal MKID distribution of a 44 pixel array of MKIDs designed for PRIMA which contains the same spacing as the final kilopixel array design.

The exponential growth of data from modern radio telescopes presents a significant challenge to traditional single-pulse search algorithms, which are computationally intensive and prone to high false-positive rates due to Radio Frequency Interference (RFI). In this work, we introduce FRTSearch, an end-to-end framework unifying the detection and physical characterization of Fast Radio Transients (FRTs). Leveraging the morphological universality of dispersive trajectories in time-frequency dynamic spectra, we reframe FRT detection as a pattern recognition problem governed by the cold plasma dispersion relation. To facilitate this, we constructed CRAFTS-FRT, a pixel-level annotated dataset derived from the Commensal Radio Astronomy FAST Survey (CRAFTS), comprising 2{,}392 instances across diverse source classes. This dataset enables the training of a Mask R-CNN model for precise trajectory segmentation. Coupled with our physics-driven IMPIC algorithm, the framework maps the geometric coordinates of segmented trajectories to directly infer the Dispersion Measure (DM) and Time of Arrival (ToA). Benchmarking on the FAST-FREX dataset shows that FRTSearch achieves a 98.0\% recall, competitive with exhaustive search methods, while reducing false positives by over 99.9\% compared to PRESTO and delivering a processing speedup of up to $13.9\times$. Furthermore, the framework demonstrates robust cross-facility generalization, detecting all 19 tested FRBs from the ASKAP survey without retraining. By shifting the paradigm from ``search-then-identify'' to ``detect-and-infer,'' FRTSearch provides a scalable, high-precision solution for real-time discovery in the era of petabyte-scale radio astronomy.

White-light flares (WLFs) are crucial for understanding the energy transport and heating processes in the lower solar atmosphere. Systematic studies are highly necessary. However, most WLFs are very weak and difficult to detect. To address this, we propose a new method of detecting WLFs. Through the observations of SDO/HMI, the light curve of each pixel in the flaring region can be obtained. By subtracting the slowly varying background, we obtained a series of rapidly varying radiative pulses. Pixels for which radiative pulses during flares significantly exceed those occurring before and after the flare were identified as WL emission regions. We applied our method to the detection of the X2.2 flare on September 6, 2017 and validated the method. We found that the WL emission in this flare exhibits two phases, and that different regions show distinct WL emission properties. We also detected the WL emission in all the flares (1 X-class, 2 M-class, and 20 C-class) occurred in active region NOAA 12887. It was found that 15 of the 23 flares are WLFs (1 X-class, 2 M-class, and 12 C-class). The occurrence rate of WLFs in this active region is $\sim65\%$. Surprisingly, the occurrence rate of WLFs in C-class flares even reaches up to $60\%$. It should be noted that most of these C-class WLFs are below C5.0. In addition, a C1.0 WLF was identified; this is the lowest GOES-class event with confirmed WL emission to date. These results demonstrate that WL emission is ubiquitous in most flares, even down to C-class events.

We report a photometric and asteroseismic analysis of KIC 3868420, a newly identified high-amplitude $\delta$ Scuti-$\gamma$ Doradus hybrid star located in the Hertzsprung gap - a short-lived and rarely observed post-main-sequence phase. Using four years of Kepler long-cadence photometry, we detect 36 significant frequencies, including 11 independent modes spanning both low- and high-frequency regimes. Grid-based modeling with MESA and GYRE, including rotation, shows that five independent frequencies match a combination of radial p-modes and non-radial g-modes, supporting its hybrid nature. The best-fit models yield an evolved post-main-sequence star ($M \sim 2.26 - 2.30 M_\odot$, $R \sim 4.41 - 4.43 R_\odot$, $\tau \sim 5.4 \times 10^{8}$ yr), although degeneracies from rotation and unknown inclination preclude a unique solution. KIC 3868420 thus represents a rare example of a high-amplitude hybrid pulsator in the Hertzsprung gap, demonstrating that high-amplitude pulsation can coexist with mixed p/g-mode behavior in a rapidly evolving star. This finding highlights the value of space-based photometry for identifying such rare objects.

We present a deep learning framework to enhance the identification of Ly$\alpha$ emitters (LAEs) in the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), an untargeted spectroscopic survey of LAEs at $1.9 < z < 3.5$ without imaging pre-selection. We primarily address the low signal-to-noise ratio (S/N) regime ($4.8 \leq \mathrm{S/N} \leq 5.5$), where LAE candidates suffer from substantial noise contamination. To distinguish LAE candidates from artifacts and sky residuals, we employ a convolutional neural network (CNN) trained on two-dimensional spectral images of single emission lines. The training sample is constructed from the HETDEX COSMOS catalog, with external validation from ancillary observations and our participatory science project, \textit{Dark Energy Explorers}. For small-format, low-resolution spectroscopic data, the model achieves a balanced accuracy, precision, and recall of $94.1\%$, $97.5\%$, and $97.5\%$, respectively, in the high-S/N regime ($\mathrm{S/N}>5.5$), and $85.1\%$, $78.2\%$, and $84.4\%$ in the low-S/N regime. Using HETDEX LAEs independently identified by DESI spectroscopy, the model recovers $99\%$ and $93\%$ of the high- and low-S/N LAEs, respectively. Visual attribution indicates that the CNN attends to smooth, spatially extended central emission in true positives and to irregular or noisy features in true negatives. Applied to the full HETDEX catalog, the CNN enables an S/N threshold down to 4.8 by suppressing spurious spikes across $z\sim 1.9$--$2.5$ in the redshift distribution. Our approach facilitates HETDEX cosmological analyses by mitigating false positives in galaxy clustering and highlights the value of domain-specific deep learning for refining low-S/N spectroscopic identification in untargeted surveys.

The physical origin of optical changing-look AGNs (CLAGNs), characterized by the appearance or disappearance of broad emission lines, is thought to be mainly driven by the variation of the black-hole (BH) accretion rate. In this work, we explore this issue based on a sample of {224} CLAGNs with UV-to-optical continua, where the UV radiation is more sensitive to the accretion state near the BH horizon. We find that the luminosity correlation of $L_{3000}$--$L_{5100}$ at 3000$\rm Å$ and 5100$\rm Å$ becomes steeper at low luminosities (e.g., $L_{3000}\lesssim10^{44}\rm erg/s$), where the sources with high luminosities are roughly consistent with the prediction of a standard accretion disk. At lower luminosities, the observations are more consistent with the prediction of a truncated disk. The whole sample has a median bolometric Eddington ratio of $\sim$2.2\%, which is consistent with the critical value for state transition in X-ray binaries. Such transitions can significantly alter the UV-to-optical continuum, largely due to variations in the truncation radius, even when the change in the overall accretion rate is minimal. The deficit of ionization photons resulting from an increase in the truncation radius will lead to the weakening or disappearance of broad lines, which triggers the AGN changing-look.

$\mu$ Herculis is a bright, nearby quadruple system. Its brightest member, $\mu$ Her Aa, displays solar-like oscillations, establishing the system as a crucial benchmark for asteroseismology, provided that its mass can be determined independently of stellar models. We aim to resolve the full hierarchical architecture of the system and determine precise, model-independent dynamical masses for all four components (Aa, Ab, B, and C), along with a consistent astrometric solution for the system's centre of mass. We performed a joint fit of radial velocities, relative astrometry and absolute astrometry from \textit{Hipparcos}, \textit{Gaia} DR3, and ground-based catalogues, spanning nearly three centuries. Our forward-modelling framework simultaneously constrains the Keplerian orbits of the inner Aa--Ab and B--C subsystems, the wide A--BC orbit, and the sky motion and parallax of the total centre of mass. Leveraging several complementary datasets and the decisive 2023 periastron passage of the Aa--Ab pair, we precisely determine all orbital parameters and obtain sub-percent precision on the component masses: $M_{\rm Aa} = 1.134 \pm 0.007\,M_{\odot}$, $M_{\rm Ab} = 0.2286 \pm 0.0006\,M_{\odot}$, $M_{\rm C} = 0.445 \pm 0.005\,M_{\odot}$, and $M_{\rm B} = 0.417 \pm 0.005\,M_{\odot}$. We derive a system parallax of $\varpi_{\rm CM} = 120.069 \pm 0.089\,\mathrm{mas}$ that reconciles and improves upon the individual \textit{Hipparcos} and \textit{Gaia} DR3 values.

We present a focused multiwavelength study of blue straggler stars (BSSs) in the intermediate-age open cluster Tombaugh 2, located in the outer Galactic disk, to constrain the dominant formation pathways of BSSs in a low-density environment. Cluster members are identified using Gaia DR3 astrometry through a Gaussian Mixture Model, yielding a clean sample of high-probability members. Color-magnitude diagram analysis indicates an age of 1.74 Gyr. The radial surface density profile is well described by a King model, indicating a centrally concentrated overall structure, while the cluster exhibits only weak or no clear evidence of mass segregation among its stellar populations. We identify 26 BSS candidates and 2 YSS candidates. Spectral energy distributions constructed from ultraviolet, optical, and infrared photometry reveal that 9 BSSs (32%) exhibit significant ultraviolet excess, indicating an additional hot component. Binary SED decomposition identifies stripped companions with effective temperatures Teff $\sim$ (1.5-8) $\times$ 10$^4$ K and radii R $\sim$ 0.04-0.28 R_$\odot$, consistent with proto-white dwarfs, extremely low-mass pre-helium white dwarfs, and young hot remnants formed through recent mass transfer. A slight central concentration of BSSs, together with stripped companions, suggests that binary mass transfer is an important formation channel, with no evidence for merger-driven formation. Multi-epoch VLT/FLAMES spectroscopy reveals radial-velocity variability in several systems, providing independent evidence for binarity. Our results highlight that optical-infrared photometric analyses alone may fail to detect hot compact companions, while spectroscopy and ultraviolet observations provide complementary constraints, with ultraviolet data offering a direct probe of such companions in intermediate-age open clusters.

We investigate whether the Type Ibn supernova SN 2023uqf, reported close in time and direction to the $\sim$442 TeV IceCube alert IC-231004A, is physically consistent with a shock--circumstellar medium (CSM) interaction scenario. One-dimensional radiation-hydrodynamics calculations with {\tt STELLA} reproduce the ZTF optical light curves with a dense helium-rich CSM following $\rho_\mathrm{CSM} \propto r^{-3}$ and a CSM density parameter $D'\approx 50$. Using the shock evolution and CSM conditions inferred from the optical data, we model time-dependent cosmic-ray acceleration and hadronic neutrino production during the interaction phase. The inferred shock and CSM properties open a short-lived window in which multi-PeV hadron acceleration and efficient hadronic interactions can coexist, making SN 2023uqf a plausible transient PeVatron candidate. After folding the predicted neutrino emission through the IceCube effective area, we obtain an expected number of $\sim10^{-5}-10^{-4}$ track-like events at $d = 723$ Mpc, depending on the alert selection. In the low-count regime, the model predicts a detection-time weighting for a rare event, and the detection time of IC-231004A falls within the high-weight interval while its energy scale is compatible with the modeled spectrum. Although a single event cannot establish a definitive association, our results show that the optically inferred environment of SN 2023uqf is consistent with a transient PeVatron window and illustrate how interaction-powered Type Ibn supernovae can be tested as high-energy neutrino sources.

Magnetic field amplification is an integral part of the process of particle acceleration at non-relativistic shocks. It is necessary to reach the maximum energies required by observations, especially in supernova remnants, thought to be sources of the bulk of Galactic cosmic rays. Such amplification can be caused by the acoustic instability that develops when small density perturbations interact with the cosmic-ray pressure gradient in the upstream of a cosmic-ray-modified shock. The vorticity induced by the nonlinear development of the instability may lead to turbulence, which amplifies the pre-existing magnetic fields. To study this phenomenon, we use the PLUTO code to carry out 2D (and some 3D) magnetohydrodynamical simulations of the evolution of small density perturbations in the presence of an assigned cosmic-ray pressure gradient. Adopting more realistic values of Mach number and cosmic-ray acceleration efficiency than previously assumed in the literature, we show that the acoustic instability can transform small density perturbations into large nonlinear structures while the fluid crosses the precursor region of a cosmic-ray-modified shock. We study the power spectrum of turbulent magnetic fluctuations that may be important to scatter particles. We comment on the possible constructive interference between acoustic and non-resonant streaming instabilities. We discuss limitations of previous and current numerical investigations in accessing spatial scales where turbulence is expected to turn nonlinear, and outline perspectives for future investigations.

The cubic-kilometer neutrino telescopes have opened neutrino astronomy as an observational discipline. The recent detection of KM3-230213A, the highest-energy neutrino ever observed at ~220 PeV, as a near-horizontal muon track underscores that the ultra-high-energy frontier is accessed through horizontal directions where the Earth's opacity above ~100 TeV confines the observable sky to a narrow band around and above the horizon. Yet extending general-purpose detector architectures into this regime requires disproportionate increases in instrumentation, cost, and logistical complexity. A compelling alternative is to deploy specialized detectors that target this natural geometry. POLARIS (Pacific Ocean Large Area Radial Instrumented Sparse array) is a sparse planar deep-water Cherenkov array optimized for neutrino-induced muon tracks from horizontal directions in the multi-TeV to PeV regime. By rotating the conventional vertical string layout into a radial planar configuration, the detector presents maximal cross-section to horizontal tracks while naturally suppressing the down-going atmospheric background. With only 1100 optical modules, the five-arm design reaches point source and diffuse flux sensitivities at PeV energies competitive with detectors deploying several times more instrumentation. As a dedicated $\nu_\mu$ track detector, POLARIS provides the muon-flavor channel that tau-optimized experiments such as TAMBO and Trinity do not cover, enabling full flavor composition measurements from astrophysical sources. Using the Prometheus simulation framework, this study demonstrates that targeted sparse geometries can open new discovery space at the high-energy frontier at a fraction of the cost of general-purpose arrays.

Variability is a well known phenomenon in low-mass young stellar objects, but in recent years the monitoring of methanol masers and infrared continuum emission has permitted the detection of both burst-like episodes and periodic variations also in high-mass (proto)stars. Multi-epoch studies on large samples of these objects have become possible thanks to the NEOWISE database, which surveyed the sky in the mid-IR for about a decade. Our goal is to analyse the mid-IR emission from the well studied massive protostar IRAS20126+4104 and confirm the hypothesis that such emission is periodic, as proposed in previous studies. We take advantage of the NEOWISE, ALLWISE, and Spitzer databases to obtain 24 images of the 3.4 $\mu$m emission from IRAS20126+4104 spanning 19 years, with $\sim$6 months sampling over a decade. With these data we create a light curve for each lobe of the bipolar nebulosity/outflow associated with the protostar. Our results confirm that the IR emission from IRAS20126+4104 varies regularly with a period of $\sim$6.8 yr. The period is the same for both lobes, but their emissions are anticorrelated with a phase difference of $\sim$2.5 yr. The variation is consistent with that found in previous studies for the 6 GHz CH$_3$OH masers and the near-IR emission from the lobes. After discussing four possible ``clocks'' that could determine the observed periodicity, we rule out all but a model involving rotation of the star with a spot obscuring $\sim$20% of the stellar surface. The long rotation period implies that the 12 $M_\odot$ protostar is bloated, with a radius of $\sim$200 $R_\odot$.

The shaping of planetary nebulae on their evolution from asymptotic giant branch circumstellar envelopes to their final, most often axisymmetrical, form is still a process with many unknown details. The key to understanding the whole shaping process is the study of the transition objects called pre-planetary nebulae (pPNe). In this context, modelling tools must be kept to the standard of radio telescope capabilities, so we can make the most of the data they collect. In this work we first present the newest update of the SHAPE and SHAPEMOL modelling tools, adding ten new molecular species to be reproduced together with other general improvements. Later, we put this new update into practice to study M1-92, a pPN with a rich chemistry that can provide valuable information on its origin and shaping. We created a 3D morpho-kinematical model of the nebula in SHAPE that is able to reproduce 23 line profiles from the IRAM 30m telescope and HIFI/HSO and five maps from IRAM NOEMA. The observational dataset is reproduced simultaneously under the same physical conditions, adjusting only the relative abundance of the different species. We obtained a full description of the nebula's physical and chemical properties, and we provide the total estimates for mass (0.79 $M_\odot$), linear momentum (4.10$\times10^{39}$ g cm s$^{-1}$), and kinetic energy (6.48$\times10^{45}$ erg) as well as their detailed distribution across the nebula. We also analysed the isotopic ratios, finding robust discrepancies (values of 10 versus 30) in the $^{12}$C/$^{13}$C ratio across structures depending on their age.

Accurate characterization of filamentary structures in star-forming clouds is essential for understanding star formation. Traditional methods fit observed surface density profiles $\Sigma(r)$ with slope $\gamma$ and width $H$ using the Plummer function, assuming $\beta=\gamma+1$ and $h\approx H$ for the volume density slope and width. These assumptions are inconsistent with the finite nature of filaments. We present a new fitting method that explicitly accounts for finite cylindrical geometry and establishes self-consistent empirical relationships between the parameters of $\Sigma(r)$ and those of the volume density profile $\rho(r)$ with slope $\beta$ and width $h$. The method was validated on model profiles and applied to California filaments. The slope difference $\delta\equiv\beta-\gamma$ falls below unity for shallow ($\beta\lesssim 2$) and compact profiles; $h$ and $H$ can differ by over an order of magnitude for extended filaments with shallow slopes. Accurate parameter recovery requires high resolvedness $R\equiv H/O\gtrsim 10$ (where $O$ is the beam width); at lower resolvedness, slopes are severely overestimated and filaments remain unresolved even when $H\gg O$. The traditional Plummer function yields systematically overestimated slopes. Accurate deconvolution requires a priori knowledge of the true parameters, creating a fundamental circular problem whose only robust solution is obtaining sufficiently high angular resolution. Current far-infrared observations typically lack sufficient resolution, and some previously reported filament properties may require reinterpretation.

We review the role of primordial black holes (PBHs) for illuminating the dark ages of the cosmological evolution and as dark matter (DM) candidates. We elucidate the role of phase transitions for primordial black hole formation in the early Universe and focus our attention on the cosmological QCD phase transition within a recent microscopical model. We explore the impact of physics beyond the Standard Model (SM) on the cosmic equation of state and the probability distribution for the formation of PBHs which serve as candidates for DM and contribute to present-day binary black-hole merger events.

We investigate the impact of a late-time transition in the standardized absolute magnitude $M$ on the best-fit values of cosmological parameters using the Pantheon+ dataset. Extending previous analyses which focused on flat $\Lambda$CDM, we examine this transition within flat $\Lambda$CDM, wCDM, and CPL cosmologies, as well as a model-independent cosmographic expansion, employing both frequentist ($\chi^2$ minimization with \textit{AIC}/\textit{BIC}) and Bayesian (MCMC and Nested Sampling) inference frameworks. We confirm that the data consistently favor a step in absolute magnitude of $\Delta M \simeq 0.19~\mathrm{mag}$ at a characteristic distance of $d_{\mathrm{crit}} \approx 20~\mathrm{Mpc}$. The inclusion of this transition leads to a statistically significant improvement in the quality of fit and has a distinct impact on parameter estimation: it induces a systematic increase in the inferred Hubble constant of approximately $2\%$ across all tested models. In contrast, we find that the dynamical parameters governing the background expansion, including the matter density $\Omega_m$ and the dark energy equation of state ($w_0, w_a$), remain stable and largely unaffected. These results indicate that the $20~\mathrm{Mpc}$ feature acts primarily as a low-redshift calibration shift rather than a modification of the late-time expansion history.

Magnetic fields play a fundamental role in the formation of protostellar winds. In the magneto-centrifugal models, poloidal magnetic fields launch winds from accretion disks, and fast-rotating gas twists the fields into toroidal geometry that collimates and accelerates winds through magnetic hoop stress. However, toroidal fields in protostellar winds remain observationally unresolved. Here we report polarization observations of carbon monoxide emission toward the NGC1333 IRAS 4A protostellar outflow. The inferred magnetic fields are perpendicular to the outflow axis and aligned with the rotational structure of the outflow, indicating toroidal fields with strengths of a few milligauss, sufficient to collimate and accelerate the outflow at several hundred astronomical units from the protostar. A linear correlation is found between the curl of plane-of-the-sky magnetic field and the line-of-sight electric current density. Our analysis provides better constraints on ion-electron drift velocity in protostellar outflows and supports rotating outflows driven by the magneto-centrifugal mechanism.

Context. Be stars are presently viewed as B-type stars surrounded by a disc fueled by the star itself during episodicexcretion events. The origin of these events are poorly this http URL. This article aims to determine whether or not surface equatorial Kelvin waves can be unstable and therefore canplay a role in the triggering of the Be this http URL. We first derive an analytical expression for gravito-inertial modes in the shallow-water framework. Then, weinvestigate numerically the evolution of equatorial Kelvin modes as system parameters vary. The study is extended tothick-layer configurations with a constant density fluid. We then analyze the stability of these modes under differentialrotation and viscous this http URL. We show that equatorial Kelvin waves still exist in a spherical shell of finite thickness, but that their equatorialconfinement is weaker. At low azimuthal wavenumbers, Kelvin waves are in the inertial waves frequency band and thusget specificities of inertial waves like shear layers associated with singularities of the Poincaré equation. These shearlayers are new dissipative structures for Kelvin waves. When a radial (shellular) differential rotation is imposed, we showthat equatorial Kelvin waves can be destabilised provided that differential rotation and viscosity are in an appropriaterange. The non-monotonic behaviour of the growth rate of the instability is traced back to the rise of a critical layerwhere the fluid azimuthal velocity equals the phase speed of the surface this http URL. This study provides new insights into the behavior of equatorial Kelvin waves in astrophysics, particularlyin rapidly rotating stars. The results reinforce the idea that gravito-inertial waves, and more specifically the equatorialKelvin waves, can be unstable and thus be key parts in the mechanisms leading to the Be phenomenon.

We present a new metal enrichment analysis of a unique galaxy group IC 1262 using archival Chandra and GMRT observations, focusing on metal transport via radio jet, sloshing cold fronts, and shock front. This group shows two sloshing cold fronts along the east and north-west direction which is nearly orthogonal to the north - south orientated radio jet. We report discontinuities in the metallicity at the location of previously detected cold fronts, a more prominent one towards the eastern direction. In addition, the gas inside the cold fronts is 45$\pm$8 per cent more enriched than the gas outside the cold front, suggesting the role of sloshing in transporting metals through the IGrM. We also confirm the presence of a previously reported shock front with higher significance and with greater details. Across this shock, we detect a significant metallicity drop from 0.45$\pm$0.05 $Z_{\odot}$ to 0.22$\pm$0.04 $Z_{\odot}$, located at a projected distance of 78$\pm$2 kpc in the southern direction. The shock could potentially account for the region of gas enrichment seen in the abundance map and profile, which could be the result of a non-Maxwellian electron distribution in its vicinity. This should be considered a contributing factor rather than the sole cause of the observed discontinuity in the abundance. Furthermore, our spectral analysis reveals two temperature X-ray gas preferentially aligned with the radio-jet axis, indicating a possible influence of radio AGN activity on the surrounding gas.

In this study, we investigate the dynamical evolution of a massive binary black hole (MBHB) in the Leo I dwarf spheroidal galaxy model and examine how dark matter along with stellar matter's gravitational interactions influence its long-term behavior. Using high-resolution direct N-body simulations, we follow the orbital evolution of the binary within a realistic model of the Leo I stellar and dark matter distribution. We found that the binary separation decreases from an initial 300-parsec orbit to roughly 1 parsec over a period of about 2 Gyr, primarily driven by dynamical friction and stellar hardening. The orbital evolution then stalls at this scale, illustrating the well-known final parsec problem. During this phase, the binary also develops increasing orbital eccentricity and produces a modest redistribution of the inner mass profiles in some cases. We then further estimate the final stage of the system's evolution using gravitational-wave emission models and find that the binary is unlikely to merge within a Hubble time. The prolonged dynamical friction phase appears to be related to the low stellar and dark matter densities in Leo I. These results suggest that massive binary black holes in dwarf spheroidal galaxies such as Leo I will not contribute to the gravitational-waves detectable from LISA even if dark matter is considered.

We present PHLEGETHON, a fully compressible, Eulerian magnetohydrodynamic (MHD) code designed for multidimensional simulations in stellar astrophysics. The code uses a time-explicit, second-order, finite-volume method optimized to model a wide range of dynamical processes in stars, from very low-Mach-number turbulent convection in the cores of massive stars to supersonic flows in subsurface convection zones. PHLEGETHON employs low-dissipation Riemann solvers and a well-balanced method to accurately capture slow flows arising from strongly stratified media. The induction equation is solved using a staggered constrained-transport method to ensure divergence-free evolution of the magnetic field. The MHD equations are coupled to arbitrary nuclear reaction networks solved in a time-implicit approach, together with super-time-stepping for efficient treatment of thermal diffusion. Equations of state appropriate for stellar plasmas are available, accounting for partial ionization, electron degeneracy, and electron-positron pair production. The code is implemented in a compact and user-friendly manner, and it scales to tens of thousands of CPU cores using MPI-based domain decomposition. We perform several verification tests to demonstrate the accuracy and versatility of the code, and present simulations of magnetoconvection in a core-collapse supernova progenitor star. The rich variety of physical effects and numerical methods implemented in PHLEGETHON enables the code to model diverse multidimensional processes that play a crucial role in stellar-interior dynamics, such as reactive convection, convective boundary mixing, internal-wave excitation, and magnetic-field amplification mechanisms. Within a single framework, these phenomena can be investigated across a wide range of stellar evolutionary stages, from main-sequence stars to supernova progenitors. PHLEGETHON is publicly accessible online.

Core-collapse supernovae (CCSNe) in luminous infrared galaxies (LIRGs) can have extreme line-of-sight host galaxy dust extinctions, which leads to a large fraction of the events remaining undetected by optical and infrared surveys. This population of undetected CCSNe is important to constrain in order to determine the cosmic CCSN rates. Our aim is to confirm and refine our estimates for the undetectable fraction of CCSNe in LIRGs in the local Universe. Our study is based on the near-infrared K-band multi-epoch SUNBIRD survey monitoring dataset of a sample of nine LIRGs using the Gemini-South telescope with the multi-conjugate GSAOI/GeMS laser guide star adaptive optics system. We determined the limiting magnitudes for CCSN detection for each epoch in our dataset with artificial supernova injection and image subtraction methods. Subsequently, we used a Monte Carlo method to determine the combined effects of limiting magnitudes, survey cadence, CCSN subtype distribution, and their light curve evolution diversity. The intrinsic CCSN rates of the sample galaxies were estimated based on detailed modelling of their spectral energy distribution. Finally, we combined the resulting CCSN detection probabilities with the intrinsic CCSN rates for the dataset, and compared that against the real CCSN detections over the survey period. Based on our GSAOI/GeMS dataset, assuming optical or near-infrared example surveys with capabilities to detect CCSNe in local LIRGs with host extinctions of $A_V =$ 3 or 16 mag, respectively, the resulting total undetectable fractions are $86.0^{+4.7}_{-5.9}$ % and $53.6^{+15.6}_{-19.6}$ %. When folding in the results from our previous near-infrared adaptive optics assisted LIRG monitoring dataset, the corresponding total undetectable fractions are $88.3^{+2.6}_{-3.2}$ % and $61.4^{+8.5}_{-10.6}$ %, respectively.

Light curves from binary systems containing white dwarfs with neutron star or stellar-mass black hole companions (WD+NS and WD+BH) with edge-on orbital planes potentially show self-lensing/eclipsing signals. Here, we evaluate the properties and detectability of these signals in the NASA's Transiting Exoplanet Survey Satellite (TESS), and the Nancy Grace Roman Space Telescope (Roman) observations. WD+NS systems with orbital periods $T\lesssim25~$days mostly have considerable finite-source sizes with the normalized source radii $\rho_{\star}\gtrsim1$. WD+BH systems with $T\gtrsim3$ days have $\rho_{\star}\lesssim1$, and $\rho_{\star}\sim0.01$ for BHs with a few tens solar-mass. Our analytical calculations show the probabilities of occurring self-lensing signals in WD+NS and WD+BH systems are $\sim10^{-3},~10^{-2}$, and maximize for systems with low-mass WDs revolving massive NSs/BHs. We simulate their light curves and generate synthetic data for them by applying the observing protocols of these two satellites. We assume self-lensing signals are detectable if (i) $1\leq T\leq T_{\rm{obs}}$ (where $T_{\rm{obs}}=62~\rm{and}~27.4$ days are the Roman and TESS continuous observing windows), (ii) $\rm{SNR}\ge3,~6$, their signals are (iii) deeper than twice the photometric error, and (iv) covered by at least one datum. Systems with detectable self-lensing signals in the TESS and Roman observations on average have small inclination angles $i\lesssim0.2^{\circ}$, with the orbital periods $\sim6,~19~$days, and their signals last $\sim[6,~30]~\rm{minutes}$. The TESS and Roman efficiencies for detecting these signals are $\sim2-6\times10^{-4}$ and $\sim2-12\times10^{-10}$. Although detecting these self-lensing signals by Roman is impossible, the TESS telescope potentially manifests at least one self-lensing signal due to these binary systems, if $8\%,~\rm{and}~3\%$ of WDs have NS and BH companions.

Within the volume-limited subsample at $z<0.06$ of the Zwicky Transient Facility (ZTF) DR2 sample, we confirm a statistically significant excess of Type Ia supernovae (SNe Ia) at $z \simeq 0.02$-$0.04$, previously reported but not explained by survey selection effects. Forward simulations assuming a uniform volumetric SN Ia rate and realistic ZTF detection efficiencies fail to reproduce the feature at the $5$-$7\sigma$ level. We also detect an excess in the rates compared to our survey simulations at $z \simeq 0.08$ and $0.14$, albeit at smaller significance. To investigate the origin of these inhomogeneities, we compare the observed SN distribution to constrained reconstructions of the local matter density field from the Manticore project, based on Bayesian forward modelling of the 2M++ galaxy catalogue. While SN overdensities are spatially associated with prominent nearby structures such as the Perseus, Coma, and Hercules superclusters, the amplitude of the SN excesses significantly exceeds that expected from matter overdensities alone. By reconstructing a redshift-dependent volumetric SN Ia rate, we find that local enhancements can reach factors of two to five within specific clusters, while the sample-averaged rate remains consistent with previous low-redshift measurements. These results indicate that the SN Ia rate is not a linear tracer of the underlying matter density and suggest a strong environmental dependence in dense structures. We discuss possible physical origins and highlight the implications for low-redshift SN cosmology, including correlated peculiar velocities and additional covariance beyond standard linear corrections.

Here we present a survey aimed at detecting hydroacoustic signals from fireballs using the six hydrophone stations operated as part of the Comprehensive Test Ban Treaty Organisation (CTBTO) International Monitoring System. We identified 30 fireballs where propagation paths to stations exist. These included high energy fireballs (E $\geq$ 5 kT), those which occurred over favorable locations for coupling into the deep ocean as well as a selection of bolides close to CTBTO hydrophone stations. The largest of these impactors were $>$ 5 meters in diameter. From theoretical and empirical considerations we show that direct hydroacoustic shock transmission is the most likely source mechanism, though large meteorites impacting the ocean surface from a fireball might be detectable in extreme cases. We find one possible instance of a fireball occurring on Sep 2, 2003 off the coast of Alaska, where a linked hydroacoustic signal with the expected timing and backazimuth is detected. However, given the size of our survey and the random background rate of signals, this detection is statistically weak. We conclude that hydroacoustic detection in the SOFAR channel of fireballs is very rare. Using our chosen set of signal processing parameters, assuming direct path H-phase signals, adopting a signal celerity range of 1.42-1.55 km/s we find no unambigous detections in 53 station-fireball pairs. Based on SOFAR-equivalent yields derived assuming the minimum detectable amplitude signal family association is representative of the noise background in our survey we estimate a conditional upper limit for fireball coupling efficiency of order 10$^{-10}$. A single well recorded airplane impact provides an empirical estimate for the energy coupling of surface ocean impacts to the SOFAR channel of 10$^{-4}$ for high velocity surface impacts.

Generally, large solar flares accelerate electrons to high energies more efficiently than microflares. However, some microflares, known as hard microflares (HMFs), also produce high-energy electrons, as indicated by their flat hard X-ray (HXR) spectra. These events are typically associated with footpoints located in or at the edge of sunspots. The mechanisms behind this efficient acceleration, and their connection to solar energetic electrons (SEEs), remain unclear. We compare, for the first time, HXR spectra of HMFs with in-situ electron spectra of associated SEEs using Solar Orbiter STIX and EPD observations. This provides insight into acceleration processes and the transport of high-energy electrons into interplanetary space. We identify eight HMFs observed jointly by Solar Orbiter and Earth-based instruments that are associated with SEEs, confirmed through timing and magnetic connectivity analysis. Each event is studied using HXR spectroscopy, SEE velocity-dispersion analysis, and in-situ electron spectral analysis. Seven of eight events show consistent timing between flare HXR emission and inferred electron injection, as well as good agreement with magnetic connectivity estimates. The known correlation between HXR photon and in-situ electron spectral indices extends to HMFs, which occupy the hard end of the distribution, even compared to larger flares. We conclude that HMFs produce prompt SEEs with hard spectra, demonstrating efficient electron acceleration without requiring large flare energy release. Their magnetic configuration, involving open field lines from the sunspot, suggests they may be an important contributor to filling the heliosphere with energetic particles.

The PLAnetary Transits and Oscillations of stars (PLATO) mission is expected to launch in January 2027. A total of 8\% of its data rate will be dedicated to complementary science targets selected from approved Guest Observer proposals. We seek to provide an open-source catalogue of variable stars in PLATO's first long-term observing field, LOPS2. We want to use existing observations from the Transiting Exoplanet Survey Satellite (TESS), which has observed many stars in LOPS2. We classified 38 million calibrated aperture light curves from the TESS-Gaia Light Curve pipeline (TGLC, $G\lesssim17$) for 6 million unique sources in LOPS2 with two machine learning frameworks -- a deep neural network and a feature-based gradient-boosted decision-tree ensemble. We combined their predictions to create this first version of the LOPS2 variability catalogue, performed manual vetting of a sub-sample classified light curves, and a statistical analysis of the results to validate our methodology and to assess the variability properties and parameters of the stars in the catalogue. Our classification resulted in the identification of approximately 72% of the light curves having dominant instrument- or pipeline-induced signal, with the remaining 28% representing 3.6 million individual candidate variable stars, including pulsating, rotating, and eclipsing stars. Candidate pulsators exhibit varied behaviour in terms of their frequencies, amplitudes, rotation, and fundamental parameters. To ensure purity of the samples, filtering on colour, luminosity, the dominant frequency and its amplitude, and presence of close neighbours is helpful. We provide the first version of our PLATO LOPS2 variability catalogue to the community for further study and scrutiny. It is to date one of the largest catalogues of variable stars from an automated classification pipeline.

Persistent radio sources (PRSs) are (sub-)parsec-scale compact non-thermal continuum sources associated with some repeating fast radio bursts (FRBs). Their nature is debated, but their properties provide insights into the FRB environment and progenitors. We measure the spectrum of the recently confirmed PRS associated with FRB 20190417A. Spectral features such as the self-absorption and cooling break can be used to constrain the age and size of PRSs and test theoretical models. We present observations made with the 1.26 GHz upgraded Giant Metrewave Radio Telescope (uGMRT) and observations from the 6 GHz Karl Jansky Very Large Array (VLA). With complementary archival data and the LOw Frequency ARray Two Meter Sky Survey (LoTSS), we characterise the spectrum of the PRS between 144 MHz and 6 GHz. The spectrum follows a power-law behaviour at gigahertz frequencies. The source is not detected at 144 MHz down to a $2\sigma=170 \; {\rm \mu Jy}$ sensitivity. We modelled the spectrum with a broken power law, obtaining a spectral index $\alpha = 0.20 \pm 0.05$ between 1-6 GHz. We placed a lower limit on the turn-over frequency of $> 370$ MHz ($95\%$ confidence). The flat spectrum and low-frequency turn-over of the target are consistent with the spectral properties predicted for magneto-ionic nebulae, inflated behind the supernova ejecta by a flaring young magnetar. Considering the multi-zone magnetar wind nebula scenario, we estimate an age of $t< 250$ yr and a radius of $R< 0.4$ pc for the target, which would thus be slightly older than the PRSs associated with FRB 20121102A and FRB 20190520B.

Context. Studying the kinematic and dynamic evolution of fast eruptive events from the middle to high solar corona is a primary objective of the Metis coronagraph on Solar Orbiter. During perihelion, Metis acquires visible light images at a 20s cadence, reaching a spatial resolution of around 2000 km at 0.28 au. This enables capturing coronal mass ejections (CMEs) and transient structures with unprecedented spatial and temporal resolution. Aims. On October 8-9, 2022, an extensive CME was observed by Metis at 0.3 au (resolution: 4.4 $10^{3}$ km/pixel). We aim to exploit this high resolution to resolve multiple substructures within the CME front, revealing plasma elements with distinct trajectories and speeds to provide a detailed kinematic characterization of the eruption. Methods. A normalization-based running difference algorithm was applied to enhance the complex morphology. Height-time diagrams were used to estimate propagation speeds and frequency variations. A 3D flux rope reconstruction, combined with multi-spacecraft coronagraphs and disk imagers, enabled tracking the CME from its initiation in the lower corona to approximately 5 solar radii. Joint observations with Solar Orbiter EUI-FSI provided insights into the eruption's onset, while Metis captured its development into the middle corona. Results. Metis observations resolve the CME's fine structure and internal plasma motions. The detection of circular, fast-propagating wavefronts (500 km/s, 3 minute period) at the western flank suggests wave excitation and magnetic reconfiguration processes. Multiple interpretations are proposed for these coronal wave trains, including quasi periodic propagating fast modes, offering new insights into wave generation and energy transport in the solar corona.

Gaia has the potential to deliver several tens of new dormant black holes (BHs) with low-mass stellar companions (hereafter, Gaia BHs) in the upcoming fourth data release. Three Gaia BHs are already known, but their formation pathways remain uncertain. Here, we perform a large parametric study to explore the formation of Gaia BHs from isolated binary systems with the population-synthesis code SEVN and compare our models with the properties of the three already reported Gaia BHs. Specifically, we explore the impact of accretion efficiency, mass transfer stability, natal kicks, angular momentum transport, and core-collapse supernova prescriptions. We find that models in which stable mass transfer is highly non-conservative and angular momentum is lost as a wind from the donor surface (Jeans mode) maximize the probability of forming dormant systems that match the properties of the observed Gaia BHs in terms of both orbital period and eccentricity, because such assumptions prevent the initial orbit from shrinking too much when the BH progenitor fills its Roche lobe. If we allow for common-envelope evolution, we find that models with common-envelope ejection efficiency $\alpha{} < 1$ predict dormant systems with orbital periods that are too short compared to the observed Gaia BHs. The eccentricity of the observed Gaia BHs, when combined with information about orbital period and BH mass, favors relatively large natal kicks, similar to those inferred from Galactic neutron stars. Finally, models in which the natal kicks are low - e.g. because they are modulated by fallback - result in the formation of a large population of dormant BHs with long orbital periods ($P_{\rm orb}>10^4$ days) and low eccentricity, which will be tested soon by the fourth Gaia data release.

We analyze JWST spectroscopy of the northwest filament of NGC7023, where the relatively soft radiation field results in a photodissociation region with an extended atomic hydrogen region, and strongly pronounced variations of the carbonaceous emission band profiles. We focus on the 16.4 and 17.4 um bands and their relation to the main bands at 3.3, 3.4, 5.2, 5.7, 6.2, 7.7, 8.6, 11.3, and 12.7 um, and aim to identify which bands and sub-features originate from co-spatial emission carriers. We apply a PAHFIT spectral decomposition to measure the emission bands and their individual sub-components, and produce maps that spatially resolve the main dissociation front (DF1). Nearly all emission maps peak at DF1, while the relative intensity in the atomic hydrogen region (ATM) varies strongly. We classify the features into spatial distribution types based on the intensity ratio in ATM relative to DF1. Most bands are of type I (low ATM/DF1; 3.3, 3.4, 5.2, 5.7, 11.3 um) or II (medium ATM/DF1; 16.2, 7.7, 8.6, 12.7, 16.4 um), while only few are of type III (high ATM/DF1; 11.0, 17.4 um). A breakdown of the 5.7, 7.7, 11.3 and 12.7 um bands into blue and red sub-components reveals that contributions on the blue side are of type III, while those on the red side are of type I or II. These strongly differing spatial distributions reveal that at least two different populations contribute to the 16-18 um range, and that these populations are also connected to the profiles of the 5.7, 7.7, 11.3, and 12.7 um bands. The maps further indicate a continued evolution of these profiles toward the central cavity of NGC7023, where fullerene emission (C60) was previously detected. We speculate that the population of emission carriers could be in an intermediate photochemical evolution stage that precedes fullerene formation.

While the connection between massive stars and supernova explosions is well established observationally, the link between massive stars and black hole formation remains elusive. Some massive stars may collapse directly to black holes without a successful supernova, and may therefore appear as disappearing stars. We investigate the expected photometric properties of such black hole progenitors by combining detailed single and binary stellar evolution models with physically motivated prescriptions linking pre-collapse core structure to explosion or direct collapse outcome, together with stellar atmosphere calculations, producing synthetic photometry across standard ultraviolet to infrared filters. Weighting by an initial mass function and empirical binary distributions, we predict both the observable distribution of progenitor brightness and colour and the rate of direct-collapse events, which we estimate to be about 0.4 per century for a galaxy forming stars at 1 Msun/yr. We find that black hole progenitors are predominantly hot and blue at the pre-collapse stage, with many in Wolf-Rayet phases and luminous in the ultraviolet, while only a minority are red supergiants. Consequently, searches that focus primarily on red supergiants are likely to miss a substantial fraction of direct-collapse events. Monitoring campaigns that include ultraviolet-sensitive observations of nearby star-forming galaxies therefore provide a promising route to detecting disappearing massive stars, offering a direct observational probe of black hole formation. Our results provide predictions to interpret such surveys and constrain the channels that lead to black hole formation.

The actinides, including thorium (Th), are the heaviest observable elements synthesized in the universe, holding clues to the extremes of the astrophysical and nuclear conditions of $r$-process sites. We present Th abundances based on high-resolution spectroscopy for 47 metal-poor stars, the largest homogeneously analyzed sample to date. The chemical evolution of Th exhibits a decrease in dispersion in [Th/H] and [Th/Fe] from $\sim$0.6 dex at the lowest metallicities to $\sim$0.2 dex at higher metallicities. We also find that Th and the lanthanides Eu and Dy are co-produced remarkably well, with average [Th/Eu]$\sim0.0$ across $-3.0 \lesssim$ [Fe/H] $\lesssim -1.5$, as well as across stars with $0.0\lesssim$ [Eu/Fe] $\lesssim2.5$. Even so, the absolute range of $\log\epsilon$(Th/Eu) is 1.02 dex, with an observed standard deviation of $\pm0.20$ dex and an intrinsic standard deviation of $\pm0.11$ dex at the lowest metallicities. We infer that $68\%$ of $r$-process events have $\log\epsilon$(Th/Eu) yields that only vary within a factor of $\pm1.3$ or $\pm30\%$, while $5\%$ of $r$-process events have $\log\epsilon$(Th/Eu) yields that vary by factors $>3.3$ approaching $\sim$10. This serves as a strong constraint for the nuclear and astrophysical models of $r$-process sites, and suggests that achieving an $r$-process site that is both prompt and produces a robust $\log\epsilon$(Th/Eu) ratio is a challenge for current models.

VLBI measurements of the sizes of compact extragalactic radio sources, jetted active galactic nuclei, provide data for probing the angular size--redshift relation, offering a complementary test to other distance--redshift methods. We analyse a significantly expanded dataset to reassess the angular size--redshift relation and its potential for constraining cosmological model parameters, focusing on the matter density parameter $\Omega_{\mathrm{m}}$ in a flat $\Lambda$ Cold Dark Matter Universe. This is the first major update of the compact-source angular size test in the past quarter of a century, using a dataset an order of magnitude larger than in previous studies. MCMC analysis on real data and on multiple mock catalogues to evaluate parameter constraints in the presence of observational scatter. In addition, we conducted a test with 100 randomized catalogues created by shuffling redshifts while preserving other observables. We also explored how astrophysical parameters depend on fixed cosmological models with different $\Omega_{\mathrm{m}}$ values. The randomization test showed that the posterior distributions from randomized data do not overlap with those from real observations, confirming that the measured angular size--redshift relation is physically meaningful. The astrophysical model parameter that describes the redshift dependence of the source angular size exhibits degeneracy with $\Omega_{\mathrm{m}}$. Simulated mock catalogues indicate that the method is able to constrain $\Omega_{\mathrm{m}}$ if the data scatter is below $\sim20\%$. Scaling estimates suggest that high-quality data of samples of several thousands to $\sim 100\,000$ sources, a standardisation calibration approach, and/or refining sample selection criteria are needed to fully exploit the potential of the angular size--redshift test with this type of objects (abridged).

We investigate how strongly late-time inferences about DE dynamics depend on the functional prior used to represent the expansion history. Using identical late-time combinations of CC, DESI BAO measurements, the Pantheon+ SN1a sample, and the H0DN prior, we compare a node-based reconstruction of the reduced Hubble function $E(z)$ with a representative family of smooth low-dimensional DE EoS parametrizations, including CPL. Over the redshift range constrained by the data, both approaches yield consistent $H(z)$, and, in the absence of H0DN, compatible values of $H_0$. However, a clear method dependence emerges at intermediate redshift ($z\sim1.7$): the reconstruction favors stronger deceleration, $q_{\rm Rec}(1.7)\simeq0.56-0.61$, whereas the smooth parametrizations cluster at $q(1.7)\simeq0.32-0.40$, implying a persistent $\sim2-3\sigma$ discrepancy across dataset combinations and parametrizations. For the EoS-based parametrizations, whose effective DE densities remain positive by construction, the preferred $w_{\rm DE}(1.7)<-1$ values correspond to NECB-violating (phantom-like) behaviour, but this is a less robust discriminator as $w_{\rm DE}$ becomes ill-conditioned as $\rho_{\rm DE}\to0$. In the effective-fluid mapping, the reconstruction accommodates the same late-time kinematical preference through a rapid descent of $\rho_{\rm DE}(z)$ toward very small values and a sign change, whereas the EoS-based parametrizations absorb it through smoother, and in several cases NECB-violating, evolution over $z\sim1-2$. Although the reconstruction improves the best-fit likelihood, especially with H0DN, Bayesian evidence continues to favor the simpler parametric descriptions. Our results isolate $z\sim1.5-2$ as the key window in which EoS-based DE parametrizations can compress localized kinematic structure and associated features of DE that are still permitted by current late-time data.

Supersonic winds from massive stars carry great amounts of kinetic power and modify the surrounding interstellar medium. Through this interaction a stellar bubble is formed. Theoretical studies and recent observations suggest that the winds of massive stars could be sources of Galactic cosmic rays. The first detection of synchrotron emission from the bubble of a single star was reported, indicating the presence of relativistic electrons. Studying the non-thermal emission from a single massive star can help to better understand the acceleration of particles taking place in massive star clusters. WR 102 is the perfect case of study. In this work, we present the first high-energy model for the bubble of WR 102: G2.4+1.4. We aim at fitting the radio data and predicting gamma-ray emission. We assume that both electrons and protons are accelerated at the wind shock. We applied a classical model for the stellar bubble and adopted a one-zone model for estimating the radiation produced by the relativistic particles near the acceleration region. Additionally, we computed the expected emission from the protons that diffuse to the outer regions of the bubble. Also, we estimated the leptonic and hadronic contributions expected from cosmic rays. We fitted the observations considering that 3% of the wind kinetic power goes into relativistic electrons, and a magnetic field of 250 $\mu$G. The dominant component at high energies is produced by locally accelerated protons reaching the shell. Protons might reach PeV energies in the wind bubble, but the predicted gamma-ray flux is too low to be detectable.

Scalar-induced gravitational waves (SIGWs) have recently attracted considerable interest, both as a possible explanation for the nanohertz signal reported by the Pulsar Timing Array (PTA) collaboration and for their connection with primordial black hole (PBH) physics. In addition to SIGWs, scalar-tensor-induced gravitational waves (STGWs) have emerged as a promising cosmological source of the stochastic gravitational wave background (SGWB). In this paper, we compute the STGWs generated during a generic matter-dominated (MD) era, as well as during an early matter-dominated (eMD) epoch followed by a sudden transition to the standard radiation-dominated (RD) stage, working in the Poisson gauge. We find that, in a purely MD age, the corresponding energy density rapidly dilutes, whereas in the presence of an eMD phase it remains non-vanishing due to the short duration of the eMD period. We then investigate whether the STGW signal could provide a dominant contribution to the $\texttt{NANOGrav 15-year}$ dataset and we forecast the prospects for its detection with future observations by the Square Kilometre Array (SKA). In particular, we consider STGWs generated during both eMD and RD eras, including their linear-order contributions. Our results show that the GWs induced by scalar-tensor mixing constitute a viable target for future, more sensitive detections of the SGWB.

Although Uranus and Neptune are commonly classified as ice giants, their exact compositions remain poorly constrained. Recent studies of outer Solar System bodies challenge the traditional view that these planets are primarily ice-dominated, suggesting that refractory material plays a more significant role. Determining the proportions of ice and rock within Uranus and Neptune is essential for understanding their formation and the evolutionary history of the Solar System. In this work we computed interior structure models for both planets and explored, within a Bayesian framework, the range of compositions that satisfy the available observational constraints. We quantified the resulting ice and rock fractions and analyzed their impact on the inferred internal structure. Our results suggest that the envelopes of both Uranus and Neptune are systematically enriched in refractory material, with median rock fractions of approximately 60% within the heavy-element component, similar to Pluto, Kuiper belt objects, and comets. In contrast, the deep interiors of the two planets exhibit distinct compositions: Neptune is best fit by relatively rock-rich mantles (median rock fraction of ~ 55%), whereas Uranus is inferred to have more ice-rich mantles (median rock fraction of ~ 41%), consistent with a more strongly stratified structure. These results point to compositional differences between Uranus and Neptune that may reflect divergent formation and evolutionary pathways.

The issue and proof of Gurzadyan theorem are presented concisely, avoiding tedious and unnecessary calculations that would mask what is essential. The goal is to provide a good mathematical and physical understanding of the theorem, making you want to learn more about its use in cosmology.

This paper investigates a phased array ground station capable of tracking multiple sources, multi-beamforming, electronic steering, easy scaling, and low cost. The project will develop a 20-pair dual-polarized yagi-UHF/VHF phased array with a pseudo-random layout, comparing parameters of random and uniform distributions. We will present several analyses: general analysis for side lobes across both elevation and azimuth, analysis of scaling with number of elements ("element sweep"), electronic beam steering analysis, mechanical beam steering analysis, electro-mechanical beam steering analysis, array density analysis, and reception/transmission spectra analysis.

During the voyages that led him to discover the new continent bearing his name, Amerigo Vespucci made interesting astronomical observations of the southern sky. In the past, his data have been interpreted with criteria that do not follow Vespucci's indications, resulting in identifications that are not credible or even leading to the assertion that the data themselves are incomprehensible. However, it is possible to construct a coherent picture of all the information, arriving at an identification that is in some cases very probable, in other cases almost certain, of the stars described by Vespucci. Analysis of documents shows that he made good-quality measurements, but his incomplete knowledge of ancient texts prevented him from distinguishing the new stars from the already known ones, giving rise to a period of confusion in 16th century celestial cartography.

We study the geodesic motion and epicyclic oscillations of massive test particles around a static, spherically symmetric black hole (BH) solution of the Einstein--Skyrme (ES) theory in Anti-de Sitter (AdS) spacetime. The lapse function of this BH depends on the Skyrme coupling $\eta$, a charge-like parameter $Q$ inherited from the Skyrme term, and the cosmological constant $\Lambda<0$. We first map out the horizon structure and identify three regimes-non-extremal BH (NEBH), extremal BH (EBH), and naked BH (NBH)-showing that the NEBH $\to$ EBH $\to$ NBH transition is governed by $Q$ rather than $\eta$, which enters $f(r)$ only as a constant shift. We then derive the effective potential (EP), locate the innermost stable circular orbit (ISCO), and compute the radiative efficiency, finding that $\mathcal{E}_{\rm ISCO}>1$ in AdS renders the standard Novikov-Thorne formula negative. The corrected radial epicyclic frequency $\Omega_r$ reveals a distinctive AdS signature: $\nu_r$ grows at large $r$ and overtakes the orbital frequency $\nu_\phi$, causing the periastron precession frequency $\nu_p = \nu_\varphi - \nu_r$ to change sign-a feature absent in asymptotically flat geometries. Adopting the relativistic precession (RP) model for quasi-periodic oscillations (QPOs), we perform a Markov chain Monte Carlo (MCMC) analysis using twin-peak QPO data from XTE~J1550-564, GRO~J1655-40, Sgr~A$^*$, and M82~X-1. The posteriors converge to $Q\approx 0.6$ across all sources, with orbital radii near $r\approx 4.2\,M$ and masses consistent with independent estimates, demonstrating that the ES-AdS BH accommodates the observed frequency pairs within physically motivated parameter ranges.

A new radiation solver, RAPRAL (RAdiation Prediction based on RAy tracing and Line-by-line) implemented in C++, is developed for simulating high-temperature thermochemical nonequilibrium radiative processes. RAPRAL integrates detailed line-by-line spectral modeling with a ray-tracing solution of the radiative transfer equation, enabling accurate resolution of both spectral features and spatial radiation transport. The adopted methods and their implementation are described in detail. To assess the overall capability and accuracy of RAPRAL, we first focus on the computation of atomic and molecular bulk spectral coefficients. Through comparison with the established code in the literature, RAPRAL demonstrates its ability to accurately capture key spectral features across a wide range of conditions. Moreover, RAPRAL is applied to predict afterbody radiative heating in the Fire II flight experiment, based on a two-temperature, 11-species air flowfield. The results demonstrate that the present approach provides reliable predictions of radiative heat flux and effectively captures the dominant radiation mechanisms. Overall, the presented results demonstrate that RAPRAL is a robust tool for simulating radiative processes in hypersonic air flows, and future versions will extend its capabilities to include species relevant to planetary atmospheres.

Next-generation (XG) gravitational-wave detectors, such as Cosmic Explorer (CE) and the Einstein Telescope (ET), will observe compact binary coalescences at unprecedented rates and signal-to-noise ratios (SNRs). Accurate sky localization of these sources is crucial for several aspects of the science case of CE and ET. The localization of most binary black hole (BBH) signals, which will spend at most a few minutes within the XG detector's effective sensitivity band, will continue to rely primarily on timing triangulation across a network of detectors. A key design choice for triangulation is the baseline between instruments. We investigate how the baseline affects the localization capabilities of a two-detector CE network, analyzing both fixed-parameter injections and a realistic BBH population consistent with the latest GWTC-4 results. For detector-frame total masses up to $\sim\!100\,{\rm M}_\odot$, we find that baselines corresponding to light travel times of $8-11$ ms ($\sim\!2300-3300$ km) offer a reasonable compromise, producing predominantly unimodal or bimodal sky localizations suitable for electromagnetic follow-up and statistical host galaxy identification and galaxy cross-correlation studies. Shorter baselines significantly degrade localization, particularly for high SNR events. Crucially, we find that adding a third detector to the network eliminates localization multimodality for a substantial fraction of sources. A network with two CEs and LIGO-India provides unimodal posteriors for a good fraction of events, whereas two CEs plus ET would provide unimodal posteriors for essentially all of them. These considerations should be useful to inform the development of the XG detector network.

We present GreyRing, a new model for the post-merger signal in black-hole binary coalescences based on the greybody factor of the remnant. The model accurately reproduces the full frequency-domain ringdown signal of a large set of comparable-mass, aligned-spin numerical relativity waveforms, achieving mismatches of order ${\cal O}(10^{-6})$ for the dominant $(\ell,m)=(2,2)$ mode, and typically outperforming state-of-the-art time-domain models. Building on this model, we introduce a novel consistency test of strong gravity based on the greybody factor: the remnant mass and spin inferred from GreyRing can be compared with those obtained through standard black hole spectroscopy. This agnostic test relies exclusively on the post-merger signal and does not require the inclusion of overtones or the choice of very early ringdown starting times, combining the advantages of inspiral-merger-ringdown consistency tests and traditional black hole spectroscopy. We apply the test to GW250114 and find that the remnant mass and spin inferred from GreyRing are consistent with those measured from the full signal. Remarkably, the inferred parameters can be measured with a precision comparable to, or slightly better than, that achieved with standard black-hole spectroscopy. Our greybody-factor waveform model allows for new precision tests of strong gravity using the ringdown signal.

We introduce pyEFPEHM, a post-Newtonian (PN) inspiral waveform model for eccentric and spin-precessing compact binaries that includes higher-order modes and matter effects. Accurate and efficient waveform models capturing these effects are essential for probing compact-binary formation channels and exploiting current and future gravitational-wave (GW) observations. pyEFPEHM extends pyEFPE, significantly improving its physical content and accuracy. In particular, we show that above 2.5PN order the quasi-circular contributions to the orbital phasing dominate at each PN order, and incorporate all available higher-order quasi-circular PN corrections to the phasing, including adiabatic tidal effects. We generalize the multiple-scale analysis solution of the spin-precession equations, extending it to higher PN orders and including all available quasi-circular corrections. Finally, we add eccentric corrections up to 1PN order in the waveform amplitudes, including the GW multipoles $(l,|m|)=(2,2),(2,1),(2,0),(3,3),(3,2),(3,1),(3,0),(4,4),(4,2),(4,0)$. We validate pyEFPEHM against analytical waveform models and numerical relativity simulations, showing that it provides a robust and computationally efficient description of the inspiral, with good agreement across a broad region of parameter space and up to close to merger. The accuracy degrades in the late inspiral for systems with very unequal masses ($m_2/m_1 \lesssim 0.1$), significant spins aligned with the orbital angular momentum ($|\chi_\mathrm{eff}| \gtrsim 0.5$), and high eccentricities ($e \gtrsim 0.6$), where the PN expansion is expected to break down. pyEFPEHM represents a significant step toward physically complete and efficient waveform modeling of eccentric and precessing binaries, providing a foundation for future extensions including higher-order corrections, calibration to numerical relativity, and merger ringdown modeling.

We report the properties of electron distributions and turbulence during a Coronal Mass Ejection (CME) in April 2023 observed by Magnetospheric Multiscale (MMS). The CME exhibits a clear sheath and magnetic cloud (MC), and within the MC, the solar wind becomes sub-Alfvénic for two hours. We investigate plasma and turbulence properties of the sub-Alfvénic CME wind and compare them with those in the super-Alfvénic solar wind in the MC and CME sheath. Electrons within the sub-Alfvénic MC show significantly higher temperatures than those in the CME sheath and the super-Alfvénic MC, with their one-dimensional distributions revealing super-thermal tail and a depletion in electron populations between 15-50 eV. Within the CME sheath, isolated regions of electron heating are observed, where parallel energy flux is enhanced up to ~1 keV. Magnetic field fluctuations within the sub-Alfvénic MC interval exhibit negligible cross helicity and steeper-than-Kolmogorov scaling in the inertial range, with no clear spectral break. These fluctuations also show reduced intermittency at ion and sub-ion scales, emerging intermittency at electron scales, and weak magnetic compressibility. Together, these observations point to the presence of weak magnetohydrodynamic (MHD) turbulence within the sub-Alfvénic MC, resembling conditions commonly observed in planetary magnetospheres such as Jupiter's.

It has been assumed that hydrogen is negligibly incorporated into core-forming metals below $\sim$3 GPa, and therefore the presence of hydrogen in iron cores of small terrestrial bodies including the moon has not been considered. Here we performed high-pressure melting experiments on the Fe-H system under H$_2$-saturated conditions, combined with synchrotron X-ray diffraction (XRD) measurements. Results demonstrate substantial depression of the Fe-H melting curve compared to that for Fe at 1.0-3.3 GPa, indicating that hydrogen is incorporated into liquid iron even at low pressures less than 1 GPa and the solubility is enhanced with increasing pressure. Based on the density of liquid Fe-H derived from diffuse scattering signal in XRD data, we found that the solubility of hydrogen in liquid iron is about 0.9 wt% at 3.6 GPa and likely enhanced to 1.2 wt% at 5 GPa corresponding to lunar core conditions. The 1.2 wt% H causes 9 % density reduction, which might fully explain the observed density deficit of the lunar core with respect to iron, depending on the density estimate from seismological data.

We study graviton production from an oscillating inflaton condensate during reheating by systematically comparing Boltzmann and Bogoliubov descriptions for inflaton potentials of the form $V(\phi)\propto\phi^n$ around the minimum. The Bogoliubov framework provides a unified description of graviton production, capturing both perturbative and non-perturbative effects across short and long wavelengths, whereas the Boltzmann approach is restricted to perturbative production at short wavelengths. For the quadratic case ($n=2$), we find that the two approaches yield identical graviton spectra at short wavelengths, indicating that the Boltzmann treatments fully captures perturbative gravitational production in this regime. For steeper potentials ($n>2$), however, we identify a sizable contribution arising from the non-adiabatic transition between inflation and reheating. This component is naturally incorporated in the Bogoliubov formalism but absent in the Boltzmann description, and we show that it is important over a broad range of momenta. We derive analytic approximations within both frameworks that clarify the physical origin and scaling behavior of the spectrum. Our results delineate the regime of validity of Boltzmann approaches and show that, for steeper inflaton potentials, graviton production is governed by non-adiabatic transition dynamics for which the Bogoliubov formalism provides the most appropriate description.

The observed unusual behaviors of the orbits of Trans-Neptunian objects as well as the gravitational anomalies detected by the Optical Gravitational Lensing Experiment can be explained by assuming the existence of a ninth planet in the Solar System, having a mass of the order of $5-10M_{\oplus}$, and located at the distance of 300-1000 AU from the Sun. Since no optical counterpart of Planet 9 was observed, it is reasonable to assume that it has a very low luminosity. Various proposals on the nature of Planet 9 have been advanced, including the possibility that it is a black hole, an axion or a dark matter star. We propose that dark matter heating of Planet 9 could generate a thermal radio flux that could allow its observational detection, even if Planet 9 is a very dark object. We estimate the dark matter impact parameter, the mass and the kinetic energy deposition rates, as well as the surface temperature of Planet 9. By adopting a specific model for the time evolution of the planet, and assuming a long time capture of dark matter, the surface temperature of Planet 9, and the spectral features of the emitted radiation are obtained. Our results indicate that dark matter capture may provide an efficient mechanism for the heating of Planet 9, and also provide a specific observational signature of the planet. The numerical evaluations depend on the unknown value of the dark matter-ordinary matter interaction cross-section, with the estimates obtained as a function of its ratio and the saturation cross section for dark matter to deposit its entire energy. For a value of this ratio of $10^{-10}$, and for a dark matter density of the order of $1.32\times 10^{-17}$ g/cm$^3$, in a few Gyrs the surface temperature of Planet 9 can reach values of the order of 200 K, or even higher, with a maximum wavelength of around $\lambda_{max}=1.44\times 10^{-3}$ cm, situated in the infrared domain.

The radial acceleration relation reveals a nearly universal acceleration scale of order $10^{-10}\,\mathrm{ms^{-2}}$ in galactic dynamics, whose origin remains unexplained within conventional cold dark matter scenarios. We propose that this scale arises from an intrinsic infrared spectral property of the dark sector. Specifically, we hypothesize that a long-lived, color-neutral gluonic vacuum component survives the post-inflationary expansion era and, at large distances, develops a spectrally rigid lowest-weight structure. The microscopic seed for this infrared organization is provided by the QCD trace anomaly, which breaks classical scale invariance and, through dimensional transmutation, generates an intrinsic infrared scale in the gluonic sector. Requiring Lorentz covariance together with a positive-energy lowest-weight unitary realization then selects the Anti de Sitter algebra $\mathfrak{so}(2,3)$ as the simplest symmetry admitting a discrete tower of states with a representation-theoretically protected gap. The associated gap introduces a finite correlation length $r_{\texttt{c}}$ that controls the large-scale coherence of the dark sector. A self-gravitating condensate dominated by the lowest-weight mode generates a characteristic acceleration $g^{}_\star = G M_h / r_{\texttt{c}}^2$, naturally of the same order as the observed galactic acceleration scale, within standard Newtonian gravity. In this framework, the galactic acceleration scale appears as the gravitational imprint of a trace-anomaly-seeded infrared spectral gap in a coherent gluonic dark sector, rather than as a consequence of modified gravity or of galaxy-by-galaxy formation histories.

We investigate the cosmological implications of non-polynomial quasi-topological gravity (NPQTG), a novel class of modified gravitational theories in which the background dynamics is encoded in a single function of the Hubble parameter. This framework provides a minimal and theoretically consistent extension of general relativity, incorporating higher-curvature effects while preserving second-order field equations and avoiding higher-derivative instabilities. We first establish the general conditions for cosmological viability and construct explicit realizations, including polynomial, quartic, power-law and non-polynomial models, demonstrating how different functional forms lead to distinct expansion histories. Focusing on the quartic and power-law cases, we show that the resulting cosmological evolution reproduces the standard thermal history of the Universe and gives rise to an effective dark-energy sector of geometric origin, with dynamical equation-of-state behavior that can lie in the quintessence or phantom regime. We then confront the models with observational data from Type Ia Supernovae, Cosmic Chronometers, and Baryon Acoustic Oscillations, using a Bayesian MCMC analysis. We find that both models provide an excellent fit to the data, remaining fully compatible with current constraints and statistically competitive with $\Lambda$CDM. Our results demonstrate that NPQTG offers a simple and efficient framework for describing late-time cosmic acceleration with dynamical dark energy, while maintaining theoretical consistency and observational viability.