Papers

We present theoretical predictions for solar-like oscillators in the pre-main sequence phase of stellar evolution. Our pre-main sequence models start from a stellar seed of 0.01 solar masses that gains mass through accretion, offering an alternative description to the classical approach segmented into the Hayashi and Henyey tracks. Evolutionary models are calculated using the \mesa stellar evolution code with a custom accretion routine and pulsation properties are investigated using the \GYRE oscillation code. We present evolutionary tracks and internal structures for accreting pre-main sequence solar-like stars in the mass range from 0.7 to 1.6 solar masses, adopting 35 mass accretion histories previously extracted from two-dimensional magneto-hydrodynamical simulations. Atmospheric parameters of our models constrain characteristic frequencies of pre-main sequence solar-like oscillators to be generally greater than 500 $\mu\text{Hz}$. We highlight the imprint of accretion on the buoyancy and Lamb profiles and illustrate the effects on the small- and large frequency separations. We additionally quantify individual frequency differences across the 35 accretion histories at the zero-age main-sequence, showcasing differences no larger than $20 \ \mu\text{Hz}$ for an exemplary model. Finally, we discuss the potential of detecting solar-like oscillations in pre-main sequence stars with the upcoming ESA PLATO mission.

A hybrid PIC-fluid model is proposed for three dimensional numerical simulation of laser-plasma interaction. Ions are treated kinetically, electrons as a ten-moment fluid, capturing ion-scale dynamics, pressure anisotropy, and non-Maxwellian distributions efficiently. A laser-envelope model handles energy deposition and ponderomotive heating without resolving optical oscillations. Collisional and ionisation processes ensure self-consistent evolution of energy and charge states. The model is implemented in the AKAM code, providing a scalable framework that bridges fully kinetic and fluid approaches for high-energy-density and laboratory plasma applications.

Correctly interpreting JWST spectra of close-in exoplanets requires a measurement of the X-ray and ultraviolet light that the planets receive from their host stars. Here we provide spectral energy distributions (SEDs) covering the range $\approx5-1\times10^7$A for 20 transiting exoplanet host stars observed in JWST Cycle 1. The SEDs are constructed out of new and archival Hubble Space Telescope, Chandra X-ray Observatory and/or XMM-Newton data combined with spectra from models or stars with similar properties (proxies) filling in unobserved gaps. We have also constructed SEDs of likely Habitable Worlds Observatory targets $\kappa^1$ Ceti, $\tau$ Ceti, $\epsilon$ Indi and 70 Oph B for use as proxies. We find that the JWST target planets almost all experience much stronger ultraviolet fluxes than the Earth, especially in the extreme ultraviolet, even for planets with similar overall instellation. Strong ongoing or past atmospheric escape is possible for a majority of these planets. We also assess the now considerable sample of panchromatic stellar SEDs and its applicability for current JWST observations and beyond.

In gravitational lensing, the Mass-Sheet Transformation (MST)-or mass-sheet degeneracy-leaves image positions unchanged while scaling magnifications and time delays. The transformation scales the lens mass distribution and superposes a uniform mass sheet, but this formulation offers no clear physical interpretation. Here I show that the MST follows directly from a scaling symmetry that becomes apparent when the ray-trace relation is written in proper-distance coordinates. In this form, the ray-trace relation isolates a geometric focusing term. Subtracting this term from the deflection law defines the Image-Selection Relation (ISR), which determines image positions, magnifications, and differential time delays. The ISR exhibits a scaling symmetry that leaves image positions unchanged while scaling magnifications and time delays. Restoring the geometric focusing term then gives a ray-trace relation related to the original one by the Mass-Sheet Transformation.

Star-gas interactions can provide gravitational feedback that influences the dynamical evolution of stellar clusters, through processes such as dynamical friction (DF) and its non-dissipative counterpart, negative dynamical friction (NDF). Using the PeTar code, we perform direct $N$-body simulations of an open cluster initially containing $10^4$ stars, evolving within a gaseous medium spanning a range of ambient densities. Our results demonstrate that NDF associated with stellar outflows interacting with the surrounding gas can enhance the rate of cluster expansion, preferentially transporting stars toward the cluster outskirts. This behavior is accompanied by a more rapid decline in the number of binaries composed of a neutron star and a main-sequence star. A statistical analysis of binary orbital parameters further indicates that, compared to DF-dominated evolution, NDF tends to retain systems with larger semi-major axes and lower eccentricities. Outflow-ambient gas interactions can modify the dynamical processing of binaries in star clusters, leading to changes in the survival fraction and composition of the remaining binary population.

This paper introduces a novel technique to preserve spectral features in lossy compression based on a novel fast Fourier correction algorithm\added{ for regular-grid data}. Preserving both spatial and frequency representations of data is crucial for applications such as cosmology, turbulent combustion, and X-ray diffraction, where spatial and frequency views provide complementary scientific insights. In particular, many analysis tasks rely on frequency-domain representations to capture key features, including the power spectrum of cosmology simulations, the turbulent energy spectrum in combustion, and diffraction patterns in reciprocal space for ptychography. However, existing compression methods guarantee accuracy only in the spatial domain while disregarding the frequency domain. To address this limitation, we propose an algorithm that corrects the errors produced by off-the-shelf “base” compressors such as SZ3, ZFP, and SPERR, thereby preserving both spatial and frequency representations by bounding errors in both domains. By expressing frequency-domain errors as linear combinations of spatial-domain errors, we derive a region that jointly bounds errors in both domains. Given as input the spatial errors from a base compressor and user-defined error bounds in the spatial and frequency domains, we iteratively project the spatial error vector onto the regions defined by the spatial and frequency constraints until it lies within their intersection. We further accelerate the algorithm using GPU parallelism to achieve practical performance. We validate our approach with datasets from cosmology simulations, X-ray diffraction, combustion simulation, and electroencephalography demonstrating its effectiveness in preserving critical scientific information in both spatial and frequency domains.

Plateau features are frequently observed in the afterglows of gamma-ray bursts (GRBs), yet their physical origins remain under debate. In this work, we compile a sample of 124 GRBs with known redshifts and simultaneous X-ray and optical afterglow observations. We categorize them into four subsets based on the existence of plateaus and the bands in which they appear. Namely, Dataset 1: plateaus are detected simultaneously in both X-ray and optical bands (75 bursts); Dataset 2: plateaus are only in X-rays (15 bursts); Dataset 3: plateaus appear only in the optical (17 bursts); Dataset 4: no plateaus in either band (17 bursts). We employ these datasets to test the applicability of the energy-injection model by examining whether the temporal decay index $\alpha$ and the spectral index $\beta$ of GRB afterglows simultaneously satisfy the closure relations in X-ray and optical bands. We find that 47 bursts of Dataset 1 simultaneously obey the closure relations in both bands under the conditions of the electron spectral index $p>2$ and the injection parameter $q\in (0, 0.5)$, and 69 of the dataset for $p>1$ and $q\in (0, 0.8)$, providing a strong support for the energy-injection interpretation. However, for Datasets 2 and 3, although $\alpha$ and $\beta$ of the plateaus mostly satisfy the closure relations, those in the other band show significant deviations, which implies that bursts with a single-band plateau are inconsistent with the interpretation of energy injection. Furthermore, we also compare the isotropic X-ray energy of plateaus with the rotational energy budget of millisecond magnetars.

We report the discovery of giant pulse (GP) emission from the transitional millisecond pulsar (tMSP) PSR J1227$-$4853, using 174 hours of single-pulse data from the upgraded Giant Metrewave Radio Telescope (uGMRT). This marks the first detection of GPs from a transitional MSP and adds to the small number of millisecond pulsars known to exhibit such extreme variability. A total of 235 GPs were detected across observations at 550-750 MHz, with widths as narrow as 1.28 $\mu$s and flux densities up to $\sim 10^4$ times the pulsar's mean flux density. The GPs are strongly localized in pulse phase, originating predominantly from the second and third main-pulse components, and are absent in the inter-pulse region. Their cumulative fluence distribution follows a power law above the completeness threshold, consistent with a defining characteristic of GP emission. The arrival times of the GPs deviate significantly from Poisson statistics, with the waiting-time distribution well described by a Weibull model having a shape parameter of $k = 0.30$, indicative of strong temporal clustering. During an epoch of enhanced activity, the GP rate increased by nearly two orders of magnitude to 124 $\mathrm{hr}^{-1}$, with a corresponding shape parameter of $k = 0.47$. This value is similar to that reported for a burst storm from the repeating fast radio burst FRB 20200120E, suggesting possible phenomenological parallels between GPs from compact binary systems and repeating FRBs.

Radio surveys of ultraluminous X-ray sources (ULXs) allow us to find supercritically accreting compact objects (SS 433/W50 like systems) or stripped nuclear black holes in nearby galaxies. We identified 21 such objects by crossmatching a ULX catalog with the Rapid ASKAP Continuum Survey (RACS) and Very Large Array Sky Survey (VLASS). They may have a diverse population. (i) Three have a double lobed radio structure with a compact core found in two of them, and could be quasars. (ii) Five are associated with extended radio structure and star forming regions in optical, where the radio emission is likely due to star forming activities, although the steep radio spectrum up to several GHz casts doubt on that. Two of them show X-ray variability suggesting that they are ULXs embedded in star forming regions. (iii) Thirteen are associated with an unresolved radio source, with a steep spectrum seen in eight, a flat or inverted spectrum seen in two. Those with a steep spectrum are arguably candidates for SS 433/W50 like objects, with radio emission due to optically thin synchrotron radiation in a surrounding jet/wind powered nebula. Remarkable cases include NGC 925 ULX1 and NGC 6946 ULX1, which are associated with an optical nebula. Those with a flat or inverted spectrum could be accreting black holes with a compact jet, while the black hole mass is estimated to be several $10^6 - 10^8$ $M_\odot$ based on the fundamental plane. Redshift measurements are needed to firmly determine the association with their apparent host galaxy.

IceCube observations point to Active Galactic Nuclei (AGN) as promising contributors to the observed astrophysical neutrino flux. Close to the central black hole, protons can be accelerated through magnetic reconnection to very high energies and subsequently interact with abundant X-ray photons in the source, leading to neutrino production. We investigate whether the diffuse neutrino flux observed by IceCube can originate, via proton acceleration, in reconnection-powered coronae of non-jetted AGN. We create a library of neutrino spectral templates, over a large grid of values for the three key model parameters: the proton plasma magnetization of the corona $\sigma_{\rm p}$, the X-ray coronal luminosity, and the black hole mass. Synchrotron cooling of pions and muons plays a significant role due to the large coronal magnetic fields. We couple the single-source model with a mock AGN catalog, consistent with the observed X-ray and mid-infrared AGN samples at redshifts $z=0-4$, to infer the diffuse neutrino flux. Coronal emission satisfactorily explains the most recent IceCube measurements of the diffuse neutrino flux up to energies of $\sim 1$~PeV, provided that $\sim$10% of the AGN coronae have $\sigma_{\rm p} \sim 10^5$, while the rest are distributed over a range of lower magnetizations. Coronal emission is suppressed at higher energies by pion and muon cooling, so that another population is required, with jetted AGN being strong candidates.

Cosmology has entered an era of unprecedented precision, yet increasing accuracy has revealed cracks in the standard $\Lambda$CDM paradigm. Although the model remains highly successful when confronted with individual datasets, joint analyses expose a network of tensions involving the Hubble constant, CMB lensing, curvature, neutrino masses, and the nature of dark energy. In this contribution to the 3rd General Meeting of the COST Action COSMIC WISPers (CA21106), within the context of Working Group~2, we critically assess these discrepancies, emphasizing the role of model assumptions, parameter degeneracies, and dataset consistency. We review proposed early- and late-time solutions, discuss how recent DESI BAO results alter the viability of late-time extensions, and explore interacting dark-sector scenarios. Our analysis highlights the need for caution in interpreting cosmological measurements and underscores the importance of internal consistency among cosmological probes before claiming percent-level accuracy or invoking new physics.

The numerical calculation of optical properties (extinction, absorption, scattering and polarisation efficiencies) is often time-consuming for non-spherical and inhomogeneous particles. Where possible analytical methods are therefore to be preferred. We provide an analytical tool to derive the optical properties of mantled spheroidal particles, of arbitrary axis ratio, in the long wavelength limit (a << lambda), where the mantle form may be confocal, co-axial or of constant depth with respect to the particle core. We have developed an analytical approach to spheroidal core/mantle particle optical property calculations. The analytical method compares well with DDSCAT numerical calculations and, under limited circumstances, with those made using the Bruggemann effective medium theory (EMT).The analytical method presented here provides a useful tool to explore the optical and polarisation properties of core/mantle spheroidal particles at long wavelengths (lambda >~ 8mu) and is simpler and faster to implement than corresponding numerical methods. We caution against the use of EMT methods in approximating the optical properties of core/mantle particles.

We present a systematic investigation of X-ray spectral variability of Seyfert 1 galaxies using a “spectral-ratio model fitting” technique, which we developed to estimate contribution of the putative clumpy absorbers to the spectral variations. Archival XMM-Newton observations of 12 active galactic nuclei were analyzed to constrain properties of these absorbers. Our analysis demonstrates that the soft X-ray variability is primarily governed by fluctuation of the partial covering fraction of mildly ionized clumpy clouds. In particular, for Mrk 335, PDS 456, and 1H 0707-495, outflow velocities of the clumpy absorbers are constrained from the blue-shifts of the Fe-L edge structure. The blue-shifted Fe-L edge successfully reproduces the well-known complex spectral feature near 1 keV in 1H 0707–495, which was often explained by invoking an ad hoc absorption structure. Notably, the inferred outflow velocities of the clumpy absorbers are comparable to, or even exceed, those associated with the Ultra-Fast Outflows (UFOs). Furthermore, we found a positive correlation between the outflow velocities and the intrinsic X-ray fluxes in two of four data sets, and the remaining two datasets also agree with this positive correlation, which supports a radiative-driven wind scenario that the X-ray/UV emission from the central black holes is causing the UFOs and the outflowing clumpy absorbers. In addition, the line-driven acceleration is likely playing a significant role, since the line opacities of the clumpy absorbers are highly sensitive to the flux changes. These findings provide a robust observational support for the “hot inner and clumpy outer wind” paradigm, suggesting a common origin for both the UFOs and the clumpy absorbers.

Context: Quantitative spectroscopy of luminous blue stars relies on detailed non-LTE model atmospheres whose increasing physical realism makes direct, iterative analyses computationally demanding. Aims: We introduce MAUI (Machine-learning Assisted Uncertainty Inference), a statistical framework designed for efficient Bayesian inference of stellar parameters using emulator-based spectral models. Methods: MAUI employs Gaussian-process-based emulators trained on a limited set of non-LTE simulations, combined with Markov Chain Monte Carlo (MCMC) sampling to explore posterior distributions. We validate the approach with recovery experiments and demonstrate it on Galactic late-type O dwarf and early-type B dwarf/subgiant stars. Results: The emulator reproduces the predictions of full atmosphere models within quoted uncertainties while reducing computational cost by orders of magnitude. Posterior distributions are well calibrated, with conservative coverage across all stellar parameters. Conclusions: Emulator-driven Bayesian inference retains the accuracy of classical analyses at a fraction of the computational expense, enabling posterior sampling that would be prohibitive with direct model evaluations. This positions emulators as a practical tool for high-fidelity spectroscopy of massive stars as atmosphere models grow more demanding.

The rapid depletion of dust particles in protoplanetary disks limits the time available for planetesimal formation, as solids are typically accreted onto the central star before dust particles can undergo substantial growth. Dust traps formed at sharp viscosity transitions $-$ such as at the edges of the accretionally inactive dead zones $-$ can halt radial drift and enhance dust coagulation. In this study, dust dynamics is investigated using RAPID, a one-dimensional Lagrangian-Eulerian simulation code that tracks representative particle trajectories over time. In order to explore the effect of physical parameters on dust evolution, a grid of 243 models was run. The simulation grid covers a range of parameters such as viscosity, width of the transition region at the edges of the dead zone, disk surface density exponent, and the collisional fragmentation velocity of the dust particles. The computational domain extends from 1 to 50 AU and covers $5\times10^5$ years of disk evolution, assuming a disk mass of $\sim 0.005\,M_\odot$. The results show that pressure maxima can trap up to $3-10\,M_\oplus$ of dust, depending on the local disk conditions. However, increasing the fragmentation velocity, decreasing the viscosity, or widening the dead zone transition width tends to reduce the effectiveness of dust trapping. The simulation results with RAPID reveal that dust evolution is highly sensitive to the physical conditions of the disk, which governs the early stages of planetesimal growth.

The life-cycle, structure, and dynamics of the interstellar medium (ISM) is regulated by turbulence. Complex physical processes, including supernova (SN) explosions, shear, and gravitational collapse, drive and maintain turbulence, but it is still an open question what turbulence driving mode is primarily excited by these different mechanisms. The turbulence driving parameter, b, can be used to quantify the ratio of solenoidal to compressive modes in the acceleration field that drives the turbulence. Compressive driving is characterised by b ~ 1, while purely solenoidal driving gives b ~ 0.3. To quantify the turbulence in the galactic ISM, we investigate the time evolution of b, as well as the turbulent Mach number, and plasma beta (thermal-to-magnetic pressure ratio), and its correlation with star formation in the magnetised warm neutral medium (WNM) of the TIGRESS shearing-box simulations of a kpc-sized patch of a Milky-Way-like galaxy, over a 100 Myr time period (~ half an orbital time). In this simulation the turbulence is driven by a combination of shear, gravitational collapse, and star formation feedback in the form of radiation and SNe. We find that the turbulence driving parameter fluctuates in time between b ~ 0.4 and b ~ 1. We find a time-dependent correlation of b with star formation activity, such that high star formation rates follow about one turbulent turnover time (~ 10 Myr) after phases of highly compressive driving (b > 0.5). About 20 Myr after the peak in star formation, type-B SN feedback drives up the WNM fraction and turbulent Mach numbers, and reduces plasma beta and the driving to b ~ 0.4-0.5.

Neutron star mergers hold the key to several grand challenges of contemporary (astro-)physics. In view of the upcoming next generation of ground-based detectors, it is crucial to keep improving theoretical predictions to harvest the full scientific returns from these investments. We introduce here a substantial update of our Lagrangian numerical relativity code SPHINCS_BSSN. Apart from changing our unit system, we add constraint damping terms to the BSSN spacetime evolution equations. We demonstrate that this measure reduces, without noteworthy computational cost, the Hamiltonian constraint violations by more than an order of magnitude. We further implement contributions to thermal energy and pressure that are based on Fermi liquid theory and contain a parametrization of the Dirac effective mass. These terms can be combined with any cold equation of state, and they enhance the physical realism of our simulations and introduce a physics-based concept of a temperature. In a set of merger simulations, we demonstrate good agreement with other temperature-dependent numerical relativity simulations. We find that different parametrizations of the Dirac effective mass can translate into shifts of $\sim 150$ Hz in the dominant post-merger gravitational wave peak frequency.

Heavy Weakly Interacting Massive Particles (WIMPs) remain a prominent yet less constrained dark matter (DM) candidate, with the Galactic Centre (GC) serving as a prime target for indirect detection via gamma-ray signals. Extending our previous work that highlighted the significance of secondary inverse Compton (IC) emission from annihilation-produced electrons, we expand the analysis to a broader range of WIMP masses and introduce a more realistic spatially-dependent modelling framework for the GC environment. This approach incorporates complexities such as the three-dimensional DM distribution, spatially varying radiation and magnetic fields, and electron transport mechanisms like Galactic winds and diffusion. We assess the impact of these environmental factors on both the spatial and spectral characteristics of the resulting secondary emissions. Our results demonstrate the robustness and necessity of incorporating this emission, and highlight its role in enhancing the prospects for detecting heavy WIMPs through observations of the inner Galaxy. We provide the resulting data products to the community to support future analyses and observational studies.

The detection and reconstruction of gravitational waves from core-collapse supernovae (CCSN) present significant challenges due to the highly stochastic nature of the signals and the complexity of detector noise. In this work, we introduce a deep learning framework utilizing a ResNet-50 encoder pre-trained via supervised contrastive learning to classify CCSN signals and distinguish them from instrumental noise artifacts. Our approach explicitly optimizes the feature space to maximize intra-class compactness and inter-class separability. Using a simulated four-detector network (LIGO Hanford, LIGO Livingston, Virgo, and KAGRA) and realistic datasets injecting magnetorotational and neutrino-driven waveforms, we demonstrate that the contrastive learning paradigm establishes a superior metric structure within the embedding space, significantly enhancing detection efficiency. At a false positive rate of $10^{-4}$, our method achieves a true positive rate (TPR) of nearly $100\%$ for both rotational and neutrino-driven signals within a distance range of $10$–$200$~kpc, while maintaining a TPR of approximately $80\%$ at $1200$~kpc. In contrast, traditional end-to-end methods yield a TPR below $20\%$ for rotational signals at distances $\geq 200$~kpc, and fail to exceed $60\%$ for neutrino-driven signals even at a close proximity of $10$~kpc.

Ejecta from core-collapse supernovae interact with the circumstellar medium shed by the progenitor star, producing X-ray emission. Previous studies analyzed the X-ray spectrum of the Type IIb supernova SN 2011dh up to 500 days after explosion. Long-term monitoring of X-ray emission provides valuable constraints on supernova evolution and progenitor systems, yet such studies remain rare for Type IIb events due to limited data. Here we present the most comprehensive X-ray light curve of SN 2011dh to date, combining all available Chandra and XMM-Newton data with previously published and newly released Swift observations, extending coverage to 5100 days. We measure a luminosity decline proportional to t$^{-0.74 \pm 0.04}$ and infer a mass-loss rate of $(1.0-2.2) \times 10^{-6}$ solar masses per year for $v_w = 10$ km/s, or $(2.0-4.4) \times 10^{-6} $ solar masses per year for $v_w = 20$ km/s. These estimates agree with earlier results, supporting the interpretation that the X-ray emission has been dominated by an adiabatic reverse shock. The consistency of our late-time results with previous studies demonstrates that SN 2011dh has evolved steadily for nearly 14 years.

Comprehensive cosmological analysis of an effective non-standard dark matter(NSDM) model, characterized by an equation of state $w_{\mathrm{dm}} = w_2 a^2$, which allows for mild deviations from the previously assumed pressureless cold dark matter, is elaborated in the present work. This effective description framework is the scenarios that matter contents coupled to three distinct single-parameter dynamical dark energy models: i.e, the thawing scalar field, the Modified Emergent Dark Energy(MEDE) scenario, and the constant-$w$ model. We constrain these frameworks by using the latest cosmological probes, including the Planck 2018 Cosmic Microwave Background(CMB) distance priors, the Baryon Acoustic Oscillation(BAO) measurements from the Data Release 2 of the Dark Energy Spectroscopic Instrument(DESI), and three compilations of Type Ia Supernovae(SN Ia) namely the Dark Energy Survey Year 5 (DESY5) compilation, the Union3 compilation, and the PantheonPlus (PP) sample. Across all three dark energy scenarios and all dataset combinations, we find a consistent preference for negative values of the parameter $w_2$. Furthermore, this result is robust against the choice of dark energy parametrization, suggesting a model-independent deviation from "standard" cold dark matter. This result indicates that the dark matter fluid possesses a small but non-vanishing negative pressure, meaning a non-cold nature. While the inferred Hubble constant $H_0$ remains consistent with the Planck $\Lambda$CDM value and does not fully alleviate the $H_0$ tension with local measurements, the persistent detection of $w_2 < 0$ across a wide range of independent cosmological probes provides compelling evidence for new physics in the dark matter sector – suggesting that dark matter may be better described as an effective fluid endowed with a mild negative pressure, rather than as a perfectly cold, pressureless substance.

We present multiband photometric and spectroscopic observations of supernova (SN) 2024abvb, which exhibits early-time prominent photoionized narrow emission lines of C II superposed on a blue continuum. The absence of Balmer features indicates that the SN exploded within hydrogen-poor circumstellar matter (CSM). Together with the lack of explicit evidence of helium signatures, we tentatively identify SN 2024abvb as a Type Icn SN (SN Icn). After correcting for extinction, we estimate an r-band peak absolute magnitude of -19.7, placing SN 2024abvb in the luminous regime of SNe Icn. We adopted a hybrid model that accounts for both the energy released by the ejecta-CSM interaction and the radioactive decay of nickel synthesized in the SN ejecta to fit the light curve of SN 2024abvb. The best-fit model to the multiband light curves within the first ~ 40 days after explosion suggests that the CSM, radioactive nickel, and ejecta masses to be 0.28 Msun, < 3.8 * 10^-2 Msun, and 0.12 Msun, respectively. Such a low ejecta mass indicates that the progenitor star of SN 2024abvb experienced a significant mass-stripping process, consistent with the hydrogen-poor and helium-poor spectral features. SN 2024abvb provides important insights into the physical origins of the rare subclass of SNe Icn.

Surface thermodynamics of minerals influence their properties and occurrence in both terrestrial and planetary systems. Using high-temperature oxide melt solution calorimetry, we report the first direct measurement of the surface energy of enstatite, MgSiO$_3$. Enstatite nanoparticles of different sizes were synthesized using the sol-gel method, characterized with X-ray diffraction, thermal analysis, infrared spectroscopy, surface area measurements, and electron microscopy. The materials consist of crystallites with sizes of $\sim $10 - 20 nm, which are agglomerated into larger nanoparticles. Thus, both surface and interface terms contribute to the measured enthalpies. Analysis based on calorimetry and calculated surface and interface areas gives the surface enthalpy of enstatite as 4.79 $\pm$ 0.45 J m$^{-2}$. This value is comparable to that of forsterite (Mg$_2$SiO$_4$) and larger than those of many nonsilicate oxide materials. This large surface energy may present a barrier to the nucleation of enstatite in planetary atmospheres and other geochemical and planetary environments. The interfacial energy of enstatite appears to be close to zero. The transition enthalpy from bulk orthoenstatite to bulk clinoenstatite is 0.34 $\pm$ 0.93 kJ mol$^{-1}$, which is in agreement with earlier reports. The methodology developed here can be extended to other materials having complex structures and morphologies to separate surface and interfacial contributions to energetics.

In-space manufacturing is essential for achieving long-term planetary colonization, particularly on Mars, where material transport from Earth is both costly and logistically restrictive. Traditional subtractive manufacturing methods are highly equipment-, energy-, and material-intensive, making additive manufacturing (AM) a more practical and sustainable alternative for extraterrestrial production. Among various AM technologies, selective laser melting (SLM) stands out due to its exceptional versatility, precision, and capability to produce dense metallic parts with complex geometries. However, conventional SLM processes rely heavily on inert argon environments to prevent oxidation and ensure high-quality part formation, conditions that are difficult to reproduce on Mars. This study investigates the feasibility of using carbon dioxide (CO2), which makes up over 95% of the Martian atmosphere, as a potential substitute for argon in SLM. Single-track and two-dimensional 316L stainless steel specimens were fabricated under argon, CO2, and ambient air environments with a wide range of laser parameters to evaluate the influence of atmospheric composition on surface morphology, microstructural cohesion, and oxidation behavior. The results reveal that no single parameter controls the overall part quality; rather, a balance of parameters is essential to maintain thermal equilibrium during fabrication. Although parts produced in CO2 exhibited slightly inferior surface finish, cohesion, and oxidation resistance compared to argon, they performed significantly better than those fabricated in ambient air. These findings suggest that CO2-assisted SLM could enable sustainable in situ manufacturing on Mars and may also serve as a cost-effective alternative shielding gas for terrestrial applications.

We present a complete analytic and semi-analytic study of gravitational collapse and primordial black hole (PBH) formation in the quadratic $f(R)$ model $f(R)=R+\alpha R^2$. We first derive the perturbative expansion around General Relativity (GR), working to first order in the small parameter $\alpha$. For a collapsing flat FLRW dust interior we compute the explicit first-order corrections to the scale factor, the stellar radius, and the horizon formation time. { We then use these results to infer the expected trend in the PBH formation threshold $\delta_c$, rather than a direct quantitative determination. Within this perturbative framework, the quadratic correction modifies the dust collapse dynamics at first order, while the flat radiation-dominated background does not receive a nontrivial correction at the same order. As result, any modification of PBH formation in the radiation era must arise from nonlinear or non-perturbative effects. The perturbative analysis therefore provides qualitative insight into how curvature corrections influence collapse, particularly in high-curvature regimes.} To access this regime we reformulate the theory in the Einstein frame, where the model becomes GR plus the scalaron field $\phi$ with the Starobinsky potential. We provide the complete ODE system governing both the cosmological background and the evolution of an overdense closed FLRW patch. This system can be numerically integrated to obtain the critical overdensity $\delta_c(k)$ for PBH formation near the end of inflation.

In this paper we study the properties of Kasner cosmological solutions in Lovelock gravity. Recent progress in the investigation of flat cosmological models in Lovelock gravity unveiled the fact that in quadratic (Gauss–Bonnet) and cubic Lovelock gravities, the higher-order power-law solutions could play the role of both future and past asymptotes, and under some conditions, there could exist a smooth transition between them. So it is natural to question if this feature is unique to Gauss–Bonnet and cubic Lovelock gravities, or if it is a general feature of Lovelock gravity. Our analysis suggests that starting from quartic and in all higher-order Lovelock gravities, the high-order Kasner solution cannot play the role of a past asymptote, not only preventing the abovementioned transition from happening, but also potentially hindering the possibility of reaching viable compactification.

We present results from a seven-season (2018-2024) monitoring campaign of the gravitationally lensed quasar system PS J2305+3714 using the 1.5-m Maidanak Telescope in the optical R-band. From these data, the amplitude of possible microlensing variability does not exceed 10 mmag on a 7-yr timescale. Additionally, we measure a time delay of $t_{AB}$ = 52.2$\pm$2.5 days, with the brighter image A leading. Long-slit \WHT spectroscopy refines the quasar redshift to $z_s$ = 1.791 and provides the first measurement of the lens redshift, $z_d$ = 0.473. The flux ratios of the quasar images in the MgII $\lambda$2800 emission line and in the adjacent continuum are nearly identical, indicating minimal microlensing effects in the spectral domain, which is consistent with the very weak microlensing signal in the time domain. Using precise astrometry from recent HST imaging and the MgII flux ratio, we also built two simple mass models for the lens system. The close agreement between the measured delay and those predicted by the mass models, measured redshifts, and a concordance $\Lambda$CDM cosmology, confirms the robustness of our results and highlights PS J2305+3714 as a promising system for future time-delay cosmography.

This article reviews the emerging field of exo-geoscience, focusing on the geological and geophysical processes thought to influence the evolution and (eu)habitability of rocky exoplanets. We examine the possible roles of planetary interiors, tectonic regimes, continental coverage, volatile cycling, magnetic fields, and atmospheric composition and evolution in shaping long-term climate stability and biospheric potential. Comparisons with Earth and other planets in the Solar System highlight the diversity of planetary conditions and the rarity of conditions relevant to life. We also discuss contingency and convergence in planetary and biological evolution as they relate to the spread of life in the universe. The observational limits of current and planned missions are assessed, emphasizing the need for models that connect internal dynamics to detectable atmospheric and surface signatures as well as the need for laboratory measurements of planetary properties under a wide range of conditions. The large number of exoplanets promises opportunities for empirical and statistical studies of processes that may have occurred earlier in Earth's history, as well as of the other pathways rocky planets and biospheres may take. Thus, exo-geoscience provides a framework for interpreting exoplanet diversity and refining strategies for detecting life beyond the Solar System.

We investigate induced Compton scattering of a circularly polarized Alfvén wave propagating in a magnetized electron-positron pair plasma using one-dimensional Particle-in-Cell (PIC) simulations. In this system, two distinct modes of density fluctuations, referred to as the charged mode and the neutral mode, are theoretically expected to arise through parametric instabilities. Our simulations confirm these predictions: in the charged mode, the electron and positron densities fluctuate oppositely (Langmuir-like), while in the neutral mode, the charge is Debye-screened and both species fluctuate in phase (acoustic-like). The linear growth rates obtained from the simulations are in good agreement with analytical estimates for both modes. We also find that, in some cases, the linear growth saturates before full scattering occurs, allowing the incident wave to propagate without significant attenuation. Our results allow us to determine whether induced Compton scattering grows linearly in magnetized pair plasmas, offering a foundation for studies of fast radio bursts and laser-plasma experiments.

Fluctuation dynamos provide a robust mechanism for amplifying weak seed magnetic fields in turbulent astrophysical plasmas. However, their behaviour in the highly compressible regimes characteristic of the interstellar medium remains incompletely understood. Using high-resolution 3D magnetohydrodynamic simulations of supersonic turbulence with rms Mach number $\mathcal{M}_{\rm rms} \approx 11$, we explore fluctuation dynamos across magnetic Prandtl numbers ${\rm Pm} = 1-10$. At ${\rm Pm}=1$, dynamo growth is slower and saturates at lower magnetic-to-kinetic energy ratios, with amplification in the kinematic phase dominated by compression rather than line stretching. In contrast, at ${\rm Pm}=10$, vortical stretching emerges as the dominant mechanism, yielding faster growth, higher saturation levels, and stronger suppression of density–magnetic field correlations by magnetic pressure. This transition is reflected in the correlation coefficient between density and magnetic field strength, which is strongly positive at ${\rm Pm}=1$ but decreases significantly at higher ${\rm Pm}$. Across all runs, the ratio of velocity-to-magnetic integral scales is $\sim 3.4$, in the saturated phase, independent of ${\rm Pm}$, while the ratio of viscous to resistive dissipation scales increases with the increase in ${\rm Pm}$. Synthetic Faraday rotation measures reveal coherence lengths of $\sim$one-fourth to one-third of the forcing scale across the range of ${\rm Pm}$ explored. Using these coherence scales, we discuss the potential contribution of fluctuation dynamos to Faraday rotation expected from turbulent, gas-rich young disk galaxies.