Papers for Thursday, Apr 02 2026

Transient sources on astronomical photographic plates are objects that appear on a single exposure but have no counterpart in modern sky surveys or on temporally adjacent plates. I present an independent replication of two findings reported by Bruehl and Villarroel (2025) and Villarroel et al. (2025): (1) a temporal correlation between transient detections on Palomar Observatory Sky Survey (POSS-I) photographic plates and atmospheric nuclear weapons tests, and (2) a deficit of transient sources within Earth's geometric shadow cone at geosynchronous orbit altitude. Using the original dataset provided by the authors, I reproduce the chi-square contingency analysis (relative risk = 1.45, p = 0.011), extend the analysis with negative binomial regression controlling for precipitation, lunar illumination, and cloud cover (all-transient incidence rate ratio = 1.80; sunlit-only IRR = 3.98, reproducing the original paper's reported findings), and confirm temporal specificity of the association via a 10,000-iteration permutation test (p = 0.006). The Earth shadow classification identifies 499 transients (0.46%) within the umbral cone in the full catalog and 142 (0.45%) in the more stringent center-of-plate subset, both significantly below the geometric expectation of approximately 1.4%, consistent with the findings of Villarroel et al. (2025). All transients predate the launch of Sputnik 1. These results confirm the core statistical claims of the original papers based on an independent analysis.

Dwarf galaxies serve as key models for understanding galaxy assembly in the early universe, with their final properties influenced by environmental factors. Using the dark matter-only simulation "Copernicus Complexio" (COCO) and the semi-analytic model GALFORM, we examine the stellar mass assembly of dwarf galaxies across different cosmic web regions, defined by the NEXUS+/CACTUS algorithm. We identify significant variations in stellar mass assembly based on final mass, with the largest dwarf galaxies assembling, on average, 50% of their mass 7.7 Gyrs later than the smallest ones. Central galaxies also differ in their assembly from satellites of comparable final mass, forming 50% of their mass 2.5 Gyrs later. The location within the cosmic web further influences assembly, with satellite galaxies showing greater differences than centrals. Satellites in the densest regions assemble their mass 1.5 Gyrs earlier than those in the least dense regions, compared to 0.69 Gyrs for central galaxies. This disparity arises from varying infall times, with satellites in dense environments infalling 5.2 Gyrs earlier than those in voids. Additionally, we investigate the impact of reionisation parameters, specifically the timing ($z_{cut}$) and filtering scale ($v_{cut}$) of reionisation. The stellar-to-halo-mass relation shows a power law break between $10^8~\mathrm{M}_\odot < M_{200} < 10^{10}~\mathrm{M}_\odot$, with earlier $z_{cut}$ or higher $v_{cut}$ leading to more star formation suppression in lower-mass haloes. The halo occupation fraction is also affected, with later $z_{cut}$ or lower $v_{cut}$ resulting in fewer lower-mass haloes being occupied at $z=0$. Our investigation provides a valuable theoretical framework for interpreting upcoming observational data in this mass regime.

Non-cold dark matter particles can arise from the evaporation of primordial black holes (PBHs). In this paper, we further investigate how the memory-burden effect, which delays the full evaporation of black holes, affects the Lyman-$\alpha$ bound on such non-cold dark matter (NCDM) particles. We mainly focus on scenarios in which PBHs have fully evaporated by today, undergoing a semi-classical evaporation phase followed by a memory-burden dominated phase. In this framework, PBH evaporation generically leads to two distinct dark-matter populations with different velocity dispersions, which can imprint observable signatures on the matter power spectrum. We compute the resulting NCDM phase-space distribution and its impact on small-scale overdensities using the $\texttt{BlackHawk}$ and $\texttt{CLASS}$ codes. This is then used to reinterpret Lyman-$\alpha$ forest constraints for thermal warm dark matter, deriving both a velocity-dispersion-based and a matter-power-spectrum-based estimate. In particular, we discuss how we obtain constraints on scenarios in which NCDM particles constitute only a fraction of the total relic dark matter. Finally, we discuss the viable parameter space as a function of dark matter masses, PBH initial conditions, and memory-burden parameters. We show that even subdominant NCDM components from PBH evaporation can be constrained, and confirm that NCDM can only account for all of the dark matter in the absence of PBH domination, as in the semi-classical case.

Dark matter (DM) particles decaying in the Galactic halo can inject energetic $e^\pm$ that inverse-Compton scatter (ICS) solar photons into $\gamma$-rays, producing a diffuse and extended halo of emission around the Sun. We present the first quantitative study of this signal as an indirect probe of decaying DM. The intense solar photon field in the inner heliosphere amplifies the inverse-Compton emissivity by many orders of magnitude relative to the interstellar radiation field, making the Sun an unusually sensitive local converter of sunlight into $\gamma$-rays via scattering with injected $e^\pm$. Using 15 years of Fermi-LAT solar-halo data, we derive stringent limits on the DM lifetime for 10 GeV-10TeV masses at the level of $\tau_\chi \sim 10^{27}\,\mathrm{s}$ in leptonic decay channels. The predicted surface brightness rises steeply toward the Sun, and the $\gamma$-ray flux falls off at high energy due to Klein-Nishina suppression. Solar ICS $\gamma$-rays measured with degree scale angular resolution therefore provide a novel and complementary probe of DM decays, adding a local $\gamma$-ray search channel that is systematically distinct from both Galactic diffuse analyses and direct charged-particle measurements.

In this paper, we present the results of a detailed photometric analysis of Glimpse-C02, one of the most extincted globular clusters of the Milky Way. We built a deep color magnitude diagram spanning $\approx$ 10 magnitudes, enabling the first identification of the cluster's main sequence turnoff. Due to the extreme reddening affecting the region, a differential reddening correction was necessary. The resulting reddening map reveals variations up to $\delta E(B-V) \approx 2.5$ mag. From isochrone-fitting of the differential reddening corrected color-magnitude diagram, we derived a mean color excess $E(B-V)=6.33^{+0.05}_{-0.04}$, and a distance modulus $(m-M)_0=14.00^{+0.26}_{-0.11}$, corresponding to a distance of $d=6.3^{+0.8}_{-0.3}$ kpc from the Sun, and a Galactocentric distance of $2.6^{+0.6}_{-0.7}$ kpc. This distance value, within the associated uncertainties, suggests that the cluster may be located closer to the Galactic Center compared to previous estimates, possibly supporting its classification as a bulge globular cluster. We obtained a photometric metallicity estimate of [Fe/H]$=-0.30^{+0.10}_{-0.08}$ and the first absolute age determination for Glimpse-C02, resulting in $t=11.9^{+0.7}_{-0.6}$ Gyr, as typically measured for Galactic globular clusters at this metallicity. We also derived a new estimate of the center of gravity of the cluster and determined its projected density profile from resolved star counts, finding a high King concentration parameter ($c = 1.97_{-0.67}^{+0.51}$) and a core radius $r_c =8.72^{+0.40}_{-0.35}$ arcsec. Finally, from the surface brightness profile of the system, we derived an integrated $H$-band magnitude $M_{\rm H}=-7.9$, corresponding to a mass of $M=3.57^{+0.22}_{-0.19}\times 10^4 M_{\odot}$. Thus, our work classifies Glimpse-C02 as an old and metal-rich globular cluster that is in an advanced stage of its dynamical evolution.

Halo bias is typically treated as a set of coefficients in a perturbative expansion. We show instead that every point in a Gaussian density field has a well-defined scale-independent Lagrangian bias, thereby defining a bias field. This property can be extended to any linear operator acting on the Lagrangian density field, generating secondary bias fields. Halo bias then arises from geometric selection of Lagrangian patches within this pre-existing field, rather than being generated by collapse. We demonstrate that this framework predicts the measured $b(M)$ relation for halos. The multivariate Gaussian structure of the fields naturally explains the Gaussian distribution of halo bias at fixed mass and assembly bias. The results presented here motivate combining this framework with a forward model of halo collapse, yielding an ab initio model for halo clustering.

The James Webb Space Telescope provides an exciting opportunity to investigate stellar systems located in heavily obscured regions like the Galactic bulge. Possibly, the most enigmatic among them is Terzan 5: long classified as a globular cluster, it is now known to host distinct stellar populations with different iron abundances (ranging approximately from [Fe/H]=-$0.8$ to [Fe/H]=$+0.3$ dex). Indeed the chemical and structural properties collected so far suggest that it is the remnant of one of the primordial clumps that contributed to the early assembly of the bulge, a so-called "Bulge Fossil Fragment". Here we present a new photometric analysis of Terzan 5 based on JWST/NIRCam observations in the F115W and F200W filters, as well as archival HST/ACS optical (F606W and F814W) data. The dataset overcomes the severe and spatially variable extinction along the line of sight and yields the deepest color-magnitude diagram ever obtained for Terzan 5. Proper motion selections and high-resolution differential reddening corrections allow us to isolate bona fide cluster members and to provide an unprecedented view of the main-sequence turn-off region. We clearly identify two main components and determine their respective ages: the old, sub-solar component has an age of 12.5 $\pm$ 0.5 Gyr, while the super-solar component is significantly younger with an age of 4.7 $\pm$ 0.5 Gyr. Interestingly, we also find hints of an even younger main sequence turn-off and sub-giant branch, consistent with the presence of a further stellar component with an age of 3.8 $\pm$ 0.5 Gyr. There is also evidence of a blue plume populated by stars as bright as $m_{\rm F115W}\sim 17.4$, suggesting a prolonged period of star formation extending up to 2.5 Gyr ago.

Coupling stellar feedback to the evolution of individual stars, as opposed to averaging over the initial mass function (IMF), substantially improves the fidelity of galaxy formation simulations by capturing stochastic population effects. Existing treatments can typically only operate at a narrow mass resolution range, limiting their applicability. We present Imladris, a detailed model for star formation and stellar feedback with individual stars. At high resolution, each star can be represented by its own particle ("star-by-star"). At coarser resolution, star particles represent specific realisations of stellar populations sampled from the IMF. Both methods share a unified implementation of stellar feedback tied to the individually tracked stars, including supernovae, stellar winds and radiation. Imladris has been optimised for both computational efficiency and memory footprint. We demonstrate the model with idealised galaxy simulations ($M_\mathrm{vir}\sim10^{10}-10^{11}\,\mathrm{M_\odot}$) spanning a baryonic mass resolution range of $2.5-1000\,\mathrm{M_\odot}$. Without re-calibration, the time-averaged star formation rate (SFR), galactic wind mass and energy loadings close to the disc are converged up to a resolution of $20\,\mathrm{M_\odot}$ within a factor of 1.1, 1.1 and 1.3, respectively, and 1.4, 1.6 and 2.5 up to $100\,\mathrm{M_\odot}$. Above this, SFRs become more bursty, while loading factors increase substantially. This is linked to resolution-dependent supernova clustering, which represents a fundamental barrier to convergence for any scheme attempting to model a self-consistent stellar feedback-regulated interstellar medium. Regardless, the ability to deploy the scheme across a wide range of resolutions (and to carry out in-depth resolution convergence studies) makes Imladris a powerful tool for numerical investigations of galaxy formation.

Since their discovery, AGN light curves are known to be intrinsically variable. In the optical/UV band, this variability is consistent with correlated or red noise and is particularly well described by the damped random walk (DRW) model. In this work, we evaluate the feasibility of a new method for identifying spatially unresolved couples of AGN through a fully Bayesian time-domain analysis of the observed light curves (LCs). More specifically, we check whether observed LCs are better described by a single DRW, which we interpret as emitted by a single massive black hole (MBH), or a pair of independent DRWs, generated by a pair of MBHs. We test the method on mock LCs associated with a single MBH and pairs generated with different cadences and lengths of observational campaigns. We constrained the occurrence of false positives, that is, the percentage of single MBH LCs that show substantial evidence in favour of the unresolved MBH pair scenario, finding a fraction of 0.2% and 0.59% in the even and uneven sampling scenarios. We discuss how well the method recovers the model parameters, showing that about 51% and 7% of the simulated LCs have all the recovered parameters within 20% of their true values in our best scenario of evenly sampled LCs for the single MBH and MBH pair scenarios, respectively. We finally study the region of the parameter space in which the detection of an MBH pair is possible, finding that such objects can be correctly identified if the timescales of the process describing the noise are very different, with a ratio smaller than ~0.2, and the variability amplitudes are similar, with their ratio bigger than ~0.2. When limiting to such a region of the parameter space, the fraction of pairs with all the recovered parameters within 20% of the injected values increases up to about 14% and 8% for evenly and unevenly sampled LCs, respectively.

Galaxy scaling relations encode key information about the structural, dynamical, and mass assembly histories of galaxies, and provide constraints on galaxy formation models as well as the onset of galaxy assembly. While these relations are well characterized out to intermediate redshifts, their existence during the first billion years of cosmic history remains largely unconstrained due to observational limitations. In this work, we investigate the Kormendy relation (KR) for spheroidal systems at $z~\ge~6$ using rest-frame $B$-band structural parameters derived from publicly available deep \textit{JWST} imaging of the GOODS, CEERS, PRIMER-UDS, and PRIMER-COSMOS fields. We find that spheroidal galaxies at these epochs already occupy a well-defined locus in the mean effective surface brightness $(\langle~\mu_{\rm e}~\rangle)$ and effective radius ($\rm~R_{\rm e}$) plane, demonstrating that a KR is already in place when the universe was less a gigayear old. The best-fit relation has a slope of $\beta~=~4.25^{+0.40}_{-0.39}$ and a zero-point of $\alpha~=~15.89^{+0.17}_{-0.17}$, indicating a steeper relation and systematically higher surface brightness compared to the local relation. This steepness reflects the compact sizes and high central stellar-mass densities of these systems, consistent with rapid, dissipative assembly in environments with high gas fractions, likely driven by efficient gas inflows, and gas-rich mergers. The presence of dense bulges embedded in some of these galaxies at similar redshifts further supports a common formation pathway for both bulges and spheroids. Altogether, these findings indicate a predominantly dissipative mode of assembly for the first spheroidal systems which may evolve into the compact quiescent galaxies observed at later cosmic epochs.

The spin-flip 21-cm signal from the Cosmic Dawn and the Epoch of Reionization is an essential probe of the conditions that led to the formation of the first luminous objects in the early Universe. However, its detection remains a major challenge owing to its low strength compared to the bright foregrounds and the requirement of precise calibration of the instrument to prevent systematics that could hinder a detection or lead to false inferences. REACH (Radio Experiment for the Analysis of Cosmic Hydrogen) is a radiometer experiment designed to detect this sky-averaged signal in the frequency range of 50--130~MHz. Using a wide-beam antenna, REACH calibration relies on internal reference sources, covering a broad range of temperatures and reflection coefficients. The choice of type and number of calibrators used significantly influences the quality of the calibration. This work investigates these effects and introduces a novel method for selecting an optimal set of calibration sources. With an optimised set, we aim to reduce calibration time, thereby increasing sky integration time while preserving calibration accuracy. We explore two optimisation strategies: one applied across the full receiver band and another performed on a frequency-by-frequency basis. Finally, we demonstrate that, with a total calibration time comparable to the conventional full-calibrator set, an optimised set with fewer calibrators achieves approximately a $15~\%$ reduction in calibrated temperature noise and improved absolute calibration of the instrument. This has implications for better calibration strategies in similar radiometer experiments.

Mirror Stars are a generic prediction of dissipative dark matter models, including minimal atomic dark matter and twin baryons in the Mirror Twin Higgs. Mirror Stars capture regular atoms from the interstellar medium through highly suppressed kinetic mixing interactions between the regular and the dark photon. This results in the accumulation of a "nugget", which draws heat from the mirror star core and emits distinctive X-ray and optical signals. In this work, we solve the stellar structure equations of optically thick nuggets across a wide range of the effective mirror star parameter space, and characterize their emission spectra using stellar atmosphere models. This complements an earlier analysis of lower-mass optically thin nuggets. We find that optically thick mirror star nuggets occupy distinct regions of the (stellar surface temperature, luminosity, surface gravity) space, and can be distinguished from regular stars in both HR diagrams and temperature-surface-gravity diagrams using astrometric and spectroscopic stellar catalogues. Our detailed predictions, which are publicly available, now give for the first time a general picture of mirror star signals in the optical and IR to enable realistic mirror star searches using existing catalogues and new telescope observations.

We analyze a suite of high-resolution cosmological zoom-in simulations of jetted Seyfert galaxies over $z\leq10$ projected on the major scaling relations, comparing trajectories of `normal' versus jet-hosting galaxies. Models include thermal and mechanical jet feedback launched from supermassive black holes (SMBHs) seeded at $z\sim9.1$ and $z\sim3.7$ with $M_\bullet\sim10^6\,M_\odot$ in galaxies within dark matter halos of ${\rm log}\,M_{\rm halo}/M_\odot\sim11.8$ at $z=0$. A single parameter, the SMBH accretion efficiency, has been varied resulting in $L_{\rm jet}\sim10^{40-42}\,{\rm erg\,s^{-1}}$, and SMBH accretion rates range between $\sim 0.2-10^{-4}$ of the Eddington rate. We find that jet feedback (1) suppresses central star formation rates (SFRs), redistributes gas to larger radii, (2) generates long-lived expanding shocks that couple to the ISM and CGM, (3) reduces stellar mass ($M_*$), shifting galaxies toward lower central concentrations, and (4) alters host trajectories on the $M_{\rm halo}-M_*$, specific SFR$-M_*$, $M_\bullet-\sigma_{\rm bulge}$, Mass$-$Metallicity, Kennicutt-Schmidt, and baryonic Tully-Fisher relation planes. Specifically, we find that jetted Seyferts live longer in the green valley and more frequently move to the quenched region in comparison to the non-jetted galaxies. Despite producing only transient quenching, Seyfert jets cause persistent structural, kinematic and chemical signatures, including flatter rotation curves, elevated CGM metallicities, and reduced cold gas clumping. (5) Early SMBH seeding and stronger jets amplify these effects, yielding galaxies that lie systematically closer to some of the empirical relations, e.g., $M_{\rm halo}-M_*$, while showing offsets for others, e.g., Kennicutt-Schmidt, and demonstrating that low-luminosity Seyfert jets can exert a significant long-term influence on galaxy evolution.

A recent preprint by Sugiyama et al. reported the discovery of twelve candidates for short-timescale (less than one day) gravitational microlensing events based on high-cadence photometric observations of the Andromeda Galaxy (M31) using the Subaru Hyper Suprime-Cam. These detections were attributed to a large population of planetary-mass primordial black holes (PBHs) that could account for the entirety of the dark matter in the Milky Way and M31 halos. However, these results are in clear tension with previous searches for short-timescale microlensing events toward the Magellanic Clouds, such as those by the OGLE survey. In addition, both the temporal and spatial distributions of the Subaru candidates are inconsistent with expectations for microlensing events. Here, we reanalyze the Subaru data using an independent difference image analysis photometric pipeline. We find that all twelve candidates identified by Sugiyama et al. exhibit asymmetric light curves and/or variability on multiple nights of Subaru observations. Our analysis reveals that among them ten objects are RR Lyrae stars, one is an eclipsing binary, and one is an unclassified variable star. We find no compelling evidence for short-timescale microlensing events among the candidates identified in the Subaru data set, nor for a significant population of planetary-mass PBHs as dark matter components. Our results underscore the necessity of robust variable-star rejection in high-cadence microlensing searches using large telescopes.

Context. Stellar feedback regulates star formation and shapes the interstellar medium, yet its role during the collapse of molecular clouds remains uncertain over a wide range of initial conditions. Aims. We explore how stellar winds and supernovae influence star formation in collapsing gas clouds that span a broad parameter space in mass, size, and metallicity. Methods. Using a one-dimensional numerical model, we follow the evolution of feedback-driven bubbles produced by embedded clusters, incorporating time-dependent energy and mass injection, self-gravity, integrated cloud collapse, radiative cooling, shell instabilities, and triggered star formation. Our treatment of gas cooling in the hot bubble explicitly accounts for heat transfer across the bubble-shell interface. Results. We find that metallicity acts as a key regulator of feedback, comparable in importance to cloud mass and radius. In low-metallicity clouds, reduced radiative cooling is offset by weaker stellar winds, leading to prolonged star formation and higher efficiencies. Across a substantial portion of parameter space, the expanding shell undergoes a stalling phase that further enhances the star formation efficiency, an outcome that is not observed at higher metallicities. Conclusions. Our results suggest that the diverse properties of star clusters across cosmic time may arise from the metallicity-dependent interplay between stellar feedback and gas cooling.

Despite their ubiquity in the astronomical literature, there is no consensus tier list of the genitive forms of the 88 constellations officially recognized by the International Astronomical Union. To address this pressing open question, I conduct an anonymous pair comparison survey of 74 professional astronomers to rank these constellation genitives on their aesthetic merit. After each survey response, I use active sampling to select a new set of pair comparisons that maximizes expected information gain, and update overall scores based on a fully Bayesian framework. I find that Pegasi is the most aesthetically pleasing constellation genitive overall, narrowly edging out Centauri and Andromedae. While most astronomers self-report Orionis to be their top choice before taking the survey, this well-recognized constellation genitive only places seventh in the final ranking. Gruis, meanwhile, receives the dubious honor of last place. When breaking down the ranking by career stage, I find tentative evidence for generational differences in aesthetic taste. A larger sample of faculty members is needed to confirm this result. Finally, I offer unsolicited commentary on the phonetic appeal and cultural significance of the genitives ranked in the top and bottom five.

Interstellar dust forms during stellar mass-loss events, occurring either during a star's giant phase or during supernova explosions. This PhD thesis provides an in-depth investigation into the theory of dust condensation and growth, specifically applied to the winds of cool giants such as Asymptotic Giant Branch (AGB) stars. The thesis begins with a theoretical description of the chemical reactions that initiate seed formation within a cooling flow. It then details an efficient mechanism - a moment method based on size-weighted moments of the grain size distribution - to compute dust evolution during growth. This theoretical framework is applied to dust-driven winds from carbon-rich AGB stars. By deriving wind equations and self-consistently incorporating dust formation, the research demonstrates that radiation pressure on dust forming in the expanding atmosphere can drive a stellar wind. Furthermore, a parameter study covering the giant region of the Hertzsprung-Russell (HR) diagram is used to derive mass-loss formulas for these winds. The final chapter expands the dust formation theory to investigate the condensation of heterogeneous grains.

The absence of helium features in optical spectra is one of the classification criteria for Type Ic supernovae (SNe Ic). However, it is highly debated whether helium is truly absent in ejecta or spectroscopically undetectable in the optical region. The near-infrared (NIR) region contains cleaner He lines that are less blended with other common ions in SNe Ic ejecta. We perform full spectral modeling on the near-peak-light optical and NIR spectra of the SN Ic 2014L to quantitatively constrain helium and other outer-ejecta properties, using the radiative transfer code TARDIS. We employ a deep-learning emulator for SNe Ic spectra that serves as a fast surrogate for TARDIS simulations. We then integrate the emulator within the Bayesian inference framework to infer the ejecta properties. The emulator achieves a mean fractional error of 1% between the emulated and TARDIS fluxes across all wavelengths and all samples in the test dataset. We constrain 0.018 to 0.020 M_sun (16% to 84% posterior percentile) of He above the photosphere near peak light in SN 2014L, inferred from the observed spectra covering 3500A to 24000A. A Bayesian statistical test shows that the observed spectra are inconsistent with no helium. Furthermore, the posterior favors a power-law density exponent of -7.04 to -6.88 (16% to 84% credible interval), consistent with theoretical calculations of radiation-dominated explosions. This work demonstrates that Bayesian radiative-transfer inference over a wide wavelength range provides a powerful path toward systematic constraints on He in SNe Ic.

Close-in terrestrial exoplanets around M dwarfs reside in dense, magnetized winds, where non-ideal plasma coupling can strongly affect how electromagnetic energy is redistributed within the dayside interaction region. We present three-dimensional resistive magnetohydrodynamic simulations of the TRAPPIST-1 wind interacting with a dipolar TRAPPIST-1e magnetosphere for three stellar-wind forcing cases and four prescribed magnetic diffusivities, $\eta=(0,\ 538.018,\ 5.38018\times10^{8},\ 5.38018\times10^{12})$ cm$^{2}$ s$^{-1}$. Energy transport is diagnosed using maps of the total energy density, the magnitude of the total Poynting flux, and the divergence of the total Poynting flux. We further estimate a radio-power proxy from the volume integral of $\nabla\cdot \mathbf{S}_{\rm total}$ over the dayside bow-shock and magnetopause layers. Across all cases, increasing prescribed $\eta$ broadens the coupling layer and shifts the dominant energy-conversion regions from thin, patchy boundary arcs to thicker, more spatially extended structures, with an increasing relative contribution from the magnetopause. The inferred radio-power proxy increases by several orders of magnitude across the explored scan. However, because the estimated numerical magnetic diffusivity in the strongest-gradient regions is $\eta_{\rm num}\sim10^{15}$-$10^{16}$ cm$^{2}$ s$^{-1}$, the present $\eta$ scan is best interpreted as a controlled sensitivity study rather than as a direct constraint on the physical diffusivity of the TRAPPIST-1e environment. For the adopted planetary fields ($B_{\rm eq}=0.32$-$1.28$ G), the maximum cyclotron frequencies are $\nu_{c,\max}\approx1.8$-$7.2$ MHz, below the ground-based window, implying that meaningful radio constraints on TRAPPIST-1e magnetism will require space-based observations below 10 MHz or substantially stronger planetary fields than those assumed here.

We present a suite of radiation-magnetohydrodynamics simulations from the POPSICLE project that follow the long-term growth (~50 kyr) of primordial protostars while self-consistently coupling radiation, turbulence, and magnetic fields. The simulation suite is designed to quantify the relative impacts of the pathways of radiative feedback in Pop III stars - the extreme-ultraviolet (EUV) ionization and Lyman-Werner (LW) dissociation - by considering simulations with and without their inclusion. We find that without HI shielding, LW feedback alone can suppress and ultimately terminate accretion. With HI shielding, the large column densities near the protostar significantly weaken LW feedback. In the polar direction, atomic hydrogen fully shields LW radiation where $H_2$ self-shielding alone is insufficient. This leads to lower gas temperatures near the protostar and higher accretion rates, yielding larger final stellar masses than in models without shielding. The HII regions remain compact and confined to less than about 100 AU measured outward from the sink accretion radius (75 AU) due to high gas densities and continuous gas replenishment that inhibit the thermal pressure-driven breakout of the ionization front even for high ionizing luminosities. These results demonstrate that the interplay of gas dynamics, shielding, and radiative feedback can significantly alter the growth of Pop III stars. We discuss the implications for the initial mass function of primordial stars and the influence of feedback from early stellar populations.

We present predictions for solar system objects the Vera C.\ Rubin Observatory Legacy Survey of Space and Time (LSST) will not detect over its ten-year baseline survey. Employing state-of-the-art synthetic population models and the \texttt{Sorcha} survey simulator, we identify non-yield populations spanning geometric, photometric, kinematic, temporal, and computational failure modes. Notable subpopulations include objects whose peak brightness coincides exclusively with scheduled telescope downtime, objects whose detections fall within Rubin focal plane chip gaps, and objects whose orbital arcs expire before linking jobs are dispatched from the compute queue. We additionally characterise the non-yield arising from the Death Star (DS-1; $D \approx 160$~km), whose orbital mechanics (when constrained by the well-established Endor engagement geometry \citep{lucas83}) place it at a maximum heliocentric distance of $27.5$~au and an apparent magnitude of $m_r \approx 19$-23, squarely within the LSST operational photometric window. Its absence from the LSST alert stream is interpreted as confirmation of its destruction at the Battle of Endor. The failure to detect the Sun within the LSST should be a stark warning to the community of the LSST's inability to catalogue the solar system (by mass).

In this paper, we investigate the robustness of WISE mid-IR color selection (W1-W2) for identifying obscured (Type 2) active galactic nuclei (AGNs) at low redshift (z<0.3), using a sample of ~360,000 SDSS galaxies classified via emission lines into Seyfert 2 (Sy2), LINER, and star-forming (BPT-SF) galaxies. We find that the K-correction is essential to remove non-AGN contamination, and once applied the simple W1-W2>0.5 selection emerges as optimal in terms of purity and completeness of AGN selection. However, we confirm that even this lenient cut selects only ~13% of Sy2 galaxies and that achieving W1-W2>0.5 requires AGN contributing >75% of the total infrared luminosity, which is uncommon. Although mid-IR-selected Sy2s tend to be luminous, the high [OIII] luminosity does not guarantee red W1-W2 (nor does any other tested global or NLR-scale parameter), suggesting the critical role of obscuration on smaller scales. <1% of BPT-SF systems (but making ~20% of all mid-IR selected galaxies) exhibit W1-W2>0.5 colors. Such colors cannot be reproduced by models of star-heated dust alone. Red BPT-SFs tend to have higher W4 luminosities than expected from SF, indicating true AGNs. Intriguingly, mid-IR AGNs in massive bulges ($M_{\mathrm{bulge}} \gtrsim 10^{10} M_{\odot}$) predominantly (84%) manifest themselves as BPT-AGNs, whereas those in low-mass bulges ($\lesssim 10^{10} M_{\odot}$) mostly (60%) manifest as BPT-SF. This BPT-AGN vs.\ BPT-SF dichotomy does not extend to total stellar mass. We conclude that although the mid-IR AGN selection is incomplete, its strength lies in identifying optically inconspicuous AGNs with low-mass bulges, regardless of the total mass.

Accurately modeling the inspiral-merger-ringdown (IMR) signal of coalescing compact objects is essential for the test of general relativity. However, it is known that astrophysical environments can distort gravitational-wave (GW) signal and, if ignored, may bias parameter estimation or even our understanding of gravity. Previous studies suggest that various astrophysical environmental effects can be modeled in a unified way by introducing an effective acceleration. However, such models are based on stationary phase approximation (SPA) and post-Newtonian (PN) formalism, which are inconsistent with the fast orbital evolution and strong gravity in the final merger-ringdown phase. To overcome this limit, we introduce frequency-domain spectral differentiation (FSD), which maps the time shift of the signal caused by acceleration into a differentiation in the frequency domain. The mapping does not rely on SPA or PN formalism, therefore can be used to construct the accelerated waveform across the entire IMR phases. We compare the FSD waveforms with the conventional SPA+PN ones, and find that the former more faithfully match the simulated signals of accelerating sources, especially in the merger-ringdown phase and when higher-order FSD corrections are included. A Fisher information matrix analysis suggests that FSD waveforms can achieve higher precision than SPA+PN waveforms in measuring effective acceleration. Therefore, the FSD method offers a more self-consistent treatment of various astrophysical environmental effects in the final merger-ringdown phase of binary GW sources.

In the late 1990s, the Arecibo Observatory and its planetary radar system were upgraded to increase sensitivity by a factor of 20. This upgrade substantially improved the quality of the data and the ability to observe terrestrial planets, outer planet satellites, planetary rings, and near-Earth objects until the telescope's collapse in 2020. The higher sensitivity allowed radar observations of 889 near-Earth asteroids and comets from 1997 to 2020, compared to the 40 achieved in the previous 30 years, and showed that the population of near-Earth asteroids is heterogeneous, suggesting a wide variety of formation and evolution mechanisms. The planetary radar's ability to see through the atmospheres of Venus and Titan, into the shadows of Mercury and the Moon, and under the surface of the Moon and Mars provided a unique perspective on those bodies that has driven in-situ exploration. No other existing or planned facility matches the sensitivity that Arecibo had.

We report a large misalignment between the continuous jet and the discrete ejecta in GRS 1915+105, detected in April 2023 with the East Asian VLBI network (EAVN). Two-sided ejecta are shown at 6.7 GHz images and central continuous jets are resolved at 43 GHz by EAVN quasi-simultaneously. While the continuous jet was aligned with the long-standing jet position angle (PA) of about 147 degree, the discrete ejecta appeared at a markedly different PA about 188 degree, with the lowest intrinsic velocity about 0.35 c ever reported. A similar misalignment of PA between discrete ejecta and continuous jet was independently detected in late September of 2023 during a consecutive flare event. The pronounced and recurrent angular deviations suggest a time-variable jet launching geometry, which, in conjunction with the observed X-ray obscuration, can be attributable to a warped accretion disk. Our result could offer new insight into the fundamental differences between continuous jet and discrete ejecta, and broadly provides a clue to understand the phenomena for transient black hole X-Ray binaries and changing-look active galactic nuclei during the X-ray obscured phase.

Wide-field optical imaging surveys are efficient at identifying galaxy clusters, but optically identified clusters suffer from projection effects--physically unassociated galaxies along the line of sight can be misidentified as cluster members due to distance uncertainties. Previous studies have used spectroscopic follow-up observations of cluster members to quantify projection effects; however, such follow-up efforts cannot keep pace with the rapidly growing cluster samples. On the other hand, spectroscopic surveys designed for large-scale structure studies collect tens of millions of spectra but tend to have sparse spectra in cluster regions. To bridge this gap, we develop a clustering redshift approach that cross-correlates cluster members with sparse, non-cluster-targeted spectroscopic galaxy samples. We validate this approach using the Cardinal simulation, recovering the correct spectroscopic distribution and projection effect parameters of redMaPPer cluster members. Our approach is insensitive to the selection of the spectroscopic sample and paves the way for calibrating the upcoming LSST clusters using DESI and Roman spectroscopic samples.

We propose a new mechanism for generating a primordial electromagnetic relic during the recombination--decoupling transition, based on the rate-dependent thermodynamics of the cosmic photon gas. Treating the photon sector as an open system coupled to the electron plasma, we show that a finite Thomson relaxation rate generates a departure from instantaneous thermal equilibrium, leading to non-adiabatic mode squeezing. As this relaxation rate rapidly decreases across recombination, the system quickly loses the ability to further amplify the deviation, and the squeezing freezes out at a small but finite value. This dynamics is naturally described as a narrow transition layer between an adiabatic tracking regime and a post-relaxation freeze-out regime. By a canonical transformation, the reduced evolution equation is recast into a forced oscillator with a smooth effective potential, clarifying the origin of the squeezing and the selection of the relic scale. Projecting the resulting non-equilibrium electromagnetic relic onto the magnetic sector, we derive the corresponding spectrum and show that its characteristic peak is controlled not by the squeezing parameter alone but by the weighted combination \(k^3\mathscr S_k\). In representative realizations, the peak corresponds today to scales of order \(10\)--\(20\) Mpc, while the present-day field amplitude remains extremely small. The mechanism is therefore better viewed as a source of a frozen non-equilibrium electromagnetic relic than as a complete explanation of the observed cosmic magnetic fields.

M-dwarf flare stars like AD Leo are laboratories for studying intense magnetic activities. The coherent radio bursts they produce are powerful probes of stellar coronal plasma and magnetic fields. In this study, we present high-resolution observations of AD Leo from the Five-hundred-meter Aperture Spherical radio Telescope (FAST) that reveal wave-like structures in its radio dynamic spectrum. The observations show trains of short-duration, narrowband sub-bursts where the central frequency, frequency drift rate, and flux density are all simultaneously modulated with a period of 1.53 s. Notably, modulation of the central frequency is approximately in-phase with that of the drift rate but roughly in anti-phase with that of the flux density. Furthermore, the amplitude of the frequency modulation grows with an e-fold timescale of 2.4 s. We interpret the observed sinusoidal frequency modulations as a possible signature of a magnetohydrodynamic (MHD) wave in the stellar corona. Our work provides a window into stellar coronal seismology and offers an opportunity to infer the local plasma environment via the MHD wave model.

We present a multi-epoch study of the extreme X-ray variability of the type~1 quasar SDSS~J000532.84+200717.4 using archival observations from \textit{XMM-Newton}, \textit{Swift}/XRT, \textit{EP-FXT}, and \textit{ROSAT}, together with new optical spectroscopy and multi-wavelength photometry. The 0.2--10~keV X-ray flux exhibits a transition from a high state to a subsequent low state, declining by more than an order of magnitude and placing the source in the X-ray--weak regime ($\Delta\alpha_{\rm ox} \lesssim -0.3$). Significant variability on timescales of days to weeks persists within the low state. In contrast, the optical and mid-infrared emission remain stable over decade-long timescales, while the UV continuum varies only mildly and broadly tracks the X-ray evolution. Multi-epoch optical spectroscopy shows no significant long-term changes in either the continuum shape or the broad emission-line profiles. The \ion{Mg}{2} emission is relatively weak compared with typical quasars, suggesting similarities to weak-line quasars. The pronounced wavelength-dependent variability indicates that the accretion disk remains largely intact while the X-ray emission undergoes dramatic changes. The spectral hardening in the low state and the viability of ionized partial-covering models are consistent with variable, largely dust-free absorbing gas, possibly associated with clumpy inner disk winds, although intrinsic coronal variations cannot be excluded. SDSS~J0005+200717.4 therefore provides evidence that extreme X-ray weakness can arise as a transient phase in otherwise normal quasars.

TESS (Transiting Exoplanet Survey Satellite) has produced long-term photometry for millions of stars across the sky. In this work, we present an asteroseismic catalogue of 19,151 red giants in the TESS Continuous Viewing Zones using sectors 1--87 (Years 1--7). We visually assessed the power spectra for oscillations, and then applied the computationally efficient nuSYD method to confirm reliability. We identified an increase of 80% in the number of previously known oscillating red giants at a TESS magnitude $>$ 8. We determined the frequency of maximum power ($\rm \nu_{max}$) and the large frequency separation ($\rm \Delta \nu$) using the pySYD pipeline, achieving typical precisions of 1.5% and 1%, respectively. We classified the stars into Red Giant Branch (RGB) and Core Helium Burning (CHeB) classes using a Convolutional Neural Network. Using spectroscopic data for 10,298 stars with reliable asteroseismic measurements, we have been able to measure stellar mass and radii with precisions of 7.5% and 2.8%, which is comparable to that from 4-yr $Kepler$ data. A comparison of the seismic radii with Gaia radii shows excellent agreement. With three years of TESS data, the asteroseismic parameters are precise enough to identify the RGB bump and delineate the Zero Age Helium Burning edge. Combined with astrometric data, these parameters reveal established trends across the Galactic plane, providing a valuable set of uniformly determined asteroseismic parameters for Galactic Archaeology.

Convection and rotation are both key processes in stellar evolution modelling. While standard mixing-length theory (MLT) provides a widely used modelling of convection, it neglects the effects of rotation on convective transport. We investigate how rotating mixing-length theory (R-MLT), which accounts for the influence of rotation on convection, affects the internal structure, convective mixing, and angular momentum transport in stellar models in comparison to the standard non-rotating MLT. Using the MESA stellar structure and evolution software, we model the main-sequence evolution of a 5 M$_{\odot}$ star, for three cases: non-rotating, rotating with standard MLT for modelling convection, and rotating with R-MLT in convection zones, with the initial rotation rate set to 20 percent of the critical (Keplerian) value at the surface for the rotating models. We find that R-MLT reduces both the convective velocity and mixing length in the stellar core, leading to a smaller convective diffusion coefficient and about 20 percent reduction in the extent of the convective overshooting region. While the overall size of the convective core remains nearly unchanged, R-MLT changes the resulting chemical gradient at the core-envelope boundary, shifting the peak of the Brunt-Väisälä frequency and modifying the angular momentum transport in that region. Including the effects of rotation in the treatment of convection through R-MLT introduces measurable structural and transport differences, underscoring the importance of incorporating rotation-convection coupling in models of stars.

Tidally locked lava planets are hot, rocky worlds on close-in orbits with a permanent molten dayside. With JWST, their surfaces and atmospheres are beginning to be revealed. This work investigates 3D magma-ocean dynamics, derives scaling laws for the resulting ocean heat transport (OHT), and predicts its detectability. For the first time, the ocean circulation driven by the intense momentum and mass exchanges with the supersonic atmosphere is considered in addition to that by thermal forcing. The wind forcing turns out to overwhelmingly dominate the other two mechanisms, driving ocean currents reaching $\sim$100 m s$^{-1}$ and greatly expanding the latitudinal extent of the Matsuno-Gill response. Despite these extreme flow speeds, scaling analysis and 3D simulations consistently demonstrate that magma-ocean circulation alone does not produce an observable hotspot offset. This inefficiency arises because basin geometry and circulation structure fundamentally constrain zonal heat redistribution, suppressing large-scale longitudinal transport even under vigorous flow.

Marked correlation functions, in which galaxy properties such as luminosity or stellar mass are treated as marks, are widely used to test models of galaxy formation. In astronomy, however, these statistics are typically implemented as summary measures that do not preserve the joint structure of mark pairs conditioned on separation. In this work, we formulate galaxies as points $(x,m)$ on the product space $\mathbb{R}^3\times\mathcal{M}$, where $x$ denotes position and $m$ a mark, and introduce the joint pair correlation function $g(r;m_1,m_2)$ as the fundamental quantity describing mark-dependent clustering. We further define a diagnostic quantity $\Delta_{\mathrm{ind}}(r;m_1,m_2)$ that locally quantifies deviations from the independence hypothesis relative to spatial clustering alone, thereby providing a projection-free description of which mark pairs are over- or underrepresented at a given separation scale. Within this framework, commonly used diagnostics such as the inhomogeneous cross-$J$ function are naturally interpreted as summary statistics obtained through averaging over mark sets and geometric-event-based reductions of the joint structure. This perspective clarifies that previously discussed marked effects, including assembly bias, correspond to projections of an underlying joint dependence, and that observationally accessible information is the existence of non-factorizable joint structure itself. The present formulation provides both a fundamental quantity and practical diagnostics for its characterization.

We report the detection of a gamma-ray spectral line at approximately 1.5 GeV in three active galactic nuclei (AGN) using 17 years of Fermi-LAT observations. The sample includes both blazars (with relativistic jets directed toward Earth) and a radio galaxy (with a misaligned jet, free from significant beaming effects). The line is detected with local significances of $\sim$4.1$\sigma$, $\sim$3.9$\sigma$, and $\sim$2.8$\sigma$ in the individual sources. A joint likelihood analysis yields a combined test statistic TS $\simeq$ 57.77, corresponding to a significance well above 5$\sigma$. The line flux remains stable over the full observation period, in contrast to the variable continuum emission from the AGN. The appearance of an identical spectral feature in astrophysically distinct environments is difficult to reconcile with standard jet-based emission mechanisms. While a conventional astrophysical explanation remains elusive, the signal's characteristics are consistent with predictions for dark matter annihilation. This finding motivates further investigation into the nature of this spectral feature and its possible connection to particle dark matter.

We construct a geometric framework for cosmological large-scale structure based on optimal transport theory and Wasserstein geometry. In this framework, Ricci curvature on the probability measure space $\mathcal{P}_2(M)$ is characterized by the geodesic convexity of entropy and is formulated as the response of probability distributions to optimal transport. We introduce effective Ricci curvatures $K_{\mathrm{eff}}^{(\infty)}$ and $K_{\mathrm{eff}}^{(N)}$ associated with Kullback--Leibler-type and Rényi-type entropies, corresponding respectively to the curvature-dimension conditions CD$(K,\infty)$ and CD$(K,N)$. By localizing these curvatures to finite scales using local and reference measures, we construct curvature indicators applicable to observational data. Under a local quadratic approximation, the effective curvature reduces to the Hessian of the log-density, showing that conventional Hessian-based structure classifications arise as a limiting case of the present framework. We further show that effective curvature depends on observational scale and formulate this dependence as a scale flow, distinct from Ricci flow because it describes a change of resolution rather than a time evolution of geometry. Treating curvature as a random field then extends the statistical description of density fields: curvature statistics are given by higher-order weighted integrals of the power spectrum and by spatial derivatives of the correlation function, emphasizing geometric rather than amplitude information. This framework provides a unified connection between optimal transport geometry and cosmological structure analysis, and offers a new perspective on multiscale structure and nonlinear statistics.

Recent observations have confirmed the existence of rings around minor bodies in the outer Solar System. These objects may possess satellites as well. Here we analytically investigate the interaction between such rings and satellites. We show that the perturbations from the moons may efficiently lead to off-equatorial rings around minor bodies like trans-neptunian objects or centaurs. In particular, we derive criteria for the orbital elements under which such misaligned rings may exist. These considerations will be easily testable with the upcoming deep sky surveys.

With their emission-line dominated spectra, the appearance of Wolf-Rayet stars is shaped by their strong stellar winds. Yet, the physical mechanisms behind their high mass loss have long remained enigmatic. While we know nowadays that radiative driving is sufficient to explain WR-type outflows, a coherent description of them is still lacking, not least to the complex physical conditions invalidating some of the approximations sufficient for other hot-star winds. One promising instrument towards a better understanding of WR winds are comoving-frame, non-LTE stellar atmosphere models including a consistent solution of the hydrodynamics. While so far limited to 1D, their detailed treatment of the radiative transfer and the population numbers is key to overcome the traditional problem of connecting stellar structure models with observed spectra. By creating larger model sequences, we can identify previously unknown scalings and describe trends of WR wind quantities with fundamental stellar parameters and abundances. This article will present a summary of recent insights on WR-type winds, revealing a complex picture with various remaining challenges. Beside covering classical, hydrogen-free WR stars, we present new results to uncover dependencies of later-type WR stars and the presence of hydrogen-containing envelopes. We further discuss oncoming challenges and insights from 2D and 3D RHD simulations which need to be mapped into 1D dynamical atmosphere models.

Large-amplitude prominence oscillations offer diagnostic information relevant to understanding the magnetic and plasma structure of solar prominences. Accurate prominence seismology requires the use of reliable models. The so-called pendulum model for large-amplitude longitudinal prominence oscillations has demonstrated robustness against observations and numerical simulations. Recent improvements have extended the model to situations with non-uniform gravity, thus leading to corrections that have implications for the inference of the magnetic field strength. In this study we quantify how the different model predictions given by the original and extended pendulum models impact the inference of the minimum magnetic field strength derived from the observed periods of large-amplitude longitudinal prominence oscillations. The analysis we conducted follows a Bayesian approach to solve the inference problem and assess the absolute and relative plausibilities of the two considered models in explaining the observed data, with their uncertainty. We find that the Bayesian solution to the inference problem provides well-constrained posteriors for the minimum magnetic field strength. However, the solutions from each adopted model differ, with differences increasing with the oscillation period. A model comparison analysis results in the extended model being more plausible in the full range of observed periods. However, the magnitude of the Bayes factor is not large enough to determine whether there is positive evidence supporting any of the models. We suggest computing model-averaged posteriors as the most reasonable solution to the inference problem.

The advent of large-scale surveys requires efficient ML techniques to exploit the information of massive datasets. We present OJALA, a transformer-based autoregressive foundation model designed to simultaneously classify astronomical objects and infer their physical parameters using 54 narrow bands from J-PAS, combined with broad bands from the DESI Legacy Imaging Surveys and WISE. The model is trained on $\sim20$ million synthetic SEDs generated from DESI DR1 spectra. We validate OJALA using a cross-matched sample of $\sim121,000$ objects between J-PAS and DESI. The model achieves a weighted F1-score of approximately 0.9 for spectral classification (stars, galaxies, and QSOs) at $i < 21$. For galaxies, we recover photo-z with a precision of $\sigma_{\rm NMAD} < 0.01$, while for QSOs, the precision improves significantly at $z > 1.5$, reaching $\sigma_{\rm NMAD} \approx 0.006$ at $z \approx 3.5$. We demonstrate robust estimation of physical properties for galaxies, recovering stellar masses and SFR with a scatter of approximately 0.11 dex and 0.22 dex, respectively. Furthermore, the model accurately predicts EWs for major optical emission lines, allowing for the derivation of extinction-corrected H$\alpha$ luminosities with a scatter of 0.29 dex. OJALA successfully reproduces the BPT and WHAN diagnostic diagrams, classifying SF, AGN, and passive galaxies with F1-scores typically ranging from 70% to 90% depending on the diagnostic class. For stars, the model reliably infers effective temperature and metallicity, though surface gravity remains challenging. Finally, we show the modularity of the architecture by fine-tuning the pre-trained embeddings to predict BH masses, a property not included in the primary training, recovering spectroscopic virial estimates with a precision of approximately 0.5 dex. We release the code, model weights, and a comprehensive VAC for the J-PAS EDR.

We investigate the heteroclinic connections between stable and unstable manifolds of unstable periodic orbits associated with the most important mean motion resonances (MMRs) in the Sun-Jupiter planar restricted three-body problem. We explicitly compute the stable and unstable manifolds of the unstable periodic orbits associated with the first order interior MMRs 2:1, 3:2, and the exterior MMR 2:3. We also compute short-time FLI maps showing the chaotic saddle structure created by the manifolds of several interior or exterior MMRs other than the 1:1 (co-orbital) resonance. Transits of particles from the exterior to the interior of Jupiter's orbit and vice versa are allowed for Tisserand parameter lesser than 3, and are shown to exist through a variety of heteroclinic channels. Besides the classical ones by Koon et al., we find heteroclinic connections between manifolds of short-period orbits around L3 and periodic orbits of interior or exterior first order MMRs, as well as direct connections between interior and exterior MMR manifolds not involving co-orbital periodic orbits. Through these manifolds and the corresponding FLI ridges, we explain the 'arches-of-chaos' in the asteroid orbital plane (a,e). Chaotic orbits shadowing heteroclinic trajectories exhibit resonance hopping, suggesting links to quasi-Hildas and Jupiter-family comets. Results are obtained in the circular RTBP but persist in the elliptic problem.

How do Dwarf Galaxies differ from spirals? Does star formation produce radio and far-infrared emission in the same way as in spiral galaxies? Radio, FarIR, and CO emission depend on gas density, temperature, magnetic field strength, and metallicity. The radio-FarIR correlation and Schmidt-Kennicutt relation characterize the links for Milky Way-like galaxies but do they hold for smaller objects, with different morphologies? Here we extend our previous work on the IR, line, and radio emission of local and high-z galaxies to local star-forming low-mass and dwarf galaxies. The calculation of the cosmic ray (CR) densities were improved compared to the previous version of the model. The CR ionization rate we found for the different galaxy samples is higher by a factor of three than for the solar neighborhood. This means that the mean yield of low-energy CR particles three times higher in external galaxies than was observed by Voyager I. The dependence of the N_H2/I_CO factor on the metallicity and stellar mass are calculated by the model. The weaker CO emission from low-metallicity galaxies is due to the large amount of (CO-dark) H_2 surrounding the regions where CO is not photo-dissociated. Within our model framework, star-forming low-mass and dwarf galaxies follow the radio-IR correlation.

We examine the origin of the short-lived radionuclides (SLRs, defined as having half-lives between 0.1 and 100 Ma) present in the early Solar System (ESS) by investigating how predictions of their abundances in the interstellar medium (ISM) from steady-state equilibrium relate to their ESS values. For this, we take into account the non-negligible time $t_{\mathrm{iso}}$ elapsed between the isolation of the pre-solar molecular cloud and the formation of the ESS, during which the SLRs decayed freely. We also consider the alternative scenario in which the pre-solar molecular cloud remained partially mixed with the ISM, with a mixing timescale $t_{\mathrm{mix}}$. We find that the ESS abundances of $^{107}$Pd and $^{182}$Hf produced by \textit{slow} neutron captures (\textit{s}-process), and of $^{53}$Mn and $^{60}$Fe produced by explosive nucleosynthesis, can be consistently explained within these scenarios. Their required $t_{\mathrm{iso}}$ is 9-12 Ma, and their required $t_{\mathrm{mix}}$ is 11-14 Ma (with one potential exception of $t_{\mathrm{mix}}$ = 38 Ma), depending on galactic uncertainties, such as the galactic star formation history and efficiency and the star-to-gas mass ratio. Another \textit{s}-process SLR, $^{205}$Pb has a more uncertain ESS value, and falls within only some of these time values. The same applies to the SLRs produced by the $p$-process ($^{92}$Nb and $^{146}$Sm), depending on the latter's half-life. In agreement with previous studies, we find that the ESS abundances of the \textit{rapid} neutron-capture isotopes ($^{129}$I, $^{244}$Pu, and $^{247}$Cm) and of the most short-lived radionuclides ($^{26}$Al, $^{36}$Cl and $^{41}$Ca) cannot be explained by assuming steady-state equilibrium in the ISM.

We develop a geometric formulation of peak statistics in cosmological density fields based on optimal transport and entropy. In this framework, the density field is treated as a probability measure, and its local structure is characterized by the Hessian of the log-density, which arises as the local response of an entropy functional in Wasserstein space. Peaks are thereby defined as positive-curvature stationary points, and their number density is expressed as a curvature-conditioned point process. In the linear Gaussian limit, the joint distribution of local variables closes in terms of a finite set of spectral moments, recovering the standard theory of peak statistics, known as BBKS. This clarifies that BBKS corresponds to a solvable limit of a more general structure combining probability distributions, curvature constraints, and geometric measure. The framework extends naturally beyond Gaussianity and linearity. Deviations from Gaussianity are incorporated as deformations of the joint distribution of curvature variables, while nonlinear structures are described through the curvature of the log-density. We further derive the two- and three-point peak statistics as curvature-conditioned $n$-point measures, and show that the full hierarchy of peak statistics can be organized as response functions to long-wavelength background modes. In this formulation, the conventional peak bias appears as the lowest-order response coefficient, with higher-order correlations arising as its natural extensions. This work embeds peak theory into a unified geometric framework and provides a systematic basis for incorporating nonlinearity, non-Gaussianity, and higher-order statistics, with direct relevance for observational applications.

We present a comprehensive 20-year multiwavelength variability study of the blazar PKS 2155-304, one of the most luminous and extensively monitored high-frequency-peaked BL Lac objects in the southern hemisphere. Using Fermi-LAT $\gamma$-ray data together with Swift-XRT and UVOT observations spanning 2005-2024, we trace the long-term evolution of its flux, interband correlations, and spectral behaviour across the optical, X-ray, and $\gamma$-ray bands. All flux distributions are compatible with log-normality. Interestingly, the optical domain exhibited a notable baseline change around 2009, but this has no strong influence on the fit of the flux distribution. While interband flux-flux correlations are found, no stable temporal lags emerge. This implies varying correlation patterns between epochs. The X-ray emission displays a robust harder-when-brighter trend, however with epoch-dependent slopes, while the $\gamma$-ray spectra show only mild flux dependence. The fractional variability increases systematically with energy within a given radiation component. No direct correlation of the year-wise fractional variability with the corresponding average flux could be found. Interestingly, a pronounced X-ray spectral upturn, detected during a low state in 2012, points to an additional radiative component. As the connection from this upturn to the $\gamma$-ray spectrum is not smooth, it probably is not the onset of the inverse-Compton component, but more likely points either to a hadronic contribution or an additional spatially-separate emission zone. These findings reveal the complexity of variability patterns in PKS 2155-304 and the non-uniform nature of its particle acceleration and emission processes.

The waiting time statistics of solar flares provides clues for the underlying physical mechanisms. However, flares occurring on the far-side have been missing in the statistics. In the 2024 May and June, the Solar Orbiter (SolO) spacecraft orbiting behind the Sun, together with near-Earth spacecrafts, provides a unique opportunity to study one of the most flare-productive active regions, NOAA \sar, over its lifetime, as well as the flare occurrence over the entire solar globe. Derived from time intervals between flare peak times, the waiting time distribution (WTD) is fitted by exponential, log-normal, power-law, and \levy functions with the maximum likelihood estimation method. The goodness of fit is evaluated by the Kolmogorov-Smirnov test, and the statistical models are discriminated by information criteria. The major statistical results are: the WTD of flares in the \sar leans towards the log-normal function, while that in the `normal' \rar towards the \levy function; the WTD of global flares defies the local Poisson hypothesis, and its overall profile cannot be reasonably fitted by any of the four candidate distributions, but its power-law tail $\Delta t^{-\alpha}$ is steeper ($\alpha>3$) than the theoretical expectations ($\alpha\le3$), due to the decreased number of long waiting times ($>10^4$ s) and the increased number of shorter waiting times when the far-side flares are taken into account. These results highlight the importance of studying the flare WTD from a global perspective, and suggest that the long-range magnetic connections in the corona may play a role in the flare occurrences.

We present a comprehensive, two-decade, multiwavelength variability study of the blazar PKS 1510-089, one of the most prominent and extensively monitored flat-spectrum radio quasars. Using Fermi-LAT $\gamma$-ray data together with Swift-XRT and UVOT observations spanning 2005-2024, we trace the long-term evolution of its flux, interband correlations, and spectral behaviour across the optical, X-ray, and $\gamma$-ray bands. We find that the HE $\gamma$-ray and X-ray flux distributions are log-normal, while the optical distributions are compatible with double-log-normal functions. The latter may be due to contributions from the accretion disk. The range of fluxes in a given band, as well as the fractional variability values are in-line with the expectations that high-energy parts of a given spectral component are more variable than low-energy parts. No obvious cross-correlations exist between the bands over the 20 years of observations. The X-ray and $\gamma$-ray spectra are variable, but do not show any trend with flux. These results are suggestive of different zones being active in the jet of PKS 1510-089 at any given time. In a previous paper, we used the same techniques to study the high-frequency-peaked BL Lac object PKS 2155-304. Both sources follow the aforementioned trend on the energy-dependent variability of the spectral components, as well as the lack of significant cross-correlations between the studied bands. While PKS 2155-304 exhibits a harder-when-brighter behaviour in its high-energy part of the synchrotron component, no such behaviour could be found in PKS 1510-089. Both sources show orphan flares, which can seemingly happen in any band. In summary, the long-term studies of these two sources reveal that the underlying physics is similar in these apparently different source classes, even though variability patterns keep changing and remain unpredictable.

An astrosphere is a vast, tailed bubble-like volume around a star, formed through the interaction between the stellar magnetic field, the stellar wind, and the interstellar medium (ISM). Detecting and characterizing astrospheres are essential for constraining stellar wind properties, understanding stellar evolution, and assessing the habitability of surrounding exoplanetary systems. Charge exchanges between ionized stellar wind particles and cold ISM hydrogen atoms populate the astrosphere with neutral hydrogen, which can leave observable signatures in the Lyman-{\alpha} (Ly {\alpha}) line absorption profile. Previous studies have inferred stellar mass-loss rates by measuring Ly {\alpha} absorption in stellar spectra caused by astrospheric neutral hydrogen. However, owing to observational limitations, our knowledge of the global morphology of astrospheres remains limited and largely dependent on sometimes contradictory simulation results. Here we investigate the feasibility of detecting Ly {\alpha} emission generated by resonant scattering from neutral hydrogen surrounding the star, enabling the construction of a two-dimensional map of the astrosphere. With a three-dimensional magnetohydrodynamic astrosphere model, we perform forward modelling of the Ly {\alpha} emission and assess the feasibility of this approach by comparing the predicted spectral intensity with the observational limits of the Hubble Space Telescope (HST). Our results indicate that Ly {\alpha} emission from the hydrogen wall is largely absorbed by the ISM, whereas emission from the near-star astrosphere can remain detectable. The spatially resolved circumstellar Ly {\alpha} emission could provide important constraints on the astrospheric configuration and stellar wind properties, such as the standing distance of the bow shock, the symmetry of stellar wind mass loss, and the shape of the astro-tail.

We study the dynamical and collisional evolution of Near-Earth asteroids (NEAs) in Main Belt-crossing orbits (NEACs). We select NEACs with H < 18 and integrate their orbits for 1e7 yr with N-body simulations. Objects are grouped by initial semi-major axis (G1: a < 2.06 au; G2: 2.06 < a < 2.5 au; G3: a > 2.5 au). We compute the fraction of each orbit spent within the main belt (MB), dynamical occupancy maps in the (a,e) plane, and median lifetimes. Using collisional evolution, we obtain size-dependent timescales, the change in the NEA size-frequency distribution (SFD) over 1 Myr, and impactor and crater SFDs on 150 m to 1 km targets, representative of NEAs visited by space missions. Median dynamical lifetimes decrease with increasing a: ~1.3e7 yr (G1), ~2.1e6 yr (G2), and ~0.9e6 yr (G3). NEACs in G2-G3 maintain nearly constant MB residence fractions with short intervals of full containment, while G1 exhibits stronger 0-0.8 oscillations (median ~0.55 for ~1e6 yr). DART-analog impacts occur on ~1e5 yr timescales for targets smaller than about 300 m (rising to ~1e6 yr for larger bodies), whereas catastrophic collisions are negligible within NEAC lifetimes. Over 1 Myr, collisional erosion reduces the meter-size NEA population by only 0.1-1.4% depending on Q_D*. Comparison with the observed crater SFDs on Bennu, Didymos, and Ryugu indicates target strengths of Y ~ 100 Pa for Bennu, young effective surface ages for Didymos, and short crater-retention times of order 1e4-1e5 yr for craters with diameters smaller than 100 m on Ryugu, consistent with rapid resurfacing. NEACs spend a substantial fraction of their lifetimes inside the MB and undergo frequent small-scale impacts, yet collisions weakly modify the global NEA SFD on Myr timescales. Our combined dynamical-collisional framework constrains NEAC lifetimes, orbital pathways, collisional timescales, and surface processing.

Star-disk collisions have been proposed as a promising mechanism for producing quasi-periodic eruptions (QPEs) in galactic nuclei. Because the stellar atmospheric scale height is orders of magnitude smaller than the stellar radius, studying the shock launching by stars poses a significant numerical challenge. We implement an immersed solid-boundary method in Athena++ to study bow-shock formation and ejecta launching when a solid sphere crosses an accretion disk at supersonic speed. After validating the method against experimental results for solid bodies in uniform flows, we perform two- and three-dimensional adiabatic simulations of star-disk collisions. We find that resolving the bow-shock stand-off distance during the compression phase is essential: under-resolved simulations severely underestimate the ejecta mass and energy. When adequately resolved, the ejecta properties agree well with analytical estimates. We further show that collision geometry plays a critical role. Oblique encounters, which arise naturally due to disk rotation, allow easier shock breakout from the disk's backside and substantially reduce the luminosity contrast between forward and backward ejecta compared to perpendicular collisions. These results emphasize the importance of both numerical resolution and three-dimensional geometry in modeling star-disk collisions and interpreting QPEs.

We present an analysis of the short- and long-term optical variability in Van den Bergh 27 (vdB 27), the reflection nebula surrounding RY Tau. The observed variations form a light-echo pattern, with apparent propagation speeds varying across different regions of the nebula and reaching up to approximately 3.6 c, consistent with geometric projection effects. The observed variations in nebular surface brightness are consistent with changes in illumination from the central star.

We present the modules for stellar nucleosynthesis, stellar mass loss, and turbulent diffusion of the new COLIBRE subgrid model for cosmological hydrodynamical simulations of galaxy formation. COLIBRE models the thermal evolution of the multi-phase interstellar medium, dust grains, star formation, and stellar and AGN feedback. This work focuses on the model for chemical enrichment. We track the evolution of 12 chemical elements produced by a broad range of nucleosynthetic channels, including core-collapse supernovae and stellar winds, Type Ia supernovae, and asymptotic giant branch (AGB) stars. Enrichment from $s$- and $r$-process elements is modelled via contributions from AGB stars, neutron star mergers, common envelope supernovae, and collapsars. We present an updated compilation of stellar yields taken from the literature, which we release alongside this work. Small-scale element mixing is implemented through a turbulent diffusion process. While diffusion has only a minimal impact on basic integrated galaxy properties, it does reduce the slope of the gas-phase metallicity-mass relation compared with simulations that do not include it. The distribution of element ratios of individual stellar particles is sensitive to diffusion, but only at low metallicities ($Z \lesssim 10^{-1}\,\rm{Z}_\odot$). The model is tested using redshift $z=0$ results from a set of cosmological simulations, mostly of (25 Mpc)$^3$ volumes, demonstrating generally good agreement with Milky Way stellar abundance trends from the APOGEE survey. The model also reproduces the alpha-element enhancement relations observed in galaxies from SDSS, ATLAS-3D, and the Local Group.

We present a near-infrared abundance analysis of 46 solar analogs with known ages, observed with the WINERED WIDE-mode spectrograph at a resolution of $\lambda/\Delta\lambda = 28,000$. Using an empirically calibrated, line-by-line approach in the $YJ$ bands (0.976--1.089 and 1.182--1.319~{$\mu$}m), we derive abundances for 16 elements. Despite the intrinsic weakness of near-infrared phosphorus diagnostics, the combination of five P\,{\sc i} lines yields a typical uncertainty half-width of $\sim$0.04~dex, providing an estimate of the internal precision over the solar-analog sample. For other elements, the internal precision ranges from $\sim$0.01~dex for Fe and Si to over 0.05--0.14~dex for elements with only a couple of lines available. The resulting per-object abundances for various elements are consistent with previous measurements using high-precision optical spectra with residuals of 0.03--0.2~dex depending on the element. The inferred age--[X/Fe] relations reproduce known trends for the thin disk, while extending them to elements difficult to access in the optical, including P and K. We find the slope of the age--[P/Fe] relation is steeper than that for $\alpha$ elements, which provides an empirical constraint for future modeling of Galactic phosphorus evolution. In addition, we publish a high signal-to-noise (S/N 500--1000) reference spectrum constructed by combining solar-analog spectra, together with the spectra of individual stars, and an empirically calibrated line list with per-line zero-point corrections, for future near-infrared spectroscopic studies.

The direct imaging of potentially habitable exoplanets is one prime science case for high-contrast imaging instruments on extremely large telescopes. Most such exoplanets orbit close to their host stars, where their observation is limited by fast-moving atmospheric speckles and quasi-static non-common-path aberrations (NCPA). Conventional NCPA correction methods often use mechanical mirror probes, which compromise performance during operation. This work presents machine-learning-based NCPA control methods that automatically detect and correct both dynamic and static NCPA errors by leveraging sequential phase diversity. We extend previous work in reinforcement learning for AO to focal plane control. A new model-based RL algorithm, Policy Optimization for NCPAs (PO4NCPA), interprets the focal-plane image as input data and, through sequential phase diversity, determines phase corrections that optimize both non-coronagraphic and post-coronagraphic PSFs without prior system knowledge. Further, we demonstrate the effectiveness of this approach by numerically simulating static NCPA errors on a ground-based telescope and an infrared imager affected by water-vapor-induced seeing (dynamic NCPAs). Simulations show that PO4NCPA robustly compensates static and dynamic NCPAs. In static cases, it achieves near-optimal focal-plane light suppression with a coronagraph and near-optimal Strehl without one. With dynamics NCPA, it matches the performance of the modal least-squares reconstruction combined with a 1-step delay integrator in these metrics. The method remains effective for the ELT pupil, vector vortex coronagraph, and under photon and background noise. PO4NCPA is model-free and can be directly applied to standard imaging as well as to any coronagraph. Its sub-millisecond inference times and performance also make it suitable for real-time low-order correction of atmospheric turbulence beyond HCI.

The coronal magnetic field plays a fundamental role in governing coronal activities, driving space-weather events, and shaping the heliosphere. Due to a lack of direct observations, extrapolation models such as the Potential Field Source Surface (PFSS) model become the primary method to obtain the three-dimensional magnetic field distribution in the corona. However, the PFSS model cannot solve the long-standing open-flux problem, in which the extrapolated open magnetic flux is significantly lower than that inferred from in-situ measurements. To address this issue, we develop an innovative Non-Spherical Potential Field (NSPF) model. The model introduces a Non-Spherical Source Surface (NSSS) defined as an isosurface of the total magnetic field. The NSSS naturally forms concave structures beneath external current sheets, enabling the model to generate substantially more open magnetic flux while yielding a physically plausible distribution of open field regions. As a result, the NSPF model successfully reproduces complex coronal magnetic topologies, interplanetary magnetic field properties, and solar wind source mappings. Our refined coronal magnetic model provides a proper foundation for future research on solar and heliospheric magnetic coupling.

We identify universal signatures in the bispectrum arising from a transient tachyonic instability of entropic fluctuations during inflation, a phenomenon that naturally arises in hyperbolic field-space geometries. We perform exact numerical calculations directly at the level of fluctuations, without relying on a specific background model, and distinguish two cases. In the light case, with masses around the Hubble scale, our results provide the first-ever computation of the bispectrum due to such tachyonic instabilities. We find a universal magnification of the folded configuration, together with the known non-analytic scaling in the squeezed limit. As an illustrative example, we compute and analyse the bispectrum in angular inflation, demonstrating compatibility with current limits. In the heavy case, with masses well above the Hubble scale, the bispectrum exhibits a distinctive correlation between enhanced folded configurations and a `tachyonic resonance' in mildly squeezed limits, with the resonance scale set by the strength of the instability. While the main qualitative features are reproduced, we show that there exists no UV matching for which a single-field effective description, obtained by integrating out the entropic modes, accurately captures the bispectrum for all kinematic configurations. To facilitate observational applications, we introduce simple bispectrum shape templates suitable for current and forthcoming cosmological surveys. Our model-independent results allow for constraining non-standard inflationary attractors characterised by strongly non-geodesic motion.

We have investigated the results for [Fe/H] and distance for a group of 24 globular clusters in the Galactic bulge, employing recent calibrations of RR Lyrae light curves Fourier decomposition and period-absolute magnitude-metallicity (PMZ) calibrations in the I-band. We have limited our calculations to RR Lyrae stars that have been proven to be very likely cluster members. These results are compared with [Fe/H] and Mv (distance) obtained from well-established Fourier calibrations in the V-band. These calibrations of the I-band were found to produce iron values that can differ from the UVES spectroscopic scale by -0.29 to +0.15 dex. The PMZ distances agree within 0.4 kpc with recent solid critical distance compilations. Adopting the newly derived distances, we conducted a spatial and orbital analysis of the bulge globular clusters in a non-axisymmetric Milky Way potential, and compared their orbital properties with earlier studies, finding broadly consistent trends with small systematic differences driven by the assumed distances and Galactic model. Clusters associated with the in situ bulge component display a narrow range low angular momentum and low orbital energies, consistent with formation in the early inner Milky Way.

This overview of the study arXiv:2407.18845, regarding the possibility of generating gravitational waves from a curvature-induced phase transition of a non-minimally coupled scalar dark matter field with a Higgs-portal, was showcased at the "Workshop on Standard Model and Beyond 2025" of the Corfu Summer Institute 2025. The phase transition dynamics during the transition from inflation to kination were calculated for various inflationary scales, considering both positive and negative values of the non-minimal coupling, while also examining the potential for triggering electroweak symmetry breaking. Notably, kination enhances the GW amplitudes, significantly restricting the viable parameter space. While the GW spectra follow the usual rule for high-frequencies from high inflationary scales, certain regions of the parameter space allow for a potential detection with future experiments.

I present the first molecular line survey of the strongly lensed submillimetre galaxy SPT 0027 ($z = 3.44$) using the new Atacama Large Millimeter/submillimeter Array (ALMA) Band~2 receivers (67 - 116 GHz), whose commissioning completes ALMA's full (sub-)millimetre frequency coverage. The broad spectral coverage from 76 to 111 GHz of the observations simultaneously accesses a large suite of molecular and atomic emission lines. I report the novel detections of the hitherto inaccessible CO (3-2) and HNC (4-3) lines, as well as detections of previously-observed CO (4-3) transitions, the neutral carbon line [CI], HCN (5-4), HCO$^{+}$ (5-4), and HNC (5-4), with fluxes in line with previous observations. The CO spectral line energy distribution and [CI]/CO line ratios indicate highly excited, dense molecular gas with a strong far-ultraviolet radiation field. The dense gas fraction is estimated at $17 \pm 9$ per cent, consistent with other dusty star-forming galaxies selected from wide-area surveys. High-resolution Band 7 continuum imaging reveals a clumpy lensed morphology, with star-forming clumps contributing 30-50 per cent of the total emission. With multiple CO lines accessible across a wide redshift range, ALMA Band 2 is uniquely positioned as the premier tool for robust spectroscopic redshifts at Cosmic Noon and beyond ($z \sim 1$-$6$), a capability that will be further enhanced by the Wideband Sensitivity Upgrade's full-band coverage in fewer tunings.

We present an approximate energy-integration method for identifying collisional neutrino flavor instabilities. Direct evaluation of the dispersion relation requires multi-dimensional integrals over neutrino phase space, making systematic searches for unstable modes in numerical models of core-collapse supernovae (CCSNe) and binary neutron star mergers (BNSMs) computationally expensive. In the literature there are some approximate schemes, but they are largely restricted to the homogeneous limit and can exhibit inaccuracies as reported in recent studies. In the current paper, we clarify the origin of the limitations in previous schemes and provide a better approximation method that robustly preserves the key physics of spectral asymmetries and collision rates. It yields a reduced dispersion relation that is inexpensive to evaluate. Comparison with exact solutions demonstrates that our new approximate method shows a good performance in computing both real frequencies and growth rates across a wide range of regimes, including isotropic and anisotropic neutrino distributions for both homogeneous and inhomogeneous modes. This provides a practical, accurate, and scalable framework for identifying collisional flavor instabilities in high-energy astrophysical simulations such as CCSNe and BNSMs.

Modelling structure formation across the full dynamical range of the Universe remains a major challenge in cosmology. This difficulty originates from a fundamental limitation of geodesics in general relativity: a one-parameter family of geodesics can cease to be geodesic at a finite time. This implies that the conventional point-particle approximation is not the primary issue; rather, the breakdown of geodesic flow restricts a consistent description across scales. We develop a covariant multi-scale framework that resolves this problem by decomposing spacetime into hierarchical regions separated by matter horizons. We show how to match shared boundary consistently at the level of the action, leading to a covariant backreaction contribution. The resulting construction provides a first-principles theoretical foundation for cosmological zoom-in simulations and yields an effective energy-momentum tensor capturing the impact of the geometric backreaction effect. As an application, we demonstrate that this backreaction naturally produces flat galaxy rotation curves without invoking an additional dark matter component. Our results establish a new perspective on nonlinear structure formation, in which long dynamical range is resolved through a hierarchy of discrete geodesic domains.

AMBRA combines the large cosmological volume and statistical power of ASTRID with the physically motivated gas-based black hole seeding models from BRAHMA. Motivated by JWST's discoveries of massive black holes (BHs) at $z\gtrsim 9$, AMBRA adopts a lenient heavy-seed prescription from the BRAHMA suite, allowing for the formation of $4\times 10^{4-5}\ M_{\odot}$ seeds in halos with star-forming, metal-poor gas. The seeding model is motivated by scenarios in which heavy seeds form through stellar collisions in star clusters or from the rapid growth of Population III remnants. The improved seeding model enables AMBRA to form BH seeds much earlier and more efficiently compared to ASTRID. This significantly enhances early BH growth, producing a $z=8$ BH number density more than an order of magnitude higher than that in ASTRID over the mass range $10^{5-7}\ M_{\odot}$. BHs reaching masses consistent with GN-z11 and CEERS-1019 typically originate in highly compact density peaks and undergo multiple early mergers. In these systems, $\sim50\%$ of BH masses by $z=11$ is from BH mergers, after which gas accretion becomes the dominant growth channel. Without this early merger-driven assembly, ASTRID cannot reproduce the high-mass BH detected by JWST. Our results indicate that abundant early seed formation combined with frequent mergers can explain several JWST massive BH candidates without requiring sustained super-Eddington accretion. As a testable prediction, AMBRA yields $\approx4$ LISA detectable BH merger events per year at $z\geq8$, which is three orders of magnitude higher than that in ASTRID.

Radio flares have been postulated to be associated with the production of astrophysical neutrinos. For example, TXS 0506+056 exhibits a 2-3 yr delay between the 2017 IceCube-170922A/$\gamma$-ray flare and a GHz radio maximum. We quantitatively test if the delayed radio flare originates from the same compact region where neutrinos and $\gamma$-rays are produced as it expands downstream and synchrotron self-absorption (SSA) is reduced. Starting from the 2017 flare blob parameters, we model the expanding production region and its evolving radio emission with LeHaMoC in a fully time-dependent framework, and compare our 1.2-22 GHz light curves to RATAN-600 data. We study different scenarios with increasing levels of sophistication, including continuous injection and energy re-dissipation on pc scales. While a simple expanding blob scenario fails to reproduce the radio data, a downstream dissipation episode of particles in the optically thin regime, followed by jet deceleration, successfully describes the radio evolution. Within our one-zone time-dependent framework, the delayed radio flare is unlikely to come from an expanding neutrino production zone becoming transparent to radio emission. Additional ingredients are needed, such as re-dissipation downstream with a subsequent Doppler-factor decline. The radio flare is powered by leptonic synchrotron emission and is largely insensitive to the proton population relevant for neutrino production, implying that the delayed radio flare mainly probes downstream dissipation and beaming in certain jet configurations rather than being a genuine feature associated with the neutrino production.

Rotating radio transients (RRATs) represent a significant but poorly understood component of the Galactic neutron star population, characterized by sporadic emission first detectable only through single-pulse searches. We present the RRATalog, an up-to-date catalogue of 335 RRATs, and utilize a uniform sample of RRATs discovered in four Parkes telescope surveys to model their Galactic population. Accounting in detail for observational selection effects, we find a radial density profile similar to pulsars, but identify a significantly steeper luminosity function (power-law index $\alpha \simeq -1.3$) than previously assumed. For sources beaming towards Earth, we estimate $34000 \pm 1600$ potentially observable RRATs above a peak luminosity of 30 mJy kpc$^2$. At these high luminosities, the RRAT population is comparable in size to that of canonical pulsars. Consistent with the observed distribution, the underlying period distribution is significantly shifted toward longer periods compared to canonical pulsars, suggesting RRATs represent a more evolved population. We find evidence for a turnover in the luminosity function below 30 mJy kpc$^2$, and predict that the total number of potentially observable RRATs is $\lesssim 70,000$. Applying the Tauris \& Manchester beaming model, we estimate the total Galactic RRAT population to be $\lesssim 500,000$. The implied birth rate of $\lesssim 1.4$ RRATs per century is consistent with the Galactic core-collapse supernova rate, suggesting RRATs can be reconciled with known progenitor rates without requiring a separate evolutionary origin. We provide predictions for RRAT discoveries in ongoing and future surveys.

Radiation of X-ray pulsars is powered by accretion on the neutron star surface from a binary companion under the influence of a strong magnetic field. We study beaming of this radiation in the case of subcritical X-ray pulsars, where it is formed in the accretion channel close to the neutron star surface. We solve equations of the hydrodynamics and radiative transfer of two coupled polarization modes in the accretion channel numerically, taking into account resonant Compton scattering and vacuum polarization. The beaming patterns are obtained for different accretion rates, photon energies and polarizations, and for different models of the neutron star surface radiation. The calculated beaming patterns are converted into light curves for both the intensity and polarization, taking into account the effects of General Relativity. These beaming patterns and light curves are found to be strongly affected by the resonant Compton scattering for photon energies comparable with the electron cyclotron energy. In particular, the angular redistribution of radiation near the cyclotron resonance may reduce the light-curve modulation amplitude, which is consistent with observational indications of a suppressed pulsed fraction at these energies.

The James Webb Space Telescope (JWST) provides low- to medium-resolution spectra with unprecedented precision and broad near- to mid-infrared wavelength coverage, enabling detailed characterization of exoplanet atmospheres. We present a new JWST NIRISS SOSS transit observation of the warm sub-Saturn HAT-P-12b. Combined with NIRSpec G395M and MIRI LRS data, this enables an assessment of the information content across JWST instruments over the full accessible wavelength range. The NIRISS data were reduced and the impact of reduction choices on the transmission spectrum evaluated. Atmospheric retrievals were performed for all JWST combinations, with selected cases including archival HST data. Four molecules are significantly detected: H2O, CO2, CO, and H2S. Except for H2O, detections require NIRSpec coverage, while H2S is only detected in multi-instrument retrievals. NIRISS SOSS is essential to establish robust evidence for non-gray cloud behavior. A moderate scattering slope (p < 4) is consistently retrieved. Single-instrument retrievals tend to overestimate abundances, whereas combined JWST datasets yield more consistent constraints. The C/O ratio remains sensitive to differences between NIRSpec reductions. Results broadly agree with studies of WASP-39b, but highlight variations in information content across exoplanet types.

The detection of high-energy neutrino signals from the nearby Seyfert galaxy NGC 1068 provides us with a unique opportunity to explore nonthermal processes near the center of supermassive black holes. Using the IceCube and Fermi-LAT data, we present general multimessenger constraints on the energetics of cosmic rays and the compactness of the neutrino emission region (${\mathcal R}$), considering not only $p\gamma$ but also $pp$ processes. Compared to the photohadronic scenario, the hadronuclear scenario can alleviate constraints on the emission region, yielding ${\mathcal R}\lesssim30-70$ for low-$\beta$ plasma and ${\mathcal R}\lesssim5-50$ for high-$\beta$ plasma. While our results support the previous conclusion that the photohadronic scenario favors a compact corona with ${\mathcal R}\sim3-10$, these suggest the relevance of further investigations into $pp$ neutrino contributions. When the cosmic-ray spectrum is extended from 1 GeV, we find that the requred cosmic-ray luminosity exceeds the X-ray luminosity for a spectral index of $s_{\rm CR}\gtrsim2$, which challenges some shock acceleration models. We also show that the beta decay scenario is unlikely even if the magnetic field is as strong as the maximum allowed by the Eddington luminosity. Given that NGC 1068 can be established as a neutrino source, our results will provide evidence for the standard hadronic scenario, including magnetically powered corona models having hard spectra with $s_{\rm CR}\lesssim2$.

In quantum gauge theories, anomaly cancellation severely restricts the allowed patterns of chiral charges. Here we show that, in a phenomenologically motivated framework for light minicharged particles, the anomaly cancellation conditions are equivalent to the degree $k=3$ Prouhet-Tarry-Escott problem in number theory. This correspondence immediately implies that the hidden sector must contain at least four minicharged states. For constructions based on minimal ideal solutions, the mass spectrum generically exhibits a near-degenerate doublet structure, so that the discovery of one minicharged particle would point to a partner state with the same minicharge and a nearby mass. Our results uncover an unexpected link between quantum consistency and number theory, with direct implications for model building and future searches.

Dark energy, the main constituent in our expanding universe, responsible for its acceleration, is currently observed at unprecedented precision by different experiments. While several cosmological models can fit this latest data, deriving some of them from string theory would provide a valuable theoretical prior, with information on the nature of dark energy. This article reviews the efforts towards such a derivation, namely the options from string theory to get a cosmological constant (a de Sitter solution) or a dynamical dark energy (via a quintessence model). After a brief historical perspective, we first review proven or conjectured constraints in getting dark energy from string theory, in classical or asymptotic regimes. Circumventing such obstructions, by changing regime or ansatz, one can try to construct a de Sitter solution: we present a long list of such attempts, and the difficulties encountered. Among them, we discuss in detail efforts towards classical de Sitter solutions. Then, we review quintessence from string theory, focusing on single-field exponential models. Related topics are discussed, including the coupling to matter, the comparison to observational data, and the absence of a cosmological event horizon.

This paper develops an analytical framework for the retarding forces on macroscopic spherical probes travelling through the interstellar medium (ISM) at relativistic speeds (0.1c to 0.99c). Integrating the aberrated momentum flux of both baryonic and radiative fields yields scaling laws that expose what this work calls the Magnitude Paradox: relativistic inertia (gamma^3) keeps a probe's speed nearly constant across parsec-scale distances, yet the same gamma^2 boost to the effective baryonic cross-section drives extreme thermal loading on the hull -- a relativistic correction that becomes significant only above beta > 0.5c and was not quantified in prior work focused on the Starshot regime (beta approx. 0.2c). The central conclusion is that ISM drag is not a kinematic problem -- a probe will not be slowed to a stop -- but a thermodynamic one: the forward surface faces energy deposition rates that no passive material can survive. A closed-form crossover condition is also derived separating the baryonic- and radiative-dominated regimes, showing that for any macroscopic probe in the galactic disk, total radiative drag is negligible by many orders of magnitude.

We study the emission of Cherenkov plasmons by the gas of neutrinos with nonzero temperature and chemical potential. The background plasma, consisting of charged leptons, is taken to be nonrelativistic. The energy emission rate is obtained for longitudinal plasmons. To get the neutrino emissivity we average quantum field theory matrix element over the distribution functions of incoming and outgoing particles. Our results are applied for the description of the cooling down of a neutrino cluster formed in the early universe. Such clusters can exist owing to the neutrino interaction with a hypothetical light scalar boson. Using particular cluster parameters, we demonstrate that the proposed cooling mechanism is efficient for some clusters. We find the temperature range where the proposed cooling channel is valid. Some useful calculations of the polarization tensor, as well as the plasmon form factors and their dispersion relations are also provided.

We present 3D numerical-relativity evolutions of the unstable Ellis-Bronnikov wormhole using GRTeclyn, starting from exact isotropic initial data for the coupled Einstein-phantom-scalar system. With a flat initial lapse (alpha=1) and full phantom support, truncation-level noise eventually drives the rarefactive instability and rapid throat expansion. To force a clean collapse while breaking spherical symmetry, we reduce the phantom stress-energy support to S_support=0.5 and add a quadrupolar scalar-field perturbation (A_phi=+0.02, sigma_phi=0.5). The resulting compressive evolution forms a trapped surface and emits a gravitational-wave signal whose peak propagates between extraction radii at v approx c, distinct from superluminal CCZ4 constraint modes. After horizon formation the swallowed phantom matter triggers a violent rebound ("phantom bounce") that launches an outward curvature shock. For the moderate perturbation amplitude simulated here, an intermediate-mass (10^3 solar mass) wormhole at D=1 Mpc falls slightly below the Advanced LIGO design sensitivity; detection requires either closer sources, larger initial asymmetries, or next-generation detectors.

This document is based on lectures delivered at a recent COSMIC WISPers COST Action training school in Annecy in September 2025. They examine detection of weakly interacting slim particles (WISPs), specifically axions and high-frequency gravitational waves, with compact objects. These slightly expanded notes focus on searches for axion dark matter and axion-like particles with neutron stars, superradiance, white dwarfs and astrophysical searches for high-frequency gravitational waves. They are accompanied by a set of practical exercises. Comments on these notes are gratefully received.

We investigate whether a dynamical wormhole could survive in a universe that undergoes a cosmological bounce. First, the conditions under which a wormhole could persist from a contracting to an expanding phase of the cosmos are presented. Then, the only two known cosmological solutions of Einstein's equations representing wormholes are analyzed, and it is shown that both dynamical wormholes exist for all cosmic times on both sides of a bouncing universe and at the bounce itself. We also provide a detailed analysis of the causal structure of such spacetimes and the matter content of the wormhole. Finally, some possible astrophysical manifestations of surviving wormholes in a bouncing universe are mentioned. Our results show that, at least for the Kim and Pérez-Raia Neto solutions, there is no topology change in the chosen cosmological model with a bounce.

Nuclear metamodels - phenomenological parametrizations of the energy of nuclear matter - are convenient tools to explore the space of realistic neutron star configurations constrained by astrophysical and nuclear data. While much recent work has focused on composition-agnostic barotropic models, the metamodel approach is designed to describe the composition dependence of the relevant thermodynamic potential. We revise a previously proposed non-relativistic metamodel by introducing a more controlled high-density behaviour, improving both its causal properties and its accuracy in reproducing the pressure and the beta-equilibrium composition of microscopically motivated equations of state. Since causality is automatically enforced at high density, the fraction of discarded models due to superluminal sound speeds is substantially reduced, facilitating metamodel-based explorations of equilibrium neutron star configurations. We further assess our framework by performing a Bayesian inference of neutron star properties beyond standard observables such as masses and radii, exploiting the metamodel's ability to probe composition-dependent quantities including the dUrca threshold and the Ledoux criterion for g-mode stability.

If the dark matter mass exceeds the highest temperature of the thermal bath, then dark matter production is Boltzmann suppressed. This opens new possibilities for dark matter model building. In particular, WIMP models that are experimentally excluded can be revived in this setting; conversely, freeze-in models, which would typically be beyond experimental reach, are potentially discoverable in the Boltzmann suppressed regime. In a recent letter, we highlighted these aspects for the case of electroweak doublet fermion dark matter assuming instantaneous inflationary reheating. Due to its elegance and simplicity, we coin this {\em Minimal Freeze-in} (MFI) Dark Matter. Here we consider next-to-minimal extensions of MFI dark matter. We present the implications for non-instantaneous reheating, including scenarios beyond the standard picture in which the Universe is initially matter dominated prior to reheating. Furthermore, we explore model variations within the electroweak dark matter scenario. Specifically, we consider fermion dark matter in higher representations of SU(2)${}_L$, exploring the current limits and the near-future discovery potential.

Quantitative spectroscopic detection of dibromomethane, CH$_2$Br$_2$, for environmental monitoring, workplace safety, and exoplanetary studies is limited by the lack of accurate absorption cross-section data and rigorous spectroscopic models. We report the first high-resolution (6.3 MHz point spacing) absorption cross-section of CH$_2$Br$_2$ in the 1180-1210 cm$^{-1}$ region measured using optical frequency comb Fourier transform spectroscopy. This region is dominated by the strong CH$_2$ wagging ($\nu$$_8$) fundamental vibration, which is about 50 times stronger than the fundamental C-H stretch around 3077 cm$^{-1}$. The measurements resolve isotopologue-specific rovibrational features of CH$_2$$^{79}$Br$^{81}$Br, CH$_2$$^{79}$Br$_2$, and CH$_2$$^{81}$Br$_2$, and we assign rovibrational transitions of the $\nu$$_8$ fundamental and the overlapping $\nu$$_4$+$\nu$$_8$-$\nu$$_4$ hot bands using two methods. First, an empirical non-linear least square fit implemented in PGOPHER provides high-precision line assignment and spectroscopic constants, including accurate band origins, rotational constants, and quartic centrifugal distortion parameters, for the three isotopologues, covering rotational levels up to K$_a$ = 25 and J = 144, with an average RMS residual of 0.00037 cm$^{-1}$ (11.1 MHz). Compared with previously reported band parameters retrieved from a fit to narrowband (1.78 cm$^{-1}$) supersonically cooled spectra (B. E. Brumfield et al., J. Mol. Spectrosc., 2011, 266, 57-62), our fit provides much improved global agreement between measured and simulated spectra. In parallel, an ab initio-based effective Hamiltonian approach was used to model the complete rovibrational polyads, including weak hot-band transitions and polyad interactions inaccessible to purely empirical fits, and provided the first ab initio-based line intensities of CH$_2$Br$_2$ in the 8 $\mu$m spectral region.

We investigate the gravitational wave spectrum from first-order QCD phase transitions using the parity doublet model at finite baryon chemical potential. The model incorporates the chiral invariant mass $m_0$, representing the portion of nucleon mass that persists even when chiral symmetry is restored. Within the model, we identify two first-order phase transition regions: the nuclear liquid--gas transition and the chiral phase transition. By solving the bounce equation and computing the Euclidean action $S_3/T$, we obtain the gravitational wave spectra from both transitions. The liquid--gas transition yields $\alpha \sim \mathcal{O}(1)$ and $\beta/H \sim \mathcal{O}(10)$--$\mathcal{O}(100)$ near the endpoint of the first-order line, producing signals with peak frequencies from the millihertz to the nanohertz band that can fit the existing data. In contrast, the chiral transition produces signals suppressed by approximately five orders of magnitude, well below the sensitivity of all current and planned detectors. These results connect the chiral invariant mass to the gravitational wave spectrum, offering a novel probe of the origin of nucleon mass through gravitational wave astronomy.

We investigate baryogenesis in Standard Model (SM) extensions with new $SU(2)_L$ multiplet fields. We focus on sphalerogenesis, in which the baryon asymmetry of the Universe (BAU) is generated through the gradual decoupling of CP-violating electroweak (EW) sphaleron-like processes. We show that the observed BAU can be reproduced when the new fields possess CP-violating Yukawa interactions, which leave a CP-violating dimension-six operator involving the $SU(2)_L$ gauge fields at low energies. As representative examples, we study models with fermionic $SU(2)_L$ quintuplets and septuplets, and find that these field masses should be $\mathcal{O}(1)\,\mathrm{TeV}$ to explain the BAU. We also show that viable parameter regions for the BAU are consistent with current bounds on the electron electric dipole moment and thoroughly probed by future measurements such as ACME III and by mono-lepton searches at the HL-LHC. Our results provide a concrete and phenomenologically testable ultraviolet completion of sphalerogenesis.

We investigate the coupled dynamics of symmetry breaking and phase separation during quenches across the critical point in a first-order phase transition. Based on the Einstein-Maxwell-scalar theory, we construct a holographic superfluid model with $\mathbb{Z}_2$ symmetry. By introducing higher-order nonlinear terms $\lambda\Psi^4$ and $\tau\Psi^6$ into the scalar field potential, we realize a rich phase structure, which enables us to study the coupling effects between symmetry breaking and phase separation. Furthermore, by preparing initial conditions with well-defined spatial partitions, we discover a new triggering mechanism for the invasion phenomenon, namely that kinks serve as triggering sites for the phase separation process. This study reveals a novel coupling mechanism between topological defects and phase separation, enriches our understanding of nonequilibrium structure formation in strongly coupled systems.

We investigate the dynamical stability and phase transition behavior in a holographic superfluid model incorporating higher-order self-interaction terms $\lambda |\psi|^4$, $\tau|\psi|^6$, and a non-minimal coupling $h(\psi)=e^{\alpha|\psi|^2}$. Thermodynamic and dynamical stability analyzes show that the thermodynamic stability and dynamical stability of the system are consistent. Phase diagram analysis reveals rich critical and supercritical phenomena. For fixed $\lambda<0$ and $\alpha$, increasing $\tau$ shrinks the first-order phase transition region to a critical point and then enters the supercritical region. When varying $\alpha$, the system can exhibit no critical point and, most notably, a double critical phenomenon in which, as $\alpha$ increases, the system first enters the supercritical region and then re-enters the first-order phase transition region. This double critical phenomenon driven by a single parameter is reported for the first time in holographic superfluid models, revealing a complex nonmonotonic coupling effect between the non-minimal coupling and higher-order interaction terms.